Switch fallthrough missing break usbdfu

usbdfu should be updated later...
Fixed bad libopencm3 linker file
2023-01-04 23:41:07 +01:00 · 2023-01-04 23:27:32 +01:00 · 2022-08-11 19:56:31 -07:00 · 2022-08-11 19:45:58 -07:00 · 2022-08-11 19:45:44 -07:00 · 2022-08-11 19:28:10 -07:00
32 changed files with 3049 additions and 128 deletions
--- a/.gitignore
+++ b/.gitignore
@ -16,7 +16,10 @@ tags
 *.b#*
 blackmagic_upgrade
 *.exe
+.DS_Store
 *.elf
 .vscode
+cscope.out
+cscope.files
 .gdb_history
 src/artifacts/
--- a/.gitmodules
+++ b/.gitmodules
@ -1,3 +1,3 @@
 [submodule "libopencm3"]
 	path = libopencm3
-	url = https://github.com/libopencm3/libopencm3.git
+	url = https://github.com/flirc/libopencm3.git
--- a/12
+++ b/12
@ -17,13 +17,23 @@ ifndef NO_LIBOPENCM3
 		git submodule init ;\
 		git submodule update ;\
 	fi
-	$(Q)$(MAKE) $(MFLAGS) -C libopencm3 lib/stm32/f1 lib/stm32/f4 lib/lm4f
+	$(Q)$(MAKE) $(MFLAGS) -C libopencm3 lib/sam/d
 endif
 	$(Q)$(MAKE) $(MFLAGS) -C src

+all_platforms:
+	$(Q)$(MAKE) $(MFLAGS) -C src $@
+
 clean:
 ifndef NO_LIBOPENCM3
 	$(Q)$(MAKE) $(MFLAGS) -C libopencm3 $@
 endif
 	$(Q)$(MAKE) $(MFLAGS) -C src $@

+clang-tidy:
+	$(Q)scripts/run-clang-tidy.py -s "$(PWD)"
+
+clang-format:
+	$(Q)$(MAKE) $(MFLAGS) -C src $@
+
+.PHONY: clean all_platforms clang-tidy clang-format
--- a/README.md
+++ b/README.md
@ -1,113 +1,54 @@
-Black Magic Probe
-=================
-
-[![Discord](https://img.shields.io/discord/613131135903596547?logo=discord)](https://discord.gg/P7FYThy)
-
-Firmware for the Black Magic Debug Probe.
-
-The Black Magic Probe is a modern, in-application debugging tool for
-embedded microprocessors. It allows you see what is going on 'inside' an
-application running on an embedded microprocessor while it executes. It is
-able to control and examine the state of the target microprocessor using a
-JTAG or Serial Wire Debugging (SWD) port and on-chip debug logic provided
-by the microprocessor. The probe connects to a host computer using a
-standard USB interface. The user is able to control exactly what happens
-using the GNU source level debugging software, GDB.
-Serial Wire Output (SWO) allows the target to write tracing and logging to the host
-without using usb or serial port. Decoding SWO in the probe itself
-makes [SWO viewing as simple as connecting to a serial port](https://github.com/blackmagic-debug/blackmagic/wiki/Serial-Wire-Output).
-
-
-Resources
-=========
-
- * [Documentation](https://github.com/blackmagic-debug/blackmagic/wiki)
- * [Binary builds](http://builds.blacksphere.co.nz/blackmagic)
-
-
-Toolchain specific remarks
-==========================
-Most firmware building is done with the most recent suite from https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm.
-If you have a toolchain from other sources and find problems, check if it is a failure of your toolchain and if not open an issue or better provide a pull request with a fix.
-
-OS specific remarks for BMP-Hosted
-==================================
-Most hosted building is done on and for Linux. BMP-hosted for windows can also be build with Mingw on Linux.<br>
-Building hosted for BMP firmware probes only with "make PROBE_HOST HOSTED_BMP_ONLY=1" does not require libusb, libftdi and evt. libhidapi development headers and libraries for running.<br>
-On BSD/Macos, using dev/tty.usbmodemXXX should work but unresolved discussions indicate a hanging open() call on the second invocation. If that happens, try with cu.usbmodemXXX.<br>
-
-Reporting problems
-==================
-Before reporting issues, check against the latest git version. If possible, test against another target /and/or debug probe. Consider broken USB cables and connectors. Try to reproduce with bmp-hosted with at least debug bit 1 set (blackmagic -v 1 ...), as debug messages will be dumped to the starting console. When reporting issues, be as specific as possible!
-
-Sample Session
-=============
-```console
-> arm-none-eabi-gdb gpio.elf
-...<GDB Copyright message>
-(gdb) tar ext /dev/ttyACM0
-Remote debugging using /dev/ttyACM0
-(gdb) mon s
-Target voltage: 2.94V
-Available Targets:
-No. Att Driver
- 1      STM32F40x M3/M4
-(gdb) att 1
-Attaching to program: /devel/en_apps/gpio/f4_discovery/gpio.elf, Remote target
-0x08002298 in UsartIOCtl ()
-(gdb) load
-Loading section .text, size 0x5868 lma 0x8000000
-Loading section .data, size 0x9e0 lma 0x8005868
-Loading section .rodata, size 0x254 lma 0x8006248
-Start address 0x800007c, load size 25756
-Transfer rate: 31 KB/sec, 919 bytes/write.
-(gdb) b main
-Breakpoint 1 at 0x80000e8: file /devel/en_apps/gpio/f4_discovery/../gpio.c, line 70.
-(gdb) r
-Starting program: /devel/en_apps/gpio/f4_discovery/gpio.elf 
-Note: automatically using hardware breakpoints for read-only addresses.
-
-Breakpoint 1, main () at /devel/en_apps/gpio/f4_discovery/../gpio.c:70
-70      {
-```
-
-BLACKMAGIC
+Jeff Probe
 ==========

-You can also build blackmagic as a PC hosted application
-"make PROBE_HOST=hosted"
+This is a fork of the [original Black Magic Probe](https://github.com/blacksphere/blackmagic).

-This builds the same GDB server, that is running on the Black Magic Probe.
-While connection to the Black Magic Probe GDB server is via serial line,
-connection to the PC-Hosted GDB server is via TCP port 2000 for the first
-GDB server and higher for more invokations. Use "tar(get) ext(ented) :2000"
-to connect.
-PC-hosted BMP GDB server can talk to
- Black Magic Probe firmware probes via the USB-serial port
- ST-LinkV2 and V3 with recent firmware
- CMSIS-DAP compatible probes
- JLINK probes
- FTDI MPSSE based probe.
+The original is arguably better, faster and wider supported. However, this 
+project was a way to offer an affordable version and I'll rely on community
+support and pull requests.

-When connected to a single BMP supported probe, starting "blackmagic" w/o any
-arguments starts the server. When several BMP supported probes are connected,
-their types, position and serial number is displayed and the program exits.
-Add "-P (position)" to the next invocation to select one.
-For the setup from the sample session above:
-In another terminal:
-```console
-> blackmagic
-Using 1d50:6018 E2E489E7 Black Sphere Technologies Black Magic Probe (STLINK), (Firmware v1.6.1-477-g70bb131-dirty)
-Remote is Black Magic Probe (STLINK), (Firmware v1.6.1-477-g70bb131-dirty) v1.6.1-477-g70bb131-dirty
-Listening on TCP: 2000
-And in the GDB terminal:
-(gdb) target ext :2000
-Remote debugging using :2000
-(gdb) mon s
-...
+One urguably better funncton is the ability to do DEBUG and Serial communication
+over a single JTAG cable when paired with a device that uses single wire JTAG.
+
+Normally, the serial header can be used on a target for the serial port, and
+shows up as the second serial device on the system, however, we can dynamically
+change the pins to use the ones on the JTAG cable with the following command:
+
+``` bash
+ $ mon convert_tdio enable
 ```

-PC hosted BMP also allows to flash, read and verify a binary file, by default
-starting at lowest flash address. The "-t" argument displays information about the
-connected target. Use "-h " to get a list of supported options.
+Compilation
+---

+Newer toolchains can cause issues. I usually work 4_9-2014q4-20141203 found [here.](https://launchpad.net/gcc-arm-embedded/4.9/4.9-2014-q4-major/+download/gcc-arm-none-eabi-4_9-2014q4-20141203-mac.tar.bz2)
+
+the versionfollowing version
+
+```bash
+ $ make clean
+ $ make PROBE_HOST=jeff CUSTOM_SER=1
+ $ dfu-util --device ,1d50:6017 -s 0x00002000:leave -D src/blackmagic.bin 
+```
+
+CUSTOM OPTIONS
+---
+
+On mac, our device shows up with a serial number /dev/tty.cuJEFF123HDC 
+
+This can be annoy if we want to autocnnect with a gith script. We can override
+the use of a serial number by doing a custom compliation such that our device
+shows up with the following: /dev/cu.usbmodemJEFF1 and /dev/cu.usbmodemJEFF3
+
+```bash
+ $ make PROBE_HOST=jeff CUSTOM_SER=1
+```
+
+More
+---
+
+More helpful information can be found on the black magic probe [readme](https://github.com/blacksphere/blackmagic/blob/master/README.md#black-magic-probe), which is relevant.
+
+See online documentation at https://github.com/blacksphere/blackmagic/wiki
+
+Binaries from the latest automated build can be found on the release page.
--- a/UsingRTT.md
+++ b/UsingRTT.md
@ -0,0 +1,271 @@
+# Using RTT
+
+When debugging arm processors, there are three ways for the target to print debug messages on the host: Semihosting, Serial Wire Output SWO, and Real-Time Transfer RTT.
+
+[Black Magic Probe](https://github.com/blacksphere/blackmagic) (BMP) is an open source debugger probe that already implements Semihosting and Single Wire Output. This patch adds Real-Time Transfer RTT output to usb serial port.
+
+- RTT is implemented, not as a user program, but as a serial port device. To read RTT output, use a terminal emulator and connect to the serial port.
+
+- A novel way to detect RTT automatically, fast and convenient.
+
+## Use
+This example uses linux as operating system. For Windows and MacOS see the *Operating Systems* section.
+
+In one window open a terminal emulator (minicom, putty) and connect to the usb uart:
+```
+$ minicom -c on -D /dev/ttyBmpTarg
+```
+
+In another window open a debugger:
+```
+$ gdb
+(gdb) target extended-remote /dev/ttyBmpGdb
+(gdb) monitor swdp_scan
+(gdb) attach 1
+(gdb) monitor rtt
+(gdb) run
+^C
+(gdb) monitor rtt status
+rtt: on found: yes ident: off halt: off channels: auto 0 1 3
+max poll ms: 256 min poll ms: 8 max errs: 10
+```
+
+The terminal emulator displays RTT output from the target,
+and characters typed in the terminal emulator are sent via RTT to the target.
+
+
+## gdb commands
+
+The following new gdb commands are available:
+
+- ``monitor rtt``
+
+	switch rtt on
+
+- ``monitor rtt enable``
+
+	switch rtt on
+
+- ``monitor rtt disable``
+
+	switch rtt off
+
+- ``monitor rtt poll `` max_poll_ms min_poll_ms max_errs
+
+	sets maximum time between polls, minimum time between polls, and the maximum number of errors before RTT disconnects from the target. Times in milliseconds. It is best if max_poll_ms/min_poll_ms is a power of two. As an example, if you wish to check for RTT output between once per second to eight times per second: ``monitor rtt poll 1000 125 10``.
+
+- ``monitor rtt status``
+
+	show status.
+
+rtt|found|state
+---|---|---
+rtt: off|found: no|rtt inactive
+rtt: on|found: no|searching for rtt control block
+rtt: on|found: yes|rtt active
+rtt: off|found: yes|corrupt rtt control block, or target memory access error
+
+A status of `rtt: on found: no` indicates bmp is still searching for the rtt control block in target ram, but has not found anything yet. A status of  `rtt: on found: yes` indicates the control block has been found and rtt is active.
+
+- ``monitor rtt channel``
+
+	enables the first two output channels, and the first input channel. (default)
+
+- ``monitor rtt channel number...``
+
+	enables the given RTT channel numbers. Channels are numbers from 0 to 15, inclusive. Eg. ``monitor rtt channel 0 1 4`` to enable channels 0, 1, and 4.
+
+- ``monitor rtt ident string``
+
+	sets RTT ident to *string*. If *string* contains a space, replace the space with an underscore _. Setting ident string is optional, RTT works fine without.
+
+- ``monitor rtt ident``
+
+	clears ident string. (default)
+
+- ``monitor rtt cblock``
+
+	shows rtt control block data, and which channels are enabled. This is an example control block:
+	
+```
+(gdb) mon rtt cb
+cbaddr: 0x200000a0
+ch ena cfg i/o buf@        size head@      tail@      flg
+ 0   y   y out 0x20000148  1024 0x200000c4 0x200000c8   2
+ 1   y   n out 0x00000000     0 0x200000dc 0x200000e0   0
+ 2   n   n out 0x00000000     0 0x200000f4 0x200000f8   0
+ 3   y   y in  0x20000548    16 0x2000010c 0x20000110   0
+ 4   n   n in  0x00000000     0 0x20000124 0x20000128   0
+ 5   n   n in  0x00000000     0 0x2000013c 0x20000140   0
+ 6   n   n in  0x00000000     0 0x00000000 0x00000000   0
+ 7   n   n in  0x00000000     0 0x00000000 0x00000000   0
+ 8   n   n in  0x00000000     0 0x00000000 0x00000000   0
+ 9   n   n in  0x00000000     0 0x00000000 0x00000000   0
+10   n   n in  0x00000000     0 0x00000000 0x00000000   0
+11   n   n in  0x00000000     0 0x00000000 0x00000000   0
+12   n   n in  0x00000000     0 0x00000000 0x00000000   0
+13   n   n in  0x00000000     0 0x00000000 0x00000000   0
+14   n   n in  0x00000000     0 0x00000000 0x00000000   0
+15   n   n in  0x00000000     0 0x00000000 0x00000000   0
+```
+
+Channels are listed, one channel per line. The columns are: channel, enabled, configured, input/output, buffer address, buffer size, address of head pointer, address of tail pointer, flag. Each channel is a circular buffer with head and tail pointer.
+	
+Note the columns `ena` for enabled, `cfg` for configured.
+	
+Configured channels have a non-zero buffer address and non-zero size.  Configured channels are marked  yes `y` in the column `cfg` . What channels are configured depends upon target software.
+	
+Channels the user wants to see are marked yes `y` in the column enabled `ena`. The user can change which channels are shown with the `monitor rtt channel` command.
+
+Output channels are displayed, and Input channels receive keyboard input, if they are marked yes in both *enabled* and *configured*.
+
+The control block is cached for speed. In an interrupted program, `monitor rtt` will force a reload of the control block when the program continues.
+
+## Identifier string
+It is possible to set an RTT identifier string.
+As an example, if the RTT identifier is "IDENT STR":
+```
+$ gdb
+(gdb) target extended-remote /dev/ttyBmpGdb
+(gdb) monitor swdp_scan
+(gdb) attach 1
+(gdb) monitor rtt ident IDENT_STR
+(gdb) monitor rtt
+(gdb) run
+^C
+(gdb) monitor rtt status
+rtt: on found: yes ident: "IDENT STR" halt: off channels: auto 0 1 3
+max poll ms: 256 min poll ms: 8 max errs: 10
+```
+Note replacing space with underscore _ in *monitor rtt ident*.
+
+Setting an identifier string is optional. RTT gives the same output at the same speed, with or without specifying identifier string.
+
+## Operating systems
+
+[Configuration](https://github.com/blacksphere/blackmagic/wiki/Getting-Started) instructions for windows, linux and macos.
+
+### Windows
+
+After configuration, Black Magic Probe shows up in Windows as two _USB Serial (CDC)_ ports.
+
+Connect arm-none-eabi-gdb, the gnu debugger for arm processors, to the lower numbered of the two COM ports. Connect an ansi terminal emulator to the higher numbered of the two COM ports.
+
+Sample gdb session:
+```
+(gdb) target extended-remote COM3
+(gdb) monitor swdp_scan
+(gdb) attach 1
+(gdb) monitor rtt
+(gdb) run
+```
+
+For COM port COM10 and higher, add the prefix `\\.\`, e.g.
+```
+target extended-remote \\.\COM10
+```
+
+Target RTT output will appear in the terminal, and what you type in the terminal will be sent to the RTT input of the target.
+
+### linux
+On linux, install [udev rules](https://github.com/blacksphere/blackmagic/blob/master/driver/99-blackmagic.rules). Disconnect and re-connect the BMP. Check the device shows up in /dev/ :
+```
+$ ls -l /dev/ttyBmp*
+lrwxrwxrwx 1 root root 7 Dec 13 07:29 /dev/ttyBmpGdb -> ttyACM0
+lrwxrwxrwx 1 root root 7 Dec 13 07:29 /dev/ttyBmpTarg -> ttyACM2
+```
+Connect terminal emulator to /dev/ttyBmpTarg and gdb to /dev/ttyBmpGdb .
+
+In one window:
+```
+minicom -c on -D /dev/ttyBmpTarg
+```
+In another window :
+```
+gdb
+(gdb) target extended-remote /dev/ttyBmpGdb
+(gdb) monitor swdp_scan
+(gdb) attach 1
+(gdb) monitor rtt
+(gdb) run
+```
+
+### MacOS
+
+On MacOS the tty devices have different names than on linux. On connecting blackmagic to the computer 4 devices are created, 2 'tty' and 2 'cu' devices. Gdb connects to the first cu device (e.g.: `target extended-remote /dev/cu.usbmodemDDCEC9EC1`), while RTT is connected to the second tty device (`minicom -c on -D /dev/tty.usbmodemDDCEC9EC3`). In full:
+
+In one Terminal window, connect a terminal emulator to /dev/tty.usbmodemDDCEC9EC3 :
+
+```
+minicom -c on -D /dev/tty.usbmodemDDCEC9EC3
+```
+In another Terminal window, connect gdb to /dev/cu.usbmodemDDCEC9EC1 :
+```
+gdb
+(gdb) target extended-remote /dev/cu.usbmodemDDCEC9EC1
+(gdb) monitor swdp_scan
+(gdb) attach 1
+(gdb) monitor rtt
+(gdb) run
+```
+RTT input/output is in the window running _minicom_.
+
+## Notes
+
+- Design goal was smallest, simplest implementation that has good practical use.
+
+- RTT code size is 3.5 kbyte - the whole debugger 110 kbyte.
+
+- Because RTT is implemented as a serial port device, there is no need to write and maintain software for different host operating systems. A serial port works everywhere - linux, windows and mac. You can even use an Android mobile phone as RTT terminal.
+
+- Because polling occurs between debugger probe and target, the load on the host is small. There is no constant usb traffic, there are no real-time requirements on the host.
+
+- RTT polling frequency is adaptive and goes up and down with RTT activity. Use *monitor rtt poll* to balance response speed and target load for your use.
+
+- Detects RTT automatically, very convenient.
+
+- When using RTT as a terminal, sending data from host to target, you may need to change local echo, carriage return and/or line feed settings in your terminal emulator.
+
+- Architectures such as risc-v may not allow the debugger access to target memory while the target is running. As a workaround, on these architectures RTT briefly halts the target during polling. If the target is halted during polling, `monitor rtt status` shows `halt: on`.
+
+- Measured RTT speed.
+
+| debugger                  | char/s |
+| ------------------------- | ------ |
+| bmp stm32f723 stlinkv3    | 49811  |
+| bmp stm32f411 black pill  | 50073  |
+| bmp stm32f103 blue pill   | 50142  |
+
+This is the speed at which characters can be sent from target to debugger probe, in reasonable circumstances. Test target is an stm32f103 blue pill running an [Arduino sketch](https://github.com/koendv/Arduino-RTTStream/blob/main/examples/SpeedTest/SpeedTest.ino). Default *monitor rtt poll* settings on debugger. Default RTT buffer size in target and debugger. Overhead for printf() calls included.
+
+## Compiling firmware
+To compile with RTT support, add *ENABLE_RTT=1*.
+
+Eg. for STM32F103 blue pill:
+```
+make clean
+make PROBE_HOST=stlink ENABLE_RTT=1
+```
+or for the STM32F411 *[Black Pill](https://www.aliexpress.com/item/1005001456186625.html)*:
+```
+make clean
+make PROBE_HOST=f4discovery BLACKPILL=1 ENABLE_RTT=1
+```
+Setting an ident string is optional. But if you wish, you can set the default RTT ident at compile time.
+For STM32F103 *Blue Pill*:
+```
+make clean
+make PROBE_HOST=stlink ENABLE_RTT=1 "RTT_IDENT=IDENT\ STR"
+```
+or for STM32F411 *Black Pill*:
+```
+make clean
+make PROBE_HOST=f4discovery BLACKPILL=1 ENABLE_RTT=1 "RTT_IDENT=IDENT\ STR"
+```
+Note the backslash \\ before the space.
+
+## Links
+ - [OpenOCD](https://openocd.org/doc/html/General-Commands.html#Real-Time-Transfer-_0028RTT_0029)
+ - [probe-rs](https://probe.rs/) and [rtt-target](https://github.com/mvirkkunen/rtt-target) for the _rust_ programming language.
+ - [RTT Stream](https://github.com/koendv/Arduino-RTTStream) for Arduino on arm processors
+ - [\[WIP\] RTT support - PR from katyo](https://github.com/blacksphere/blackmagic/pull/833)
--- a/driver/99-blackmagic.rules
+++ b/driver/99-blackmagic.rules
@ -1,6 +1,7 @@
 # Black Magic Probe
 # there are two connections, one for GDB and one for UART debugging
 # copy this to /etc/udev/rules.d/99-blackmagic.rules
+# and run /usr/sbin/udevadm control --reload-rules
 SUBSYSTEM=="tty", ACTION=="add", ATTRS{interface}=="Black Magic GDB Server", SYMLINK+="ttyBmpGdb"
 SUBSYSTEM=="tty", ACTION=="add", ATTRS{interface}=="Black Magic UART Port", SYMLINK+="ttyBmpTarg"
 SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ATTR{idVendor}=="1d50", ATTR{idProduct}=="6017", MODE="0666"
--- a/2
+++ b/2
@ -1 +1 @@
-Subproject commit 8435287300e5ca9af9f889c529e7b1fa019c42fb
+Subproject commit 63573143ef7e1b037d1f0c5baedc5264e12562b8
--- a/schematic/bm-sam-a04.pdf
+++ b/schematic/bm-sam-a04.pdf
--- a/src/Makefile
+++ b/src/Makefile
@ -9,7 +9,7 @@ Q := @
 endif

 CFLAGS += -Wall -Wextra -Werror -Wno-char-subscripts \
-	-std=gnu99 -g3 -MD -I./target \
+	-std=gnu99 -MD -I./target \
 	-I. -Iinclude -I$(PLATFORM_DIR)

 ifeq ($(ENABLE_DEBUG), 1)
@ -65,11 +65,6 @@ SRC =			\

 include $(PLATFORM_DIR)/Makefile.inc

-ifneq ($(PC_HOSTED),1)
-# Output memory usage information
-LDFLAGS += -Wl,--print-memory-usage
-endif
-
 OPT_FLAGS ?= -Os
 CFLAGS += $(OPT_FLAGS)
 LDFLAGS += $(OPT_FLAGS)
@ -95,8 +90,28 @@ VPATH += platforms/common
 CFLAGS += -Iplatforms/common
 endif

+ifeq ($(ENABLE_RTT), 1)
+CFLAGS += -DENABLE_RTT
+SRC += rtt.c rtt_if.c
+endif
+
+ifdef RTT_IDENT
+CFLAGS += -DRTT_IDENT=$(RTT_IDENT)
+endif
+
 OBJ = $(patsubst %.S,%.o,$(patsubst %.c,%.o,$(SRC)))

+OPTIMIZE := swdptap.o jtagtap.o \
+	    adiv5_jtagdp.o adiv5_swdp.o adiv5.o \
+	    cortexa.o cortexm.o \
+	    gdb_if.o gdb_main.o gdb_hostio.o gdb_packet.o \
+	    jtag_devs.o jtag_scan.o \
+	    crc32.o main.o \
+	    cdcacm.o jeff.o timing.o traceswo.o usbuart.o \
+
+$(OPTIMIZE)::        CFLAGS := $(filter-out -Os, $(CFLAGS))
+$(OPTIMIZE)::        CFLAGS += -O3
+
 $(TARGET): include/version.h $(OBJ)
 	@echo "  LD      $@"
 	$(Q)$(CC) -o $@ $(OBJ) $(LDFLAGS)
@ -112,14 +127,14 @@ $(TARGET): include/version.h $(OBJ)
 ifndef PC_HOSTED
 %.bin:	%.elf
 	@echo "  OBJCOPY $@"
-	$(Q)$(OBJCOPY) -O binary $^ $@
+	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) -O binary $^ $@

 %.hex:	%.elf
 	@echo "  OBJCOPY $@"
 	$(Q)$(OBJCOPY) -O ihex $^ $@
 endif

-.PHONY:	clean host_clean all_platforms FORCE
+.PHONY:	clean host_clean all_platforms clang-format FORCE

 clean:	host_clean
 	$(Q)echo "  CLEAN"
@ -127,16 +142,27 @@ clean:	host_clean
 	-$(Q)$(RM) platforms/*/*.o platforms/*/*.d mapfile include/version.h

 all_platforms:
+	$(Q)if [ ! -f ../libopencm3/Makefile ]; then \
+		echo "Initialising git submodules..." ;\
+		git submodule init ;\
+		git submodule update ;\
+	fi
+	$(Q)$(MAKE) $(MFLAGS) -C ../libopencm3 lib/stm32/f1 lib/stm32/f4 lib/lm4f
 	$(Q)set -e ;\
 	mkdir -p artifacts/$(shell git describe --always --dirty --tags) ;\
 	echo "<html><body><ul>" > artifacts/index.html ;\
+	$(MAKE) clean ;\
 	for i in platforms/*/Makefile.inc ; do \
 		export DIRNAME=`dirname $$i` ;\
 		export PROBE_HOST=`basename $$DIRNAME` ;\
 		export CFLAGS=-Werror ;\
 		echo "Building for hardware platform: $$PROBE_HOST" ;\
-		$(MAKE) clean ;\
 		$(MAKE);\
+		if [ -f blackmagic ]; then \
+			mv blackmagic artifacts/blackmagic-$$PROBE_HOST ;\
+			echo "<li><a href='blackmagic-$$PROBE_HOST'>$$PROBE_HOST</a></li>"\
+				>> artifacts/index.html ;\
+		fi ;\
 		if [ -f blackmagic.bin ]; then \
 			mv blackmagic.bin artifacts/blackmagic-$$PROBE_HOST.bin ;\
 			echo "<li><a href='blackmagic-$$PROBE_HOST.bin'>$$PROBE_HOST</a></li>"\
@ -147,13 +173,31 @@ all_platforms:
 			echo "<li><a href='blackmagic_dfu-$$PROBE_HOST.bin'>$$PROBE_HOST DFU</a></li>"\
 				>> artifacts/index.html ;\
 		fi ;\
+		$(MAKE) clean ;\
 	done ;\
 	echo "</ul></body></html>" >> artifacts/index.html ;\
-	cp artifacts/*.bin artifacts/$(shell git describe --always --dirty --tags)
+	cp artifacts/blackmagic* artifacts/$(shell git describe --always --dirty --tags)

 command.c: include/version.h

+GIT_VERSION := $(shell git describe --always --dirty --tags)
+VERSION_HEADER := \#define FIRMWARE_VERSION "$(GIT_VERSION)"
+
 include/version.h: FORCE
-	$(Q)echo " GIT include/version.h"
-	$(Q)echo "#define FIRMWARE_VERSION \"$(shell git describe --always --dirty --tags)\"" > $@
+	@# If git isn't found then GIT_VERSION will be an empty string.
+ifeq ($(GIT_VERSION),)
+	@echo Git not found, assuming up to date include/version.h
+else
+	@# Note that when we echo the version to the header file, echo writes a final newline
+	@# to the file. This is fine and probably makes the file more human-readable, but
+	@# also means we have to account for that newline in this comparison.
+	$(Q)if [ ! -f $@ ] || [ "$$(cat $@)" != "$$(echo '$(VERSION_HEADER)\n')" ]; then \
+		echo " GEN $@"; \
+		echo '$(VERSION_HEADER)' > $@; \
+	fi
+endif
+
+clang-format:
+	$(Q)clang-format -i *.c */*.c */*/*.c *.h */*.h */*/*.h
+
 -include *.d
--- a/src/command.c
+++ b/src/command.c
@ -34,11 +34,18 @@
 #include "version.h"
 #include "serialno.h"

+#ifdef ENABLE_RTT
+#include "rtt.h"
+#endif
+
 #ifdef PLATFORM_HAS_TRACESWO
 #	include "traceswo.h"
 #endif

 static bool cmd_version(target *t, int argc, char **argv);
+#ifdef PLATFORM_HAS_PRINTSERIAL
+static bool cmd_serial(target *t, int argc, char **argv);
+#endif
 static bool cmd_help(target *t, int argc, char **argv);

 static bool cmd_jtag_scan(target *t, int argc, char **argv);
@ -56,12 +63,25 @@ static bool cmd_target_power(target *t, int argc, const char **argv);
 static bool cmd_traceswo(target *t, int argc, const char **argv);
 #endif
 static bool cmd_heapinfo(target *t, int argc, const char **argv);
+#ifdef ENABLE_RTT
+static bool cmd_rtt(target *t, int argc, const char **argv);
+#endif
 #if defined(PLATFORM_HAS_DEBUG) && (PC_HOSTED == 0)
 static bool cmd_debug_bmp(target *t, int argc, const char **argv);
 #endif
+#ifdef PLATFORM_HAS_UART_WHEN_SWDP
+static bool cmd_convert_tdio(target *t, int argc, const char **argv);
+static bool cmd_set_srst(target *t, int argc, const char **argv);
+#endif
+#ifdef PLATFORM_HAS_BOOTLOADER
+static bool cmd_enter_bootldr(target *t, int argc, const char **argv);
+#endif

 const struct command_s cmd_list[] = {
 	{"version", (cmd_handler)cmd_version, "Display firmware version info"},
+#ifdef PLATFORM_HAS_PRINTSERIAL
+	{"serial", (cmd_handler)cmd_serial, "Display firmware serial number"},
+#endif
 	{"help", (cmd_handler)cmd_help, "Display help for monitor commands"},
 	{"jtag_scan", (cmd_handler)cmd_jtag_scan, "Scan JTAG chain for devices" },
 	{"swdp_scan", (cmd_handler)cmd_swdp_scan, "Scan SW-DP for devices" },
@ -74,6 +94,9 @@ const struct command_s cmd_list[] = {
 #ifdef PLATFORM_HAS_POWER_SWITCH
 	{"tpwr", (cmd_handler)cmd_target_power, "Supplies power to the target: (enable|disable)"},
 #endif
+#ifdef ENABLE_RTT
+	{"rtt", (cmd_handler)cmd_rtt, "enable|disable|status|channel 0..15|ident (str)|cblock|poll maxms minms maxerr" },
+#endif
 #ifdef PLATFORM_HAS_TRACESWO
 #if defined TRACESWO_PROTOCOL && TRACESWO_PROTOCOL == 2
 	{"traceswo", (cmd_handler)cmd_traceswo, "Start trace capture, NRZ mode: (baudrate) (decode channel ...)" },
@ -84,6 +107,13 @@ const struct command_s cmd_list[] = {
 	{"heapinfo", (cmd_handler)cmd_heapinfo, "Set semihosting heapinfo" },
 #if defined(PLATFORM_HAS_DEBUG) && (PC_HOSTED == 0)
 	{"debug_bmp", (cmd_handler)cmd_debug_bmp, "Output BMP \"debug\" strings to the second vcom: (enable|disable)"},
+#endif
+#ifdef PLATFORM_HAS_UART_WHEN_SWDP
+	{"convert_tdio", (cmd_handler)cmd_convert_tdio,"Switch TDI/O pins to UART TX/RX functions"},
+	{"set_srst", (cmd_handler)cmd_set_srst,"Set output state of SRST pin (enable|disable)"},
+#endif
+#ifdef PLATFORM_HAS_BOOTLOADER
+	{"enter_bootldr", (cmd_handler)cmd_enter_bootldr,"Force BMP into bootloader mode"},
 #endif
 	{NULL, NULL, NULL}
 };
@ -410,6 +440,82 @@ static bool cmd_target_power(target *t, int argc, const char **argv)
 }
 #endif

+#ifdef ENABLE_RTT
+static const char *on_or_off(const bool value)
+{
+	return value ? "on" : "off";
+}
+
+static bool cmd_rtt(target *t, int argc, const char **argv)
+{
+	(void)t;
+	const size_t command_len = strlen(argv[1]);
+	if (argc == 1 || (argc == 2 && !strncmp(argv[1], "enabled", command_len))) {
+		rtt_enabled = true;
+		rtt_found = false;
+	} else if ((argc == 2) && !strncmp(argv[1], "disabled", command_len)) {
+		rtt_enabled = false;
+		rtt_found = false;
+	} else if ((argc == 2) && !strncmp(argv[1], "status", command_len)) {
+		gdb_outf("rtt: %s found: %s ident: \"%s\"", on_or_off(rtt_enabled), rtt_found ? "yes" : "no",
+			rtt_ident[0] == '\0' ? "off" : rtt_ident);
+		gdb_outf(" halt: %s", on_or_off(target_no_background_memory_access(t)));
+		gdb_out(" channels: ");
+		if (rtt_auto_channel)
+			gdb_out("auto ");
+		for (size_t i = 0; i < MAX_RTT_CHAN; i++) {
+			if (rtt_channel[i].is_enabled)
+				gdb_outf("%d ", i);
+		}
+		gdb_outf(
+			"\nmax poll ms: %u min poll ms: %u max errs: %u\n", rtt_max_poll_ms, rtt_min_poll_ms, rtt_max_poll_errs);
+	} else if (argc >= 2 && !strncmp(argv[1], "channel", command_len)) {
+		/* mon rtt channel switches to auto rtt channel selection
+		   mon rtt channel number... selects channels given */
+		for (size_t i = 0; i < MAX_RTT_CHAN; i++)
+			rtt_channel[i].is_enabled = false;
+
+		if (argc == 2)
+			rtt_auto_channel = true;
+		else {
+			rtt_auto_channel = false;
+			for (size_t i = 2; i < (size_t)argc; ++i) {
+				const uint32_t channel = strtoul(argv[i], NULL, 0);
+				if (channel < MAX_RTT_CHAN)
+					rtt_channel[channel].is_enabled = true;
+			}
+		}
+	} else if (argc == 2 && !strncmp(argv[1], "ident", command_len))
+		rtt_ident[0] = '\0';
+	else if (argc == 2 && !strncmp(argv[1], "poll", command_len))
+		gdb_outf("%u %u %u\n", rtt_max_poll_ms, rtt_min_poll_ms, rtt_max_poll_errs);
+	else if (argc == 2 && !strncmp(argv[1], "cblock", command_len)) {
+		gdb_outf("cbaddr: 0x%x\n", rtt_cbaddr);
+		gdb_out("ch ena cfg i/o buf@        size head@      tail@      flg\n");
+		for (size_t i = 0; i < MAX_RTT_CHAN; ++i) {
+			gdb_outf("%2zu   %c   %c %s 0x%08x %5d 0x%08x 0x%08x   %d\n", i, rtt_channel[i].is_enabled ? 'y' : 'n',
+				rtt_channel[i].is_configured ? 'y' : 'n', rtt_channel[i].is_output ? "out" : "in ",
+				rtt_channel[i].buf_addr, rtt_channel[i].buf_size, rtt_channel[i].head_addr, rtt_channel[i].tail_addr,
+				rtt_channel[i].flag);
+		}
+	} else if (argc == 3 && !strncmp(argv[1], "ident", command_len)) {
+		strncpy(rtt_ident, argv[2], sizeof(rtt_ident));
+		rtt_ident[sizeof(rtt_ident) - 1] = '\0';
+		for (size_t i = 0; i < sizeof(rtt_ident); i++) {
+			if (rtt_ident[i] == '_')
+				rtt_ident[i] = ' ';
+		}
+	} else if (argc == 5 && !strncmp(argv[1], "poll", command_len)) {
+		/* set polling params */
+		rtt_max_poll_ms = strtoul(argv[2], NULL, 0);
+		rtt_min_poll_ms = strtoul(argv[3], NULL, 0);
+		rtt_max_poll_errs = strtoul(argv[4], NULL, 0);
+	} else
+		gdb_out("what?\n");
+	return true;
+}
+#endif
+
 #ifdef PLATFORM_HAS_TRACESWO
 static bool cmd_traceswo(target *t, int argc, const char **argv)
 {
@ -487,6 +593,66 @@ static bool cmd_debug_bmp(target *t, int argc, const char **argv)
 	return true;
 }
 #endif
+
+#ifdef PLATFORM_HAS_UART_WHEN_SWDP
+static bool cmd_convert_tdio(target *t, int argc, const char **argv)
+{
+        (void)t;
+
+	uint8_t val;
+	if (argc > 1) {
+		val = (!strcmp(argv[1], "enable")) ? true : false;
+		usbuart_convert_tdio(val);
+	} else {
+		gdb_outf("Convert_tdio: %s\n",(usbuart_convert_tdio_enabled()) ?
+				"enabled" : "disabled");
+	}
+
+	return true;
+}
+
+static bool cmd_set_srst(target *t, int argc, const char **argv)
+{
+	(void) t;
+
+	uint8_t val;
+	if (argc > 1) {
+		val = (!strcmp(argv[1], "enable")) ? true : false;
+		platform_srst_set_val(val);
+	} else {
+		gdb_outf("SRST: %s\n",(platform_srst_get_val()) ?
+				"enabled" : "disabled");
+	}
+
+	return true;
+}
+#endif
+
+#ifdef PLATFORM_HAS_BOOTLOADER
+static bool cmd_enter_bootldr(target *t, int argc, const char **argv)
+{
+	(void) t;
+	(void) argc;
+	(void) argv;
+
+	scb_reset_system();
+
+	return true;
+}
+#endif
+
+#ifdef PLATFORM_HAS_PRINTSERIAL
+bool cmd_serial(target *t, int argc, char **argv)
+{
+	(void) t;
+	(void) argc;
+	(void) argv;
+
+	print_serial();
+	return true;
+}
+#endif
+
 static bool cmd_heapinfo(target *t, int argc, const char **argv)
 {
 	if (t == NULL) gdb_out("not attached\n");
--- a/src/gdb_main.c
+++ b/src/gdb_main.c
@ -35,6 +35,9 @@
 #include "command.h"
 #include "crc32.h"
 #include "morse.h"
+#ifdef ENABLE_RTT
+#include "rtt.h"
+#endif

 enum gdb_signal {
 	GDB_SIGINT = 2,
@ -208,8 +211,12 @@ int gdb_main_loop(struct target_controller *tc, bool in_syscall)
 			/* Wait for target halt */
 			while(!(reason = target_halt_poll(cur_target, &watch))) {
 				char c = (char)gdb_if_getchar_to(0);
-				if(c == '\x03' || c == '\x04')
+				if(c == '\x03' || c == '\x04') {
 					target_halt_request(cur_target);
+				}
+				#ifdef ENABLE_RTT
+				if (rtt_enabled) poll_rtt(cur_target);
+				#endif
 			}
 			SET_RUN_STATE(0);

@ -580,6 +587,10 @@ static void handle_v_packet(char *packet, const size_t plen)
 			}
 			break;
 		}
+		#ifdef ENABLE_RTT
+		/* force searching rtt control block */
+		rtt_found = false;
+		#endif
 		/* Run target program. For us (embedded) this means reset. */
 		if (cur_target) {
 			target_set_cmdline(cur_target, cmdline);
--- a/src/include/queue.h
+++ b/src/include/queue.h
@ -0,0 +1,85 @@
+/*
+ * Copyright 2018 Robert C. Curtis. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above
+ *       copyright notice, this list of conditions and the following
+ *       disclaimer in the documentation and/or other materials
+ *       provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ROBERT C. CURTIS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ROBERT C. CURTIS OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+ * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * The views and conclusions contained in the software and documentation
+ * are those of the authors and should not be interpreted as representing
+ * official policies, either expressed or implied, of Robert C. Curtis.
+ */
+
+/** @file util/queue.h
+ * Static queue primitives.
+ *
+ * This file contains a set of static queue primitives that are common among
+ * all of the low level queue implementations. The primitives are inline
+ * functions, and will be optimal if size is a constant power of 2.
+ */
+
+#ifndef I__QUEUE_H__
+	#define I__QUEUE_H__
+
+/** Increment a queue index.
+ * @param[in]	idx	Queue index
+ * @param[in]	size	Queue size
+ * @returns	The new queue index value
+ */
+static inline size_t qinc(size_t idx, size_t size)
+{
+	return ((idx + 1) % size);
+}
+
+/** Decrement a queue index.
+ * @param[in]	idx	Queue index
+ * @param[in]	size	Queue size
+ * @returns	The new queue index value
+ */
+static inline size_t qdec(size_t idx, size_t size)
+{
+	return ((idx - 1) % size);
+}
+
+/** Tests if a queue is full.
+ * @param[in]	head	Head index
+ * @param[in]	tail	Tail index
+ * @param[in]	size	Queue size
+ */
+static inline int qfull(size_t head, size_t tail, size_t size)
+{
+	size_t next_head = qinc(head, size);
+	return (next_head == tail);
+}
+
+/** Tests if a queue is empty.
+ * @param[in]	head	Head index
+ * @param[in]	tail	Tail index
+ */
+static inline int qempty(size_t head, size_t tail)
+{
+	return (head == tail);
+}
+
+#endif /* I__QUEUE_H__ */
--- a/src/include/rtt.h
+++ b/src/include/rtt.h
@ -0,0 +1,34 @@
+#ifndef RTT_H
+#define RTT_H
+#include <target.h>
+
+#define MAX_RTT_CHAN 16
+
+extern char rtt_ident[16];	    // string
+extern bool rtt_enabled;	    // rtt on/off
+extern bool rtt_found;              // control block found
+extern uint32_t rtt_cbaddr;         // control block address
+extern uint32_t rtt_min_poll_ms;    // min time between polls (ms)
+extern uint32_t rtt_max_poll_ms;    // max time between polls (ms)
+extern uint32_t rtt_max_poll_errs;  // max number of errors before disconnect
+extern bool rtt_auto_channel;       // manual or auto channel selection
+extern bool rtt_flag_skip;          // skip if host-to-target fifo full
+extern bool rtt_flag_block;         // block if host-to-target fifo full
+
+struct rtt_channel_struct {
+	bool is_enabled;            // does user want to see this channel?
+	bool is_configured;         // is channel configured in control block?
+	bool is_output;
+	uint32_t buf_addr;
+	uint32_t buf_size;
+	uint32_t head_addr;
+	uint32_t tail_addr;
+	uint32_t flag;
+};
+
+extern struct rtt_channel_struct rtt_channel[MAX_RTT_CHAN];
+
+// true if target memory access does not work when target running
+extern bool target_no_background_memory_access(target *cur_target);
+extern void poll_rtt(target *cur_target);
+#endif
--- a/src/include/rtt_if.h
+++ b/src/include/rtt_if.h
@ -0,0 +1,36 @@
+#ifndef RTT_IF_H
+#define RTT_IF_H
+/* rtt i/o to terminal */
+
+/* default buffer sizes, 8 bytes added to up buffer for alignment and padding */
+/* override RTT_UP_BUF_SIZE and RTT_DOWN_BUF_SIZE in platform.h if needed */
+
+#if !defined(RTT_UP_BUF_SIZE) || !defined(RTT_DOWN_BUF_SIZE)
+#if (PC_HOSTED == 1)
+#define RTT_UP_BUF_SIZE    (4096 + 8)
+#define RTT_DOWN_BUF_SIZE  (512)
+#elif defined(STM32F7)
+#define RTT_UP_BUF_SIZE    (4096 + 8)
+#define RTT_DOWN_BUF_SIZE  (2048)
+#elif defined(STM32F4)
+#define RTT_UP_BUF_SIZE    (2048 + 8)
+#define RTT_DOWN_BUF_SIZE  (256)
+#else /* stm32f103 */
+#define RTT_UP_BUF_SIZE    (1024 + 8)
+#define RTT_DOWN_BUF_SIZE  (256)
+#endif
+#endif
+
+/* hosted initialisation */
+extern int rtt_if_init(void);
+/* hosted teardown */
+extern int rtt_if_exit(void);
+
+/* target to host: write len bytes from the buffer starting at buf. return number bytes written */
+extern uint32_t rtt_write(const char *buf, uint32_t len);
+/* host to target: read one character, non-blocking. return character, -1 if no character */
+extern int32_t rtt_getchar();
+/* host to target: true if no characters available for reading */
+extern bool rtt_nodata();
+
+#endif
--- a/src/platforms/common/cdcacm.c
+++ b/src/platforms/common/cdcacm.c
@ -78,7 +78,7 @@ static const struct usb_device_descriptor dev_desc = {
 	.bDeviceClass = 0xEF,		/* Miscellaneous Device */
 	.bDeviceSubClass = 2,		/* Common Class */
 	.bDeviceProtocol = 1,		/* Interface Association */
-#ifdef LM4F
+#if defined(SAMD21E17) || defined(LM4F)
 	.bMaxPacketSize0 = 64,		/*Fixed for icdi*/
 #else
 	.bMaxPacketSize0 = 32,
@ -435,6 +435,8 @@ static void dfu_detach_complete(usbd_device *dev, struct usb_setup_data *req)
 	/* Reset core to enter bootloader */
 #if defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7EM__)
 	scb_reset_core();
+#else
+	scb_reset_system();
 #endif
 }

@ -524,7 +526,7 @@ static void cdcacm_set_config(usbd_device *dev, uint16_t wValue)
 	configured = wValue;

 	/* GDB interface */
-#if defined(STM32F4) || defined(LM4F)
+#if defined(STM32F4) || defined(LM4F) || defined(SAMD)
 	usbd_ep_setup(dev, CDCACM_GDB_ENDPOINT, USB_ENDPOINT_ATTR_BULK,
 	              CDCACM_PACKET_SIZE, gdb_usb_out_cb);
 #else
@ -580,6 +582,7 @@ void cdcacm_init(void)

 	nvic_set_priority(USB_IRQ, IRQ_PRI_USB);
 	nvic_enable_irq(USB_IRQ);
+	usbd_disconnect(usbdev, false);
 }

 void USB_ISR(void)
--- a/src/platforms/hosted/platform.c
+++ b/src/platforms/hosted/platform.c
@ -30,6 +30,10 @@
 #include "gdb_if.h"
 #include <signal.h>

+#ifdef ENABLE_RTT
+#include "rtt_if.h"
+#endif
+
 #include "bmp_remote.h"
 #include "bmp_hosted.h"
 #include "stlinkv2.h"
@ -58,6 +62,9 @@ static void exit_function(void)
 	default:
 		break;
 	}
+	#ifdef ENABLE_RTT
+	rtt_if_exit();
+	#endif
 	fflush(stdout);
 }

@ -110,6 +117,9 @@ void platform_init(int argc, char **argv)
 		exit(cl_execute(&cl_opts));
 	else {
 		gdb_if_init();
+		#ifdef ENABLE_RTT
+		rtt_if_init();
+		#endif
 		return;
 	}
 }
--- a/src/platforms/hosted/rtt_if.c
+++ b/src/platforms/hosted/rtt_if.c
@ -0,0 +1,127 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <general.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <rtt_if.h>
+
+/* maybe rewrite this as tcp server */
+
+#ifndef WIN32
+#include <termios.h>
+
+/* linux */
+static struct termios saved_ttystate;
+static bool tty_saved = false;
+
+/* set up and tear down */
+
+int rtt_if_init()
+{
+	struct termios ttystate;
+	tcgetattr(STDIN_FILENO, &saved_ttystate);
+	tty_saved = true;
+	tcgetattr(STDIN_FILENO, &ttystate);
+	ttystate.c_lflag &= ~ICANON;
+	ttystate.c_lflag &= ~ECHO;
+	ttystate.c_cc[VMIN] = 1;
+	tcsetattr(STDIN_FILENO, TCSANOW, &ttystate);
+	int flags = fcntl(0, F_GETFL, 0);
+	fcntl(0, F_SETFL, flags | O_NONBLOCK);
+	return 0;
+}
+
+int rtt_if_exit()
+{
+	if (tty_saved)
+		tcsetattr(STDIN_FILENO, TCSANOW, &saved_ttystate);
+	return 0;
+}
+
+/* write buffer to terminal */
+
+uint32_t rtt_write(const char *buf, uint32_t len)
+{
+	write(1, buf, len);
+	return len;
+}
+
+/* read character from terminal */
+
+int32_t rtt_getchar()
+{
+	char ch;
+	int len;
+	len = read(0, &ch, 1);
+	if (len == 1) return ch;
+	return -1;
+}
+
+/* true if no characters available */
+
+bool rtt_nodata()
+{
+	return false;
+}
+
+#else
+
+/* windows, output only */
+
+int rtt_if_init()
+{
+	return 0;
+}
+
+int rtt_if_exit()
+{
+	return 0;
+}
+
+/* write buffer to terminal */
+
+uint32_t rtt_write(const char *buf, uint32_t len)
+{
+	write(1, buf, len);
+	return len;
+}
+
+/* read character from terminal */
+
+int32_t rtt_getchar()
+{
+	return -1;
+}
+
+/* true if no characters available */
+
+bool rtt_nodata()
+{
+	return false;
+}
+
+#endif
--- a/src/platforms/jeff/Makefile.inc
+++ b/src/platforms/jeff/Makefile.inc
@ -0,0 +1,61 @@
+CROSS_COMPILE ?= arm-none-eabi-
+CC = $(CROSS_COMPILE)gcc
+OBJCOPY = $(CROSS_COMPILE)objcopy
+
+OPT_FLAGS := -Os
+
+ifeq ($(ENABLE_DEBUG), 1)
+CFLAGS += -DDEBUG_ME
+CFLAGS += -DENABLE_DEBUG
+endif
+
+ifeq ($(CUSTOM_SER), 1)
+CFLAGS += -DCUSTOM_SER
+endif
+
+ifeq ($(CONSOLE_NO_AUTO_CRLF), 1)
+CFLAGS += -DCONSOLE_NO_AUTO_CRLF
+endif
+
+ifeq ($(ENABLE_DEBUG), 1)
+CFLAGS += -g3 -ggdb
+endif
+
+CFLAGS += -mthumb -mcpu=cortex-m0plus -DDFU_SERIAL_LENGTH=9 \
+	-DSAMD -DSAMD21E17 -DBLACKMAGIC -I../libopencm3/include \
+	-Iplatforms/samd -msoft-float -ffunction-sections -fdata-sections -MD
+
+LINKER_SCRIPT="platforms/samd/samd.ld"
+LDFLAGS = -mthumb -mcpu=cortex-m0plus -msoft-float -nostartfiles -lc \
+	$(CPU_FLAGS) -T$(LINKER_SCRIPT) -Wl,--gc-sections \
+	-L../libopencm3/lib -lopencm3_samd -lnosys -lm -lgcc
+
+ifeq ($(ENABLE_DEBUG), 1)
+LDFLAGS += --specs=rdimon.specs
+else
+LDFLAGS += --specs=nano.specs
+endif
+
+VPATH += platforms/samd
+
+SRC +=	cdcacm.c	\
+	timing.c        \
+	traceswo.o      \
+	usbuart.c       \
+
+all:	blackmagic_full.bin blackmagic.bin blackmagic_dfu.bin blackmagic_dfu.hex
+
+blackmagic_dfu.bin : OBJCOPY_FLAGS := --pad-to 0x00002000 --gap-fill 0xFF -j .text -j .data
+blackmagic_dfu.bin : LINKER_SCRIPT := "platforms/samd/samd_boot.ld"
+
+blackmagic_dfu.elf: usbdfu.o
+	@echo "  LD      $@"
+	$(Q)$(CC) $^ -o $@ $(LDFLAGS)
+
+blackmagic_full.bin: blackmagic_dfu.bin blackmagic.bin
+	@echo "  CAT     $@"
+	$(Q)cp blackmagic.bin jeff-$(shell git describe --tags --always --dirty).bin
+	$(Q)cat $^ > $@
+
+host_clean:
+	$(Q)$(RM) -f blackmagic.bin blackmagic_full.bin blackmagic_dfu blackmagic_dfu.bin blackmagic_dfu.hex jeff*.bin
--- a/src/platforms/jeff/platform.c
+++ b/src/platforms/jeff/platform.c
@ -0,0 +1,346 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2018  Flirc Inc.
+ * Written by Jason Kotzin <jasonkotzin@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "general.h"
+#include "gdb_if.h"
+#include "cdcacm.h"
+#include "usbuart.h"
+#include "gdb_packet.h"
+
+#include <libopencm3/sam/d/nvic.h>
+#include <libopencm3/sam/d/port.h>
+#include <libopencm3/sam/d/gclk.h>
+#include <libopencm3/sam/d/pm.h>
+#include <libopencm3/sam/d/uart.h>
+#include <libopencm3/sam/d/adc.h>
+
+#include <libopencm3/cm3/systick.h>
+#include <libopencm3/cm3/scb.h>
+
+#include <libopencm3/sam/d/tc.h>
+#include <libopencm3/sam/d/eic.h>
+
+static struct gclk_hw clock = {
+	.gclk0 = SRC_DFLL48M,
+	.gclk1 = SRC_OSC8M,
+	.gclk1_div = 30,      /* divide clock for ADC  */
+	.gclk2 = SRC_OSC8M,
+	.gclk2_div = 100,     /* divide clock for TC */
+	.gclk3 = SRC_DFLL48M,
+	.gclk4 = SRC_DFLL48M,
+	.gclk5 = SRC_DFLL48M,
+	.gclk6 = SRC_DFLL48M,
+	.gclk7 = SRC_DFLL48M,
+};
+
+extern void trace_tick(void);
+
+uint8_t running_status;
+static volatile uint32_t time_ms;
+
+uint8_t button_pressed;
+
+uint8_t tpwr_enabled;
+
+void sys_tick_handler(void)
+{
+	if(running_status)
+		gpio_toggle(LED_PORT, LED_IDLE_RUN);
+
+	time_ms += 10;
+
+	uart_pop();
+}
+
+uint32_t platform_time_ms(void)
+{
+	return time_ms;
+}
+
+static void usb_setup(void)
+{
+	/* Enable USB */
+	INSERTBF(PM_APBBMASK_USB, 1, PM->apbbmask);
+
+	/* enable clocking to usb */
+	set_periph_clk(GCLK0, GCLK_ID_USB);
+	periph_clk_en(GCLK_ID_USB, 1);
+
+	gpio_config_special(PORTA, GPIO24, SOC_GPIO_PERIPH_G);
+	gpio_config_special(PORTA, GPIO25, SOC_GPIO_PERIPH_G);
+
+}
+
+static uint32_t timing_init(void)
+{
+	uint32_t cal = 0;
+
+	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
+	systick_set_reload(4800);	/* Interrupt us at 10 Hz */
+	systick_interrupt_enable();
+
+	systick_counter_enable();
+	return cal;
+}
+
+static void adc_init(void)
+{
+	gpio_config_special(ADC_PORT, ADC_POS_PIN, SOC_GPIO_PERIPH_B); /* +input */
+	gpio_config_special(ADC_PORT, ADC_REF_PIN, SOC_GPIO_PERIPH_B); /* reference */
+
+	set_periph_clk(GCLK1, GCLK_ID_ADC);
+	periph_clk_en(GCLK_ID_ADC, 1);
+
+	adc_enable(ADC_REFCTRL_VREFA,0,ADC_INPUTCTRL_GND,ADC_MUXPOS);
+}
+
+static void counter_init(void)
+{
+	/* enable bus and clock */
+	INSERTBF(PM_APBCMASK_TC3, 1, PM->apbcmask);
+
+	set_periph_clk(GCLK2, GCLK_ID_TC3);
+	periph_clk_en(GCLK_ID_TC3, 1);
+
+	/* reset */
+	tc_reset(3);
+
+	/* set CTRLA.PRESCALER and CTRLA.PRESYNC */
+	tc_config_ctrla(3,1,(7<<8));
+
+	/* set CC0 (approx. 5 seconds delay) */
+	tc_set_cc(3,0,1000);
+
+	/* enable MC0 interrupt */
+	tc_enable_interrupt(3,(1<<4));
+	nvic_enable_irq(NVIC_TC3_IRQ);
+}
+
+static void button_init(void)
+{
+	gpio_config_special(BUTTON_PORT, BUTTON_PIN, SOC_GPIO_PERIPH_A);
+
+	/* enable bus and clock */
+	INSERTBF(PM_APBAMASK_EIC, 1, PM->apbamask);
+
+	set_periph_clk(GCLK0, GCLK_ID_EIC);
+	periph_clk_en(GCLK_ID_EIC, 1);
+
+	/* configure r/f edge, enable filtering */
+	eic_set_config(15, 1, EIC_FALL);
+
+	/* enable the IEC */
+	eic_enable(1);
+
+	/* enable interrupts */
+	eic_enable_interrupt((1<<15));
+	nvic_enable_irq(NVIC_EIC_IRQ);
+}
+
+void platform_init(void)
+{
+	gclk_init(&clock);
+
+	usb_setup();
+
+	gpio_config_output(LED_PORT, LED_IDLE_RUN, 0);
+	gpio_config_output(TMS_PORT, TMS_PIN, 0);
+	gpio_config_output(TCK_PORT, TCK_PIN, 0);
+	gpio_config_output(TDI_PORT, TDI_PIN, 0);
+
+	gpio_config_output(TMS_PORT, TMS_DIR_PIN, 0);
+	gpio_set(TMS_PORT, TMS_DIR_PIN);
+
+	/* enable both input and output with pullup disabled by default */
+	PORT_DIRSET(SWDIO_PORT) = SWDIO_PIN;
+	PORT_PINCFG(SWDIO_PORT, SWDIO_PIN_NUM) |= GPIO_PINCFG_INEN | GPIO_PINCFG_PULLEN;
+	gpio_clear(SWDIO_PORT, SWDIO_PIN);
+
+	/* configure swclk_pin as output */
+	gpio_config_output(SWCLK_PORT, SWCLK_PIN, 0);
+	gpio_clear(SWCLK_PORT, SWCLK_PIN);
+
+	gpio_config_input(TDO_PORT, TDO_PIN, 0);
+	gpio_config_output(SRST_PORT, SRST_PIN, GPIO_OUT_FLAG_DEFAULT_HIGH);
+	gpio_clear(SRST_PORT, SRST_PIN);
+
+	/* setup uart led, disable by default*/
+	gpio_config_output(LED_PORT_UART, LED_UART, 0);//GPIO_OUT_FLAG_DEFAULT_HIGH);
+	gpio_clear(LED_PORT_UART, LED_UART);
+
+	/* set up TPWR */
+	gpio_set(PWR_BR_PORT, PWR_BR_PIN);
+	gpio_config_output(PWR_BR_PORT, PWR_BR_PIN, GPIO_OUT_FLAG_DEFAULT_HIGH);
+
+	timing_init();
+	usbuart_init();
+	cdcacm_init();
+	adc_init();
+	counter_init();
+	button_init();
+}
+
+uint8_t srst_state;
+void platform_srst_set_val(bool assert)
+{
+	volatile int i;
+	if (!assert) {
+		gpio_clear(SRST_PORT, SRST_PIN);
+		for(i = 0; i < 10000; i++) asm("nop");
+		srst_state = 0;
+	} else {
+		gpio_set(SRST_PORT, SRST_PIN);
+		srst_state = 1;
+	}
+}
+
+bool platform_srst_get_val(void)
+{
+	//return gpio_get(SRST_PORT, SRST_PIN) != 0;
+	return srst_state;
+}
+
+bool platform_target_get_power(void)
+{
+	//return !gpio_get(PWR_BR_PORT, PWR_BR_PIN);
+	return tpwr_enabled;
+}
+
+void platform_target_set_power(bool power)
+{
+	gpio_set_val(PWR_BR_PORT, PWR_BR_PIN, !power);
+	tpwr_enabled = power;
+}
+
+void platform_delay(uint32_t ms)
+{
+	platform_timeout timeout;
+	platform_timeout_set(&timeout, ms);
+	while (!platform_timeout_is_expired(&timeout));
+}
+
+uint32_t platform_target_voltage_sense(void)
+{
+	uint32_t val;
+	adc_start();
+
+	while (!(1&(ADC->intflag)));
+	val = ((485*adc_result())>>12); /* 330 without divider, 485 with it */
+	return val;
+}
+
+const char *platform_target_voltage(void)
+{
+	uint32_t voltage;
+	static char out[] = "0.0V";
+
+	adc_start();
+
+	voltage = platform_target_voltage_sense();
+
+	out[0] = '0' + (char)(voltage/100);
+	out[2] = '0' + (char)((voltage/10) % 10);
+
+	return out;
+}
+
+char *serial_no_read(char *s)
+{
+#ifdef CUSTOM_SER
+	s[0] = 'J';
+	s[1] = 'E';
+	s[2] = 'F';
+	s[3] = 'F';
+	return s;
+#else
+        int i;
+
+	volatile uint32_t unique_id = *(volatile uint32_t *)0x0080A00C +
+		*(volatile uint32_t *)0x0080A040 +
+		*(volatile uint32_t *)0x0080A044 +
+		*(volatile uint32_t *)0x0080A048;
+	
+        /* Fetch serial number from chip's unique ID */
+        for(i = 0; i < 8; i++) {
+                s[7-i] = ((unique_id >> (4*i)) & 0xF) + '0';
+        }
+
+        for(i = 0; i < 8; i++)
+                if(s[i] > '9')
+                        s[i] += 'A' - '9' - 1;
+	s[8] = 0;
+
+	return s;
+#endif
+}
+
+void print_serial(void)
+{
+	gdb_outf("0x%08X%08X%08X%08X\n", *(volatile uint32_t *)0x0080A048,
+			*(volatile uint32_t *)0x0080A044,
+			*(volatile uint32_t *)0x0080A040,
+			*(volatile uint32_t *)0x0080A00C);
+}
+
+void platform_request_boot(void)
+{
+}
+
+void eic_isr(void)
+{
+	if (!button_pressed){
+		/* set to rising-edge detection */
+		eic_set_config(15, 1, EIC_RISE);
+		
+		/* enable counter */
+		tc_enable(3,1);
+
+		button_pressed = 1;
+	} else {
+		/* set to falling-edge detection */
+		eic_set_config(15, 1, EIC_FALL);
+
+		/* disable and reset counter */
+		tc_enable(3,0);
+
+		button_pressed = 0;
+	}
+
+	/* clear the interrupt */
+	eic_clr_interrupt((1<<15));
+}
+
+void tc3_isr(void)
+{
+	if (tc_interrupt_flag(3) & 16)
+		scb_reset_system();
+}
+
+uint32_t swd_delay_cnt = 0;
+
+void platform_max_frequency_set(uint32_t freq)
+{
+	(void)freq;
+}
+
+uint32_t platform_max_frequency_get(void)
+{
+	return 0;
+}
--- a/src/platforms/jeff/platform.h
+++ b/src/platforms/jeff/platform.h
@ -0,0 +1,227 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2018  Flirc Inc.
+ * Written by Jason Kotzin <jasonkotzin@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __PLATFORM_H
+#define __PLATFORM_H
+
+#include <libopencm3/sam/d/port.h>
+#include <libopencm3/usb/usbd.h>
+#include <libopencm3/cm3/scb.h>
+#include <libopencm3/sam/d/nvmctrl.h>
+
+#include "timing.h"
+#include "version.h"
+
+//#define PLATFORM_HAS_DEBUG
+//#define USBUART_DEBUG
+#define PLATFORM_HAS_UART_WHEN_SWDP
+#define PLATFORM_HAS_POWER_SWITCH
+#define PLATFORM_HAS_BOOTLOADER
+#define PLATFORM_HAS_PRINTSERIAL
+
+//#define BOARD_IDENT             "Black Magic Probe (SAMD), (Firmware " FIRMWARE_VERSION ")"
+#define BOARD_IDENT_DFU		"Black Magic (Upgrade) for Launchpad, (Firmware " FIRMWARE_VERSION ")"
+//#define DFU_IDENT               "Black Magic Firmware Upgrade (SAMD)"
+#define DFU_IFACE_STRING	"hid"
+
+#define BOARD_IDENT_UPD       "Black Magic (DFU Upgrade), SAMD21, (Firmware " FIRMWARE_VERSION ")"
+#define UPD_IFACE_STRING       "@Internal Flash   /0x00000000/1*008Ka,15*8Kg"
+
+#define PLATFORM_IDENT          " "
+
+extern uint8_t running_status;
+extern uint32_t swd_delay_cnt;
+
+#ifdef DEBUG_ME
+
+#define LED_PORT	PORTA
+#define LED_IDLE_RUN	GPIO11
+#define LED_ERROR	GPIO10
+
+#define TMS_PORT	PORTA
+#define TMS_PIN		GPIO1
+#define TMS_DIR_PIN	GPIO5
+
+#define TCK_PORT	PORTA
+#define TCK_PIN		GPIO2
+
+#define TDI_PORT	PORTA
+#define TDI_PIN		GPIO16
+
+#define TDO_PORT	PORTA
+#define TDO_PIN		GPIO19
+
+#define SWO_PORT	PORTA
+#define SWO_PIN		GPIO6
+
+#define SWDIO_PORT	PORTA
+#define SWDIO_PIN	TMS_PIN
+#define SWDIO_PIN_NUM	1
+
+#define SWCLK_PORT	PORTA
+#define SWCLK_PIN	TCK_PIN
+
+#define SRST_PORT	PORTA
+#define SRST_PIN	GPIO7
+
+#define LED_PORT_UART	PORTA
+#define LED_UART	GPIO12
+
+#define UART_TX_PIN	GPIO8
+#define UART_RX_PIN	GPIO9
+#define UART_PERIPH	SOC_GPIO_PERIPH_C
+#define UART_PERIPH_2	SOC_GPIO_PERIPH_C
+
+#define ADC_PORT	PORTA
+#define ADC_REF_PIN	GPIO3
+#define ADC_POS_PIN	GPIO4
+#define ADC_MUXPOS	4
+
+#define BUTTON_PORT	PORTA
+#define BUTTON_PIN	GPIO27
+
+#else
+
+/* Hardware definitions... */
+#define JTAG_PORT 	PORTA
+#define TDI_PORT	JTAG_PORT
+#define TMS_DIR_PORT	JTAG_PORT
+#define TMS_PORT	JTAG_PORT
+#define TCK_PORT	JTAG_PORT
+#define TDO_PORT	JTAG_PORT
+#define TMS_DIR_PIN	GPIO15
+#define TMS_PIN		GPIO0
+#define TCK_PIN		GPIO6
+#define TDI_PIN		GPIO16
+#define TDO_PIN		GPIO19
+
+#define SWDIO_DIR_PORT	JTAG_PORT
+#define SWDIO_PORT 	JTAG_PORT
+#define SWCLK_PORT 	JTAG_PORT
+#define SWDIO_DIR_PIN	TMS_DIR_PIN
+#define SWDIO_PIN	TMS_PIN
+#define SWDIO_PIN_NUM	0
+#define SWCLK_PIN	TCK_PIN
+
+#define TRST_PORT	PORTA
+#define TRST_PIN	GPIO27
+#define PWR_BR_PORT	PORTA
+#define PWR_BR_PIN	GPIO28
+#define SRST_PORT	PORTA
+#define SRST_PIN	GPIO8
+#define SRST_SENSE_PORT	GPIOA
+#define SRST_SENSE_PIN	GPIO9
+#define TRGT_SENSE	GPIO2
+
+#define LED_PORT	PORTA
+#define LED_PORT_UART	PORTA
+#define LED_0		GPIO10
+#define LED_1		GPIO11
+#define LED_2		GPIO14
+//#define LED_2		GPIO13
+#define LED_UART	LED_1	/* Orange */
+#define LED_IDLE_RUN	LED_0	/* Yellow */
+#define LED_ERROR	LED_2	/* Red */
+
+#define UART_TX_PIN	GPIO4
+#define UART_RX_PIN	GPIO7
+#define UART_PERIPH	SOC_GPIO_PERIPH_D
+#define UART_PERIPH_2	SOC_GPIO_PERIPH_C
+
+#define SWO_PORT	JTAG_PORT
+#define SWO_PIN		SWD_PIN
+
+#define ADC_PORT	PORTA
+#define ADC_REF_PIN	GPIO3
+#define ADC_POS_PIN	GPIO2
+#define ADC_MUXPOS	0
+
+#define BUTTON_PORT	PORTA
+#define BUTTON_PIN	GPIO27
+
+#endif
+
+#define TMS_SET_MODE()	{ \
+	gpio_config_output(TMS_PORT, TMS_PIN, 0); \
+	gpio_set(TMS_PORT, TMS_DIR_PIN); \
+}
+
+#define SWDIO_MODE_FLOAT() do { \
+	PORT_DIRCLR(SWDIO_PORT) = SWDIO_PIN; \
+	gpio_set(SWDIO_PORT, SWDIO_PIN); \
+	gpio_clear(TMS_PORT, TMS_DIR_PIN); \
+} while(0)
+#define SWDIO_MODE_DRIVE() do { \
+	PORT_DIRSET(SWDIO_PORT) = SWDIO_PIN; \
+	gpio_set(TMS_PORT, TMS_DIR_PIN); \
+} while(0)
+
+/* extern usbd_driver samd21_usb_driver; */
+#define USB_DRIVER	samd21_usb_driver
+#define USB_IRQ		NVIC_USB_IRQ
+#define USB_ISR		usb_isr
+
+#define IRQ_PRI_USB	(2 << 4)
+
+#define INLINE_GPIO
+
+#define gpio_set_val(port, pin, val) do {	\
+	if(val)					\
+		_gpio_set((port), (pin));	\
+	else					\
+		_gpio_clear((port), (pin));	\
+} while(0)
+
+#ifdef INLINE_GPIO
+static inline void _gpio_set(uint32_t gpioport, uint32_t gpios)
+{
+	PORT_OUTSET(gpioport) = gpios;
+}
+#define gpio_set _gpio_set
+
+static inline void _gpio_clear(uint32_t gpioport, uint32_t gpios)
+{
+	PORT_OUTCLR(gpioport) = gpios;
+}
+#define gpio_clear _gpio_clear
+
+static inline uint16_t _gpio_get(uint32_t gpioport, uint32_t gpios)
+{
+	return (uint32_t)PORT_IN(gpioport) & gpios;
+}
+#define gpio_get _gpio_get
+#endif
+
+#define DEBUG(...)
+
+#define SET_RUN_STATE(state)	{running_status = (state);}
+#define SET_IDLE_STATE(state)	{gpio_set_val(LED_PORT, LED_IDLE_RUN, state);}
+#define SET_ERROR_STATE(state)	{gpio_set_val(LED_PORT, LED_ERROR, state);}
+
+static inline int platform_hwversion(void)
+{
+	        return 0;
+}
+
+void uart_pop(void);
+int usbuart_convert_tdio(uint32_t arg);
+int usbuart_convert_tdio_enabled(void);
+void print_serial(void);
+#endif
--- a/src/platforms/jeff/usbdfu.c
+++ b/src/platforms/jeff/usbdfu.c
@ -0,0 +1,351 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2010 Gareth McMullin <gareth@blacksphere.co.nz>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include <libopencm3/sam/d/gclk.h>
+#include <libopencm3/sam/d/port.h>
+#include <libopencm3/sam/d/nvmctrl.h>
+#include <libopencm3/cm3/scb.h>
+#include <libopencm3/usb/usbd.h>
+#include <libopencm3/usb/dfu.h>
+
+#include <libopencm3/sam/d/nvic.h>
+#include <libopencm3/sam/d/pm.h>
+#include <libopencm3/sam/d/bitfield.h>
+#include <libopencm3/sam/d/usb.h>
+
+//#define APP_ADDRESS	0x08002000
+//#define APP_ADDRESS	0x00002000
+#define APP_ADDRESS	0x00002000
+//#define APP_ADDRESS	0x00004000
+
+/* Commands sent with wBlockNum == 0 as per ST implementation. */
+#define CMD_SETADDR	0x21
+#define CMD_ERASE	0x41
+
+#define BUTTON_PORT PORTA
+#define BUTTON_PIN GPIO27
+
+#define BUF_SIZE 4096
+
+static struct gclk_hw clock = {
+        .gclk0 = SRC_DFLL48M,
+        .gclk1 = SRC_OSC8M,
+        /* clock 1 has 8 divider, clock should be over 1khz for 1ms timer */
+        .gclk1_div = 100,
+        .gclk2 = SRC_DFLL48M,
+        .gclk3 = SRC_DFLL48M,
+        .gclk3_div = 1,
+        .gclk4 = SRC_OSC8M,
+        .gclk4_div = 1,
+        .gclk5 = SRC_DFLL48M,
+        .gclk6 = SRC_DFLL48M,
+        .gclk7 = SRC_DFLL48M,
+};
+
+/* We need a special large control buffer for this device: */
+uint8_t usbd_control_buffer[BUF_SIZE];
+
+static enum dfu_state usbdfu_state = STATE_DFU_IDLE;
+
+static struct {
+	uint8_t buf[sizeof(usbd_control_buffer)];
+	uint16_t len;
+	uint32_t addr;
+	uint16_t blocknum;
+} prog;
+
+const struct usb_device_descriptor dev = {
+	.bLength = USB_DT_DEVICE_SIZE,
+	.bDescriptorType = USB_DT_DEVICE,
+	.bcdUSB = 0x0200,
+	.bDeviceClass = 0,
+	.bDeviceSubClass = 0,
+	.bDeviceProtocol = 0,
+	.bMaxPacketSize0 = 64,
+	.idVendor = 0x1D50,
+	.idProduct = 0x6017,
+	.bcdDevice = 0x0200,
+	.iManufacturer = 1,
+	.iProduct = 2,
+	.iSerialNumber = 3,
+	.bNumConfigurations = 1,
+};
+
+const struct usb_dfu_descriptor dfu_function = {
+	.bLength = sizeof(struct usb_dfu_descriptor),
+	.bDescriptorType = DFU_FUNCTIONAL,
+	.bmAttributes = USB_DFU_CAN_DOWNLOAD | USB_DFU_WILL_DETACH,
+	.wDetachTimeout = 255,
+	.wTransferSize = BUF_SIZE,
+	.bcdDFUVersion = 0x011A,
+};
+
+const struct usb_interface_descriptor iface = {
+	.bLength = USB_DT_INTERFACE_SIZE,
+	.bDescriptorType = USB_DT_INTERFACE,
+	.bInterfaceNumber = 0,
+	.bAlternateSetting = 0,
+	.bNumEndpoints = 0,
+	.bInterfaceClass = 0xFE, /* Device Firmware Upgrade */
+	.bInterfaceSubClass = 1,
+	.bInterfaceProtocol = 2,
+
+	/* The ST Microelectronics DfuSe application needs this string.
+	 * The format isn't documented... */
+	.iInterface = 4,
+
+	.extra = &dfu_function,
+	.extralen = sizeof(dfu_function),
+};
+
+const struct usb_interface ifaces[] = {{
+	.num_altsetting = 1,
+	.altsetting = &iface,
+}};
+
+const struct usb_config_descriptor config = {
+	.bLength = USB_DT_CONFIGURATION_SIZE,
+	.bDescriptorType = USB_DT_CONFIGURATION,
+	.wTotalLength = 0,
+	.bNumInterfaces = 1,
+	.bConfigurationValue = 1,
+	.iConfiguration = 0,
+	.bmAttributes = 0xC0,
+	.bMaxPower = 0x32,
+
+	.interface = ifaces,
+};
+
+static const char *usb_strings[] = {
+	"Black Sphere Technologies",
+	"DFU Demo",
+	"DEMO",
+	/* This string is used by ST Microelectronics' DfuSe utility. */
+	//"@Internal Flash   /0x08000000/8*001Ka,56*001Kg",
+	"@Internal Flash   /0x00000000/1*008Ka,15*008Kg",
+	//"@Internal Flash   /0x00000000/1*0016Ka,15*0016Kg",
+};
+
+static uint8_t usbdfu_getstatus(uint32_t *bwPollTimeout)
+{
+	switch (usbdfu_state) {
+	case STATE_DFU_DNLOAD_SYNC:
+		usbdfu_state = STATE_DFU_DNBUSY;
+		*bwPollTimeout = 100;
+		return DFU_STATUS_OK;
+	case STATE_DFU_MANIFEST_SYNC:
+		/* Device will reset when read is complete. */
+		usbdfu_state = STATE_DFU_MANIFEST;
+		return DFU_STATUS_OK;
+	default:
+		return DFU_STATUS_OK;
+	}
+}
+
+static void usbdfu_getstatus_complete(usbd_device *usbd_dev, struct usb_setup_data *req)
+{
+	int i;
+	(void)req;
+	(void)usbd_dev;
+
+	switch (usbdfu_state) {
+	case STATE_DFU_DNBUSY:
+		//flash_unlock();
+		if (prog.blocknum == 0) {
+			switch (prog.buf[0]) {
+			case CMD_ERASE:
+				{
+					uint32_t *dat = (uint32_t *)(prog.buf + 1);
+					nvmctrl_erase_row(*dat); //flash_erase_page(*dat);
+				}
+				break;
+			case CMD_SETADDR:
+				{
+					uint32_t *dat = (uint32_t *)(prog.buf + 1);
+					prog.addr = *dat;
+				}
+				break;
+			}
+		} else {
+			//uint32_t baseaddr = prog.addr + ((prog.blocknum - 2) *
+			//	       dfu_function.wTransferSize);
+			uint32_t baseaddr = prog.addr;
+			//for (i = 0; i < prog.len; i += 2) {
+			        //uint16_t *dat = (uint16_t *)(prog.buf + i);
+				//flash_program_half_word(baseaddr + i,
+				//		*dat);
+			for (i = 0; i < BUF_SIZE; i += 256){
+				nvmctrl_erase_row(baseaddr+i);
+				nvmctrl_write_row(baseaddr+i, prog.buf+i);
+			}
+				//}
+		}
+		//flash_lock();
+
+		/* Jump straight to dfuDNLOAD-IDLE, skipping dfuDNLOAD-SYNC. */
+		usbdfu_state = STATE_DFU_DNLOAD_IDLE;
+		return;
+	case STATE_DFU_MANIFEST:
+		/* reset USB */
+		INSERTBF(USB_CTRLA_SWRST, 1, USB->ctrla);
+		/* jump to app */
+		if ((*(volatile uint32_t *)APP_ADDRESS & 0x2FFE0000) == 0x20000000) {
+
+			/* Set vector table base address. */
+			//SCB_VTOR = APP_ADDRESS & 0xFFFF;
+			SCB_VTOR = APP_ADDRESS;
+			/* Initialise master stack pointer. */
+			asm volatile("msr msp, %0"::"g"
+				     (*(volatile uint32_t *)APP_ADDRESS));
+			/* Jump to application. */
+			(*(void (**)())(APP_ADDRESS + 4))();
+		}
+
+		//scb_reset_system();
+		return; /* Will never return. */
+	default:
+		return;
+	}
+}
+
+static enum usbd_request_return_codes usbdfu_control_request(usbd_device *dev,
+		struct usb_setup_data *req, uint8_t **buf, uint16_t *len,
+		void (**complete)(usbd_device *dev, struct usb_setup_data *req))
+{
+	(void)dev;
+
+	if ((req->bmRequestType & 0x7F) != 0x21)
+		return 0; /* Only accept class request. */
+
+	switch (req->bRequest) {
+	case DFU_DNLOAD:
+		if ((len == NULL) || (*len == 0)) {
+			usbdfu_state = STATE_DFU_MANIFEST_SYNC;
+			return 1;
+		} else {
+			/* Copy download data for use on GET_STATUS. */
+			prog.blocknum = req->wValue;
+			prog.len = *len;
+			memcpy(prog.buf, *buf, *len);
+			usbdfu_state = STATE_DFU_DNLOAD_SYNC;
+			return 1;
+		}
+	case DFU_CLRSTATUS:
+		/* Clear error and return to dfuIDLE. */
+		if (usbdfu_state == STATE_DFU_ERROR)
+			usbdfu_state = STATE_DFU_IDLE;
+		return 1;
+	case DFU_ABORT:
+		/* Abort returns to dfuIDLE state. */
+		usbdfu_state = STATE_DFU_IDLE;
+		return 1;
+	case DFU_UPLOAD:
+		/* Upload not supported for now. */
+		return 0;
+	case DFU_GETSTATUS: {
+		uint32_t bwPollTimeout = 0; /* 24-bit integer in DFU class spec */
+		(*buf)[0] = usbdfu_getstatus(&bwPollTimeout);
+		(*buf)[1] = bwPollTimeout & 0xFF;
+		(*buf)[2] = (bwPollTimeout >> 8) & 0xFF;
+		(*buf)[3] = (bwPollTimeout >> 16) & 0xFF;
+		(*buf)[4] = usbdfu_state;
+		(*buf)[5] = 0; /* iString not used here */
+		*len = 6;
+		*complete = usbdfu_getstatus_complete;
+		return 1;
+		}
+	case DFU_GETSTATE:
+		/* Return state with no state transision. */
+		*buf[0] = usbdfu_state;
+		*len = 1;
+		return 1;
+	}
+
+	return 0;
+}
+
+static void usbdfu_set_config(usbd_device *usbd_dev, uint16_t wValue)
+{
+	(void)wValue;
+
+	usbd_register_control_callback(
+				usbd_dev,
+				USB_REQ_TYPE_CLASS | USB_REQ_TYPE_INTERFACE,
+				USB_REQ_TYPE_TYPE | USB_REQ_TYPE_RECIPIENT,
+				usbdfu_control_request);
+}
+
+static void usb_setup(void)
+{
+        /* Enable USB */
+        INSERTBF(PM_APBBMASK_USB, 1, PM->apbbmask);
+
+        /* enable clocking to usb */
+        set_periph_clk(GCLK0, GCLK_ID_USB);
+        periph_clk_en(GCLK_ID_USB, 1);
+
+        gpio_config_special(PORTA, GPIO24, SOC_GPIO_PERIPH_G);
+        gpio_config_special(PORTA, GPIO25, SOC_GPIO_PERIPH_G);
+
+}
+
+int main(void)
+{
+	usbd_device *usbd_dev;
+
+	gclk_init(&clock);
+	//rcc_periph_clock_enable(RCC_GPIOA);
+	//gpio_config_input(BUTTON_PORT,BUTTON_PIN,GPIO_IN_FLAG_PULLUP);
+	gpio_config_input(BUTTON_PORT,BUTTON_PIN,0);
+
+	nvmctrl_init(0,0);
+
+	usb_setup();
+
+	if (PM->rcause != (1<<6))
+	if (gpio_get(BUTTON_PORT, BUTTON_PIN)) {
+	//if (gpio_get(PORTA, GPIO27)) {
+		/* Boot the application if it's valid. */
+		if ((*(volatile uint32_t *)APP_ADDRESS & 0x2FFE0000) == 0x20000000) {
+
+			/* Set vector table base address. */
+			//SCB_VTOR = APP_ADDRESS & 0xFFFF;
+			SCB_VTOR = APP_ADDRESS;
+			/* Initialise master stack pointer. */
+			asm volatile("msr msp, %0"::"g"
+				     (*(volatile uint32_t *)APP_ADDRESS));
+			/* Jump to application. */
+			(*(void (**)())(APP_ADDRESS + 4))();
+		}
+	}
+
+	usbd_dev = usbd_init(&samd21_usb_driver, &dev, &config, usb_strings, 4, usbd_control_buffer, sizeof(usbd_control_buffer));
+	usbd_register_set_config_callback(usbd_dev, usbdfu_set_config);
+
+	//nvic_enable_irq(NVIC_USB_IRQ);
+
+        /* Connect USB cable */
+        usbd_disconnect(usbd_dev, false);
+
+	//gpio_clear(GPIOC, GPIO11);
+
+	while (1)
+		usbd_poll(usbd_dev);
+}
--- a/src/platforms/samd/gdb_if.c
+++ b/src/platforms/samd/gdb_if.c
@ -0,0 +1,103 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2011  Black Sphere Technologies Ltd.
+ * Written by Gareth McMullin <gareth@blacksphere.co.nz>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* This file implements a transparent channel over which the GDB Remote
+ * Serial Debugging protocol is implemented.  This implementation for STM32
+ * uses the USB CDC-ACM device bulk endpoints to implement the channel.
+ */
+
+#include "general.h"
+#include "gdb_if.h"
+#include "cdcacm.h"
+
+#include <libopencm3/usb/usbd.h>
+
+static volatile uint32_t head_out, tail_out;
+static volatile uint32_t count_in;
+static volatile uint8_t buffer_out[16*CDCACM_PACKET_SIZE];
+static volatile uint8_t buffer_in[CDCACM_PACKET_SIZE];
+
+void gdb_if_putchar(unsigned char c, int flush)
+{
+	buffer_in[count_in++] = c;
+	if(flush || (count_in == CDCACM_PACKET_SIZE)) {
+		/* Refuse to send if USB isn't configured, and
+		 * don't bother if nobody's listening */
+		if((cdcacm_get_config() != 1) || !cdcacm_get_dtr()) {
+			count_in = 0;
+			return;
+		}
+		while(usbd_ep_write_packet(usbdev, CDCACM_GDB_ENDPOINT,
+			(uint8_t *)buffer_in, count_in) <= 0);
+		count_in = 0;
+	}
+}
+
+void gdb_usb_out_cb(usbd_device *dev, uint8_t ep)
+{
+	(void)ep;
+	static uint8_t buf[CDCACM_PACKET_SIZE];
+
+	usbd_ep_nak_set(dev, CDCACM_GDB_ENDPOINT, 1);
+        uint32_t count = usbd_ep_read_packet(dev, CDCACM_GDB_ENDPOINT,
+                                        (uint8_t *)buf, CDCACM_PACKET_SIZE);
+
+
+	uint32_t idx;
+	for (idx=0; idx<count; idx++) {
+		buffer_out[head_out++ % sizeof(buffer_out)] = buf[idx];
+	}
+
+	usbd_ep_nak_set(dev, CDCACM_GDB_ENDPOINT, 0);
+}
+
+unsigned char gdb_if_getchar(void)
+{
+
+	while(tail_out == head_out) {
+		/* Detach if port closed */
+		if(!cdcacm_get_dtr())
+			return 0x04;
+
+		while(cdcacm_get_config() != 1);
+	}
+
+	return buffer_out[tail_out++ % sizeof(buffer_out)];
+}
+
+unsigned char gdb_if_getchar_to(int timeout)
+{
+	platform_timeout t;
+	platform_timeout_set(&t, timeout);
+
+	if(head_out == tail_out) do {
+		/* Detach if port closed */
+		if(!cdcacm_get_dtr())
+			return 0x04;
+
+		while(cdcacm_get_config() != 1);
+	} while(!platform_timeout_is_expired(&t) && head_out == tail_out);
+
+	if(head_out != tail_out)
+		return gdb_if_getchar();
+
+	return -1;
+}
+
--- a/src/platforms/samd/rtt_if.c
+++ b/src/platforms/samd/rtt_if.c
@ -0,0 +1,134 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "general.h"
+#include "platform.h"
+#include <assert.h>
+#include "cdcacm.h"
+#include "rtt.h"
+#include "rtt_if.h"
+
+/*********************************************************************
+*
+*       rtt terminal i/o
+*
+**********************************************************************
+*/
+
+/* usb uart receive buffer */
+static char recv_buf[RTT_DOWN_BUF_SIZE];
+static uint32_t recv_head = 0;
+static uint32_t recv_tail = 0;
+
+/* data from host to target: number of free bytes in usb receive buffer */
+inline static uint32_t recv_bytes_free()
+{
+	if (recv_tail <= recv_head)
+		return sizeof(recv_buf) - recv_head + recv_tail - 1;
+	else
+		return recv_tail - recv_head - 1;
+}
+
+/* data from host to target: true if not enough free buffer space and we need to close flow control */
+inline static bool recv_set_nak()
+{
+	assert(sizeof(recv_buf) > 2 * CDCACM_PACKET_SIZE);
+	return recv_bytes_free() < 2 * CDCACM_PACKET_SIZE;
+}
+
+/* usbuart_usb_out_cb is called when usb uart has received new data for target.
+   this routine has to be fast */
+
+void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
+{
+	(void)dev;
+	(void)ep;
+	char usb_buf[CDCACM_PACKET_SIZE];
+
+	/* close flow control while processing packet */
+	usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 1);
+
+	const uint16_t len = usbd_ep_read_packet(usbdev, CDCACM_UART_ENDPOINT, usb_buf, CDCACM_PACKET_SIZE);
+
+	/* skip flag: drop packet if not enough free buffer space */
+	if (rtt_flag_skip && len > recv_bytes_free()) {
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+		return;
+	}
+
+	/* copy data to recv_buf */
+	for (int i = 0; i < len; i++) {
+		uint32_t next_recv_head = (recv_head + 1) % sizeof(recv_buf);
+		if (next_recv_head == recv_tail)
+			break; /* overflow */
+		recv_buf[recv_head] = usb_buf[i];
+		recv_head = next_recv_head;
+	}
+
+	/* block flag: flow control closed if not enough free buffer space */
+	if (!(rtt_flag_block && recv_set_nak()))
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+
+	return;
+}
+
+/* rtt host to target: read one character */
+int32_t rtt_getchar()
+{
+	int retval;
+
+	if (recv_head == recv_tail)
+		return -1;
+	retval = recv_buf[recv_tail];
+	recv_tail = (recv_tail + 1) % sizeof(recv_buf);
+
+	/* open flow control if enough free buffer space */
+	if (!recv_set_nak())
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+
+	return retval;
+}
+
+/* rtt host to target: true if no characters available for reading */
+bool rtt_nodata()
+{
+	return recv_head == recv_tail;
+}
+
+/* rtt target to host: write string */
+uint32_t rtt_write(const char *buf, uint32_t len)
+{
+	if (len != 0 && usbdev && cdcacm_get_config() && cdcacm_get_dtr()) {
+		for (uint32_t p = 0; p < len; p += CDCACM_PACKET_SIZE) {
+			uint32_t plen = MIN(CDCACM_PACKET_SIZE, len - p);
+			while(usbd_ep_write_packet(usbdev, CDCACM_UART_ENDPOINT, buf + p, plen) <= 0);
+		}
+		/* flush 64-byte packet on full-speed */
+		if (CDCACM_PACKET_SIZE == 64 && (len % CDCACM_PACKET_SIZE) == 0)
+			while(usbd_ep_write_packet(usbdev, CDCACM_UART_ENDPOINT, NULL, 0) <= 0);
+	}
+	return len;
+}
--- a/src/platforms/samd/samd.ld
+++ b/src/platforms/samd/samd.ld
@ -0,0 +1,28 @@
+/*
+ * This file is part of the libopenstm32 project.
+ *
+ * Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Define memory regions. */
+MEMORY
+{
+	rom (rx) : ORIGIN = 0x00002000, LENGTH = 120K /* 128k - 8k for bootloader */
+	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 16K
+}
+
+/* Include the common ld script from libopenstm32. */
+INCLUDE cortex-m-generic.ld
--- a/src/platforms/samd/samd_boot.ld
+++ b/src/platforms/samd/samd_boot.ld
@ -0,0 +1,28 @@
+/*
+ * This file is part of the libopenstm32 project.
+ *
+ * Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Define memory regions. */
+MEMORY
+{
+	rom (rx) : ORIGIN = 0x00000000, LENGTH = 128K /* 128k - 8k for bootloader */
+	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 16K
+}
+
+/* Include the common ld script from libopenstm32. */
+INCLUDE cortex-m-generic.ld
--- a/src/platforms/samd/traceswo.c
+++ b/src/platforms/samd/traceswo.c
@ -0,0 +1,57 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2018  Flirc Inc.
+ * Written by Jason Kotzin <jasonkotzin@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* This file implements capture of the TRACESWO output.
+ *
+ * ARM DDI 0403D - ARMv7M Architecture Reference Manual
+ * ARM DDI 0337I - Cortex-M3 Technical Reference Manual
+ * ARM DDI 0314H - CoreSight Components Technical Reference Manual
+ */
+
+#include "general.h"
+#include "cdcacm.h"
+
+void traceswo_init(void)
+{
+}
+
+void traceswo_baud(unsigned int baud)
+{
+	baud++;
+}
+
+void trace_buf_push(void)
+{
+}
+
+void trace_buf_drain(usbd_device *dev, uint8_t ep)
+{
+	ep ++;
+	if (dev == NULL)
+		return;
+}
+
+void trace_tick(void)
+{
+}
+
+void TRACEUART_ISR(void)
+{
+}
--- a/src/platforms/samd/usbuart.c
+++ b/src/platforms/samd/usbuart.c
@ -0,0 +1,251 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2018  Flirc Inc.
+ * Written by Jason Kotzin <jasonkotzin@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "general.h"
+#include "cdcacm.h"
+
+#include <libopencm3/sam/d/bitfield.h>
+#include <libopencm3/sam/d/gclk.h>
+#include <libopencm3/sam/d/pm.h>
+#include <libopencm3/sam/d/port.h>
+#include <libopencm3/sam/d/nvic.h>
+#include <libopencm3/sam/d/uart.h>
+
+#include <libopencm3/cm3/cortex.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/cm3/scb.h>
+#include <libopencm3/cm3/scs.h>
+#include <libopencm3/cm3/systick.h>
+
+#include <libopencm3/usb/usbd.h>
+#include <libopencm3/usb/cdc.h>
+
+#include "queue.h"
+
+#define Q_SIZE		1024
+
+/* Active USART number */
+static uint8_t USART_NUM = 0;
+
+/* Current Baud Rate setting */
+static uint32_t current_baud = 115200;
+
+usbd_device * usbdev;
+
+/* input and output ring buffer */
+struct {
+        char buf[Q_SIZE];
+        volatile size_t head, tail;
+} rx, tx;
+
+#ifndef ENABLE_RTT
+/* non blocking putc function */
+static void usart_putc(char c)
+{
+#ifdef CONSOLE_NO_AUTO_CRLF
+	if (c == '\n')
+		usart_putc('\r');
+#endif
+
+	if (qfull(tx.head, tx.tail, Q_SIZE))
+		return;
+
+	cm_disable_interrupts();
+	tx.buf[tx.head] = c;
+	tx.head = qinc(tx.head, Q_SIZE);
+	cm_enable_interrupts();
+
+	/* kick the transmitter to restart interrupts */
+	usart_enable_tx_interrupt(USART_NUM);
+}
+#endif
+
+void usbuart_init(void)
+{
+	/* enable gpios */
+	gpio_config_special(PORTA, UART_TX_PIN, UART_PERIPH); /* tx pin */
+	gpio_config_special(PORTA, UART_RX_PIN, UART_PERIPH); /* rx pin */
+
+	/* enable clocking to sercom0 */
+	set_periph_clk(GCLK0, GCLK_ID_SERCOM0_CORE);
+	periph_clk_en(GCLK_ID_SERCOM0_CORE, 1);
+
+	//usart_enable(USART_NUM, current_baud);
+	usart_setup(USART_NUM, current_baud);
+#ifndef DEBUG_ME
+        usart_set_pads(USART_NUM, 3, 0); /* bm-sam uses different pads */
+#endif
+	usart_enable(USART_NUM, 0); /* baud==0 so setup is skipped */
+
+	usart_enable_rx_interrupt(USART_NUM);
+	usart_enable_tx_interrupt(USART_NUM);
+}
+
+static uint8_t convert_tdio_enabled;
+int usbuart_convert_tdio(uint32_t arg)
+{
+
+	(void) arg;
+
+	convert_tdio_enabled = arg;
+
+	if (!convert_tdio_enabled) {
+		usart_disable(1);
+		USART_NUM = 0;
+		usbuart_init();
+		return current_baud;
+	}
+
+        gpio_config_special(PORTA, TDI_PIN, UART_PERIPH_2); /* TX */
+	gpio_config_special(PORTA, TDO_PIN, UART_PERIPH_2); /* RX */
+
+        /* disable USART0 (we will be using USART1 now) */
+        usart_disable(0);
+
+	USART_NUM = 1;
+
+        /* Select and Enable system clock */
+	set_periph_clk(GCLK0, GCLK_ID_SERCOM1_CORE);
+        periph_clk_en(GCLK_ID_SERCOM1_CORE, 1);
+
+	usart_setup(1, current_baud);
+        usart_set_pads(1, 3, 0); /* uses different pads than the default */
+	usart_enable(1, 0); /* baud==0 so setup is skipped */
+
+        usart_enable_rx_interrupt(1);
+        usart_enable_tx_interrupt(1);
+
+	return current_baud;
+
+}
+
+int usbuart_convert_tdio_enabled(void)
+{
+	return convert_tdio_enabled;
+}
+
+void usbuart_set_line_coding(struct usb_cdc_line_coding *coding)
+{
+	uint8_t sbmode = (coding->bCharFormat == 2) ? 1 : 0;
+	uint8_t parity = (coding->bParityType == 1) ? 0 : 1;
+	uint8_t form   = (coding->bParityType) ? 1 : 0;
+	uint8_t chsize = (form) ? coding->bDataBits + 1 : coding->bDataBits;
+
+	usart_disable(USART_NUM);
+
+	/* set baud rate */
+	usart_set_baudrate(USART_NUM, coding->dwDTERate);
+
+	/* set data size, stop mode, and parity */
+	usart_set_chsize(USART_NUM, chsize);
+	usart_set_sbmode(USART_NUM, sbmode);
+	usart_set_parity(USART_NUM, parity, form);
+
+	usart_enable(USART_NUM, 0);
+
+	current_baud = coding->dwDTERate;
+}
+
+#ifndef ENABLE_RTT
+void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
+{
+	(void)ep;
+
+	char buf[CDCACM_PACKET_SIZE];
+	int len = usbd_ep_read_packet(dev, CDCACM_UART_ENDPOINT,
+					buf, CDCACM_PACKET_SIZE);
+
+	gpio_set(LED_PORT_UART, LED_UART);
+	for(int i = 0; i < len; i++) {
+		usart_putc(buf[i]); 
+	}
+	gpio_clear(LED_PORT_UART, LED_UART);
+}
+#endif
+
+/* run by our systick timer */
+void uart_pop(void)
+{
+	if (cdcacm_get_config() != 1) {
+		return;
+	}
+
+        if (!qempty(rx.head, rx.tail)) {
+		if (usbd_ep_write_packet(usbdev, 0x83, &rx.buf[rx.tail], 1) == 0) {
+			return;
+		}
+		rx.tail = qinc(rx.tail, Q_SIZE);
+	}
+}
+
+void usbuart_usb_in_cb(usbd_device *dev, uint8_t ep)
+{
+	(void) dev;
+	(void) ep;
+}
+
+/************************** UART Interrupt Handlers *************************/
+static void uart_rx_irq(void)
+{
+	char c = UART(USART_NUM)->data;
+
+	/* bug?, need to re-enable rx complete interrupt */
+	INSERTBF(UART_INTENSET_RXC, 1, UART(USART_NUM)->intenset);
+
+	if (!qfull(rx.head, rx.tail, Q_SIZE)) {
+		rx.buf[rx.head] = c;
+		rx.head = qinc(rx.head, Q_SIZE);
+	}
+}
+
+static void uart_tx_irq(void)
+{
+	if (!qempty(tx.head, tx.tail)) {
+		usart_send(USART_NUM, tx.buf[tx.tail]);
+		tx.tail = qinc(tx.tail, Q_SIZE);
+	} else {
+		usart_disable_tx_interrupt(USART_NUM);
+	}
+}
+
+void sercom0_isr(void)
+{
+	/* Turn on LED */
+	gpio_set(LED_PORT_UART, LED_UART);
+
+	if (GETBF(UART_INTFLAG_RXC, UART(USART_NUM)->intflag))
+		uart_rx_irq();
+
+	if (GETBF(UART_INTFLAG_DRE, UART(USART_NUM)->intflag))
+		uart_tx_irq();
+}
+
+void sercom1_isr(void)
+{
+
+	/* Turn on LED */
+	gpio_set(LED_PORT_UART, LED_UART);
+
+	if (GETBF(UART_INTFLAG_RXC, UART(USART_NUM)->intflag))
+		uart_rx_irq();
+
+	if (GETBF(UART_INTFLAG_DRE, UART(USART_NUM)->intflag))
+		uart_tx_irq();
+}
--- a/src/platforms/stm32/rtt_if.c
+++ b/src/platforms/stm32/rtt_if.c
@ -0,0 +1,134 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "general.h"
+#include "platform.h"
+#include <assert.h>
+#include "cdcacm.h"
+#include "rtt.h"
+#include "rtt_if.h"
+
+/*********************************************************************
+*
+*       rtt terminal i/o
+*
+**********************************************************************
+*/
+
+/* usb uart receive buffer */
+static char recv_buf[RTT_DOWN_BUF_SIZE];
+static uint32_t recv_head = 0;
+static uint32_t recv_tail = 0;
+
+/* data from host to target: number of free bytes in usb receive buffer */
+inline static uint32_t recv_bytes_free()
+{
+	if (recv_tail <= recv_head)
+		return sizeof(recv_buf) - recv_head + recv_tail - 1;
+	else
+		return recv_tail - recv_head - 1;
+}
+
+/* data from host to target: true if not enough free buffer space and we need to close flow control */
+inline static bool recv_set_nak()
+{
+	assert(sizeof(recv_buf) > 2 * CDCACM_PACKET_SIZE);
+	return recv_bytes_free() < 2 * CDCACM_PACKET_SIZE;
+}
+
+/* usbuart_usb_out_cb is called when usb uart has received new data for target.
+   this routine has to be fast */
+
+void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
+{
+	(void)dev;
+	(void)ep;
+	char usb_buf[CDCACM_PACKET_SIZE];
+
+	/* close flow control while processing packet */
+	usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 1);
+
+	const uint16_t len = usbd_ep_read_packet(usbdev, CDCACM_UART_ENDPOINT, usb_buf, CDCACM_PACKET_SIZE);
+
+	/* skip flag: drop packet if not enough free buffer space */
+	if (rtt_flag_skip && len > recv_bytes_free()) {
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+		return;
+	}
+
+	/* copy data to recv_buf */
+	for (int i = 0; i < len; i++) {
+		uint32_t next_recv_head = (recv_head + 1) % sizeof(recv_buf);
+		if (next_recv_head == recv_tail)
+			break; /* overflow */
+		recv_buf[recv_head] = usb_buf[i];
+		recv_head = next_recv_head;
+	}
+
+	/* block flag: flow control closed if not enough free buffer space */
+	if (!(rtt_flag_block && recv_set_nak()))
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+
+	return;
+}
+
+/* rtt host to target: read one character */
+int32_t rtt_getchar()
+{
+	int retval;
+
+	if (recv_head == recv_tail)
+		return -1;
+	retval = recv_buf[recv_tail];
+	recv_tail = (recv_tail + 1) % sizeof(recv_buf);
+
+	/* open flow control if enough free buffer space */
+	if (!recv_set_nak())
+		usbd_ep_nak_set(usbdev, CDCACM_UART_ENDPOINT, 0);
+
+	return retval;
+}
+
+/* rtt host to target: true if no characters available for reading */
+bool rtt_nodata()
+{
+	return recv_head == recv_tail;
+}
+
+/* rtt target to host: write string */
+uint32_t rtt_write(const char *buf, uint32_t len)
+{
+	if (len != 0 && usbdev && cdcacm_get_config() && cdcacm_get_dtr()) {
+		for (uint32_t p = 0; p < len; p += CDCACM_PACKET_SIZE) {
+			uint32_t plen = MIN(CDCACM_PACKET_SIZE, len - p);
+			while(usbd_ep_write_packet(usbdev, CDCACM_UART_ENDPOINT, buf + p, plen) <= 0);
+		}
+		/* flush 64-byte packet on full-speed */
+		if (CDCACM_PACKET_SIZE == 64 && (len % CDCACM_PACKET_SIZE) == 0)
+			while(usbd_ep_write_packet(usbdev, CDCACM_UART_ENDPOINT, NULL, 0) <= 0);
+	}
+	return len;
+}
--- a/src/platforms/stm32/usbuart.c
+++ b/src/platforms/stm32/usbuart.c
@ -259,6 +259,7 @@ static void usbuart_change_dma_tx_buf(void)
 	buf_tx_act_idx ^= 1;
 }

+#ifndef ENABLE_RTT
 void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 {
 	(void)ep;
@ -301,6 +302,7 @@ void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 	if (TX_BUF_SIZE - buf_tx_act_sz >= CDCACM_PACKET_SIZE)
 		usbd_ep_nak_set(dev, CDCACM_UART_ENDPOINT, 0);
 }
+#endif

 #ifdef USBUART_DEBUG
 int usbuart_debug_write(const char *buf, size_t len)
--- a/src/platforms/tm4c/usbuart.c
+++ b/src/platforms/tm4c/usbuart.c
@ -99,6 +99,7 @@ void usbuart_set_line_coding(struct usb_cdc_line_coding *coding)
 	}
 }

+#ifndef ENABLE_RTT
 void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 {
 	(void)ep;
@ -110,7 +111,7 @@ void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 	for(int i = 0; i < len; i++)
 		uart_send_blocking(USBUART, buf[i]);
 }
-
+#endif

 void usbuart_usb_in_cb(usbd_device *dev, uint8_t ep)
 {
--- a/src/rtt.c
+++ b/src/rtt.c
@ -0,0 +1,456 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "general.h"
+#include "platform.h"
+#include "gdb_packet.h"
+#include "target.h"
+#include "target/target_internal.h"
+#include "rtt.h"
+#include "rtt_if.h"
+
+bool rtt_enabled = false;
+bool rtt_found = false;
+static bool rtt_halt = false; // true if rtt needs to halt target to access memory
+uint32_t rtt_cbaddr = 0;
+bool rtt_auto_channel = true;
+struct rtt_channel_struct rtt_channel[MAX_RTT_CHAN];
+
+uint32_t rtt_min_poll_ms = 8;    /* 8 ms */
+uint32_t rtt_max_poll_ms = 256;  /* 0.256 s */
+uint32_t rtt_max_poll_errs = 10;
+static uint32_t poll_ms;
+static uint32_t poll_errs;
+static uint32_t last_poll_ms;
+/* flags for data from host to target */
+bool rtt_flag_skip = false;
+bool rtt_flag_block = false;
+
+typedef enum rtt_retval {
+	RTT_OK,
+	RTT_IDLE,
+	RTT_ERR
+} rtt_retval;
+
+#ifdef RTT_IDENT
+#define Q(x) #x
+#define QUOTE(x) Q(x)
+char rtt_ident[16] = QUOTE(RTT_IDENT);
+#else
+char rtt_ident[16] = {0};
+#endif
+
+/* usb uart transmit buffer */
+static char xmit_buf[RTT_UP_BUF_SIZE];
+
+/*********************************************************************
+*
+*       rtt control block
+*
+**********************************************************************
+*/
+
+uint32_t fastsrch(target *cur_target)
+{
+	const uint32_t m = 16;
+	const uint64_t q = 0x797a9691; /* prime */
+	const uint64_t rm = 0x73b07d01;
+	const uint64_t p = 0x444110cd;
+	const uint32_t stride = 128;
+	uint64_t t = 0;
+	uint8_t srch_buf[m+stride];
+
+	for (struct target_ram *r = cur_target->ram; r; r = r->next) {
+		const uint32_t ram_start = r->start;
+		const uint32_t ram_end = r->start + r->length;
+
+		t = 0;
+		memset(srch_buf, 0, sizeof(srch_buf));
+
+		for (uint32_t addr = ram_start; addr < ram_end; addr += stride) {
+			uint32_t buf_siz = MIN(stride, ram_end - addr);
+			memcpy(srch_buf, srch_buf + stride, m);
+			if (target_mem_read(cur_target, srch_buf + m, addr, buf_siz)) {
+				gdb_outf("rtt: read fail at 0x%" PRIx32 "\r\n", addr);
+				return 0;
+			}
+			for (uint32_t i = 0; i < buf_siz; i++) {
+				t = (t + q - rm * srch_buf[i] % q) % q;
+				t = ((t << 8) + srch_buf[i + m]) % q;
+				if (p == t) {
+					uint32_t offset =  i - m + 1;
+					return addr + offset;
+				}
+			}
+		}
+	}
+	/* no match */
+	return 0;
+}
+
+uint32_t memsrch(target *cur_target)
+{
+	char *srch_str = rtt_ident;
+	uint32_t srch_str_len = strlen(srch_str);
+	uint8_t srch_buf[128];
+
+	if (srch_str_len == 0 || srch_str_len > sizeof(srch_buf) / 2)
+		return 0;
+
+	if (rtt_cbaddr && !target_mem_read(cur_target, srch_buf, rtt_cbaddr, srch_str_len)
+		&& strncmp((const char *)(srch_buf), srch_str, srch_str_len) == 0)
+		/* still at same place */
+		return rtt_cbaddr;
+
+	for (struct target_ram *r = cur_target->ram; r; r = r->next) {
+		uint32_t ram_end = r->start + r->length;
+		for (uint32_t addr = r->start; addr < ram_end; addr += sizeof(srch_buf) - srch_str_len - 1) {
+			uint32_t buf_siz = MIN(ram_end - addr, sizeof(srch_buf));
+			if (target_mem_read(cur_target, srch_buf, addr, buf_siz)) {
+				gdb_outf("rtt: read fail at 0x%" PRIx32 "\r\n", addr);
+				continue;
+			}
+			for (uint32_t offset = 0; offset + srch_str_len + 1 < buf_siz; offset++) {
+				if (strncmp((const char *)(srch_buf + offset), srch_str, srch_str_len) == 0) {
+					uint32_t cb_addr = addr + offset;
+					return cb_addr;
+				}
+			}
+		}
+	}
+	return 0;
+}
+
+static void find_rtt(target *cur_target)
+{
+	rtt_found = false;
+	poll_ms = rtt_max_poll_ms;
+	poll_errs = 0;
+	last_poll_ms = 0;
+
+	if (!cur_target || !rtt_enabled)
+		return;
+
+	if (rtt_ident[0] == 0)
+		rtt_cbaddr = fastsrch(cur_target);
+	else
+		rtt_cbaddr = memsrch(cur_target);
+	DEBUG_INFO("rtt: match at 0x%" PRIx32 "\r\n", rtt_cbaddr);
+
+	if (rtt_cbaddr) {
+		uint32_t num_buf[2];
+		int32_t num_up_buf;
+		int32_t num_down_buf;
+		if (target_mem_read(cur_target, num_buf, rtt_cbaddr + 16, sizeof(num_buf)))
+			return;
+		num_up_buf = num_buf[0];
+		num_down_buf = num_buf[1];
+
+		if (num_up_buf > 255 || num_down_buf > 255) {
+			gdb_out("rtt: bad cblock\r\n");
+			rtt_enabled = false;
+			return;
+		} else if (num_up_buf == 0 && num_down_buf == 0)
+			gdb_out("rtt: empty cblock\r\n");
+
+		for (int32_t i = 0; i < MAX_RTT_CHAN; i++) {
+			uint32_t buf_desc[6];
+
+			rtt_channel[i].is_configured = false;
+			rtt_channel[i].is_output = false;
+			rtt_channel[i].buf_addr = 0;
+			rtt_channel[i].buf_size = 0;
+			rtt_channel[i].head_addr = 0;
+			rtt_channel[i].tail_addr = 0;
+			rtt_channel[i].flag = 0;
+
+			if (i >= num_up_buf + num_down_buf)
+				continue;
+			if (target_mem_read(cur_target, buf_desc, rtt_cbaddr + 24 + i * 24, sizeof(buf_desc)))
+				return;
+			rtt_channel[i].is_output = i < num_up_buf;
+			rtt_channel[i].buf_addr = buf_desc[1];
+			rtt_channel[i].buf_size = buf_desc[2];
+			rtt_channel[i].head_addr = rtt_cbaddr + 24 + i * 24 + 12;
+			rtt_channel[i].tail_addr = rtt_cbaddr + 24 + i * 24 + 16;
+			rtt_channel[i].flag = buf_desc[5];
+			rtt_channel[i].is_configured = (rtt_channel[i].buf_addr != 0) && (rtt_channel[i].buf_size != 0);
+		}
+
+		/* auto channel: enable output channels 0 and 1 and first input channel */
+		if (rtt_auto_channel) {
+			for (uint32_t i = 0; i < MAX_RTT_CHAN; i++)
+				rtt_channel[i].is_enabled = false;
+			rtt_channel[0].is_enabled = num_up_buf > 0;
+			rtt_channel[1].is_enabled = num_up_buf > 1;
+			if ((num_up_buf < MAX_RTT_CHAN) && (num_down_buf > 0))
+				rtt_channel[num_up_buf].is_enabled = true;
+		}
+
+		/* get flags for data from host to target */
+		rtt_flag_skip = false;
+		rtt_flag_block = false;
+		for (uint32_t i = 0; i < MAX_RTT_CHAN; i++)
+			if (rtt_channel[i].is_enabled && rtt_channel[i].is_configured && !rtt_channel[i].is_output) {
+				rtt_flag_skip = rtt_channel[i].flag == 0;
+				rtt_flag_block = rtt_channel[i].flag == 2;
+				break;
+			}
+
+		rtt_found = true;
+		DEBUG_INFO("rtt found\n");
+	}
+	return;
+}
+
+/*********************************************************************
+*
+*       rtt from host to target
+*
+**********************************************************************
+*/
+
+/* poll if host has new data for target */
+static rtt_retval read_rtt(target *cur_target, uint32_t i)
+{
+	uint32_t head_tail[2];
+	uint32_t buf_head;
+	uint32_t buf_tail;
+	uint32_t next_head;
+	int ch;
+
+	/* copy data from recv_buf to target rtt 'down' buffer */
+	if (rtt_nodata())
+		return RTT_IDLE;
+
+	if (cur_target == NULL || rtt_channel[i].is_output || rtt_channel[i].buf_addr == 0 || rtt_channel[i].buf_size == 0)
+		return RTT_IDLE;
+
+	/* read down buffer head and tail from target */
+	if (target_mem_read(cur_target, head_tail, rtt_channel[i].head_addr, sizeof(head_tail)))
+		return RTT_ERR;
+
+	buf_head = head_tail[0];
+	buf_tail = head_tail[1];
+
+	if (buf_head >= rtt_channel[i].buf_size || buf_tail >= rtt_channel[i].buf_size)
+		return RTT_ERR;
+
+	/* write recv_buf to target rtt 'down' buf */
+	while ((next_head = ((buf_head + 1) % rtt_channel[i].buf_size)) != buf_tail && (ch = rtt_getchar()) != -1) {
+		if (target_mem_write(cur_target, rtt_channel[i].buf_addr + buf_head, &ch, 1))
+			return RTT_ERR;
+
+		/* advance pointers */
+		buf_head = next_head;
+	}
+
+	/* update head of target 'down' buffer */
+	if (target_mem_write(cur_target, rtt_channel[i].head_addr, &buf_head, sizeof(buf_head)))
+		return RTT_ERR;
+	return RTT_OK;
+}
+
+
+/*********************************************************************
+*
+*       rtt from target to host
+*
+**********************************************************************
+*/
+
+/* target_mem_read, word aligned for speed.
+   note: dest has to be len + 8 bytes, to allow for alignment and padding.
+ */
+int target_aligned_mem_read(target *t, void *dest, target_addr src, size_t len)
+{
+	uint32_t src0 = src;
+	uint32_t len0 = len;
+	uint32_t offset = src & 0x3;
+	src0 -= offset;
+	len0 += offset;
+	if ((len0 & 0x3) != 0)
+		len0 = (len0 + 4) & ~0x3;
+
+	if (src0 == src && len0 == len)
+		return target_mem_read(t, dest, src, len);
+	else {
+		uint32_t retval = target_mem_read(t, dest, src0, len0);
+		memmove(dest, dest + offset, len);
+		return retval;
+	}
+}
+
+/* poll if target has new data for host */
+static rtt_retval print_rtt(target *cur_target, uint32_t i)
+{
+	uint32_t head;
+	uint32_t tail;
+
+	if (!cur_target || !rtt_channel[i].is_output || rtt_channel[i].buf_addr == 0 || rtt_channel[i].head_addr == 0)
+		return RTT_IDLE;
+
+	uint32_t head_tail[2];
+	if (target_mem_read(cur_target, head_tail, rtt_channel[i].head_addr, sizeof(head_tail)))
+		return RTT_ERR;
+	head = head_tail[0];
+	tail = head_tail[1];
+
+	if (head >= rtt_channel[i].buf_size || tail >= rtt_channel[i].buf_size)
+		return RTT_ERR;
+	else if (head == tail)
+		return RTT_IDLE;
+
+	uint32_t bytes_free = sizeof(xmit_buf) - 8; /* need 8 bytes for alignment and padding */
+	uint32_t bytes_read = 0;
+
+	if (tail > head) {
+		uint32_t len = rtt_channel[i].buf_size - tail;
+		if (len > bytes_free)
+			len = bytes_free;
+		if (target_aligned_mem_read(cur_target, xmit_buf + bytes_read, rtt_channel[i].buf_addr + tail, len))
+			return RTT_ERR;
+		bytes_free -= len;
+		bytes_read += len;
+		tail = (tail + len) % rtt_channel[i].buf_size;
+	}
+
+	if (head > tail && bytes_free > 0) {
+		uint32_t len = head - tail;
+		if (len > bytes_free)
+			len = bytes_free;
+		if (target_aligned_mem_read(cur_target, xmit_buf + bytes_read, rtt_channel[i].buf_addr + tail, len))
+			return RTT_ERR;
+		bytes_read += len;
+		tail = (tail + len) % rtt_channel[i].buf_size;
+	}
+
+	/* update tail on target */
+	if (target_mem_write(cur_target, rtt_channel[i].tail_addr, &tail, sizeof(tail)))
+		return RTT_ERR;
+
+	/* write buffer to usb */
+	rtt_write(xmit_buf, bytes_read);
+
+	return RTT_OK;
+}
+
+
+/*********************************************************************
+*
+*       target background memory access
+*
+**********************************************************************
+*/
+
+/* target_no_background_memory_access() is true if the target needs to be halted during jtag memory access
+   target_no_background_memory_access() is false if the target allows jtag memory access while running */
+
+bool target_no_background_memory_access(target *cur_target)
+{
+	/* if error message is 'rtt: read fail at' add target to expression below.
+	   As a first approximation, assume all arm processors allow memory access while running, and no riscv does. */
+	bool riscv_core = cur_target && target_core_name(cur_target) && strstr(target_core_name(cur_target), "RVDBG");
+	return riscv_core;
+}
+
+/*********************************************************************
+*
+*       rtt top level
+*
+**********************************************************************
+*/
+
+void poll_rtt(target *cur_target)
+{
+	/* rtt off */
+	if (!cur_target || !rtt_enabled)
+		return;
+	/* target present and rtt enabled */
+	uint32_t now = platform_time_ms();
+	bool rtt_err = false;
+	bool rtt_busy = false;
+
+	if (last_poll_ms + poll_ms <= now || now < last_poll_ms) {
+		target_addr watch;
+		enum target_halt_reason reason;
+		bool resume_target = false;
+		if (!rtt_found)
+			/* check if target needs to be halted during memory access */
+			rtt_halt = target_no_background_memory_access(cur_target);
+		if (rtt_halt && target_halt_poll(cur_target, &watch) == TARGET_HALT_RUNNING) {
+			/* briefly halt target during target memory access */
+			target_halt_request(cur_target);
+			while((reason = target_halt_poll(cur_target, &watch)) == TARGET_HALT_RUNNING)
+				continue;
+			resume_target = reason == TARGET_HALT_REQUEST;
+		}
+		if (!rtt_found)
+			/* find rtt control block in target memory */
+			find_rtt(cur_target);
+		/* do rtt i/o if control block found */
+		if (rtt_found) {
+			for (uint32_t i = 0; i < MAX_RTT_CHAN; i++) {
+				rtt_retval v;
+				if (rtt_channel[i].is_enabled && rtt_channel[i].is_configured) {
+					if (rtt_channel[i].is_output)
+						v = print_rtt(cur_target, i);
+					else
+						v = read_rtt(cur_target, i);
+					if (v == RTT_OK) rtt_busy = true;
+					else if (v == RTT_ERR) rtt_err = true;
+				}
+			}
+		}
+		/* continue target if halted */
+		if (resume_target)
+			target_halt_resume(cur_target, false);
+
+		/* update last poll time */
+		last_poll_ms = now;
+
+		/* rtt polling frequency goes up and down with rtt activity */
+		if (rtt_busy && !rtt_err)
+			poll_ms /= 2;
+		else
+			poll_ms *= 2;
+
+		if (poll_ms > rtt_max_poll_ms)
+			poll_ms = rtt_max_poll_ms;
+		else if (poll_ms < rtt_min_poll_ms)
+			poll_ms = rtt_min_poll_ms;
+
+		if (rtt_err) {
+			gdb_out("rtt: err\r\n");
+			poll_errs++;
+			if (rtt_max_poll_errs != 0 && poll_errs > rtt_max_poll_errs) {
+				gdb_out("\r\nrtt lost\r\n");
+				rtt_enabled = false;
+			}
+		}
+	}
+	return;
+}
--- a/src/target/adiv5_swdp.c
+++ b/src/target/adiv5_swdp.c
@ -68,7 +68,7 @@ bool firmware_dp_low_write(ADIv5_DP_t *dp, uint16_t addr, const uint32_t data)
 int adiv5_swdp_scan(uint32_t targetid)
 {
 	volatile struct exception e;
-	target_list_free();
+	static bool scan_multidrop = true;
 	ADIv5_DP_t idp = {
 		.dp_low_write = firmware_dp_low_write,
 		.error = firmware_swdp_error,
@ -77,6 +77,7 @@ int adiv5_swdp_scan(uint32_t targetid)
 		.abort = firmware_swdp_abort,
 	};
 	ADIv5_DP_t *initial_dp = &idp;
+	target_list_free();
 	if (swdptap_init(initial_dp))
 		return -1;
 	/* DORMANT-> SWD sequence*/
@ -93,7 +94,6 @@ int adiv5_swdp_scan(uint32_t targetid)
 	initial_dp->seq_out(0x1a0, 12);
 	uint32_t idcode = 0;
 	volatile uint32_t target_id = 0;
-	bool scan_multidrop = true;
 	if (!targetid || !initial_dp->dp_low_write) {
 		/* No targetID given on the command line or probe can not
 		 * handle multi-drop. Try to read ID */