libftfdi: Allow to specify external resistor SWD connection.

More explanations in src/platforms/hosted/Readme.md

src/platforms/hosted/Readme.md

@@ -13,19 +13,51 @@ connect to the BMP with the CDCACM GDB serial server. GDB functionality
 is the same, monitor option may vary.
 
 More arguments allow to
-### print information on the connected target "blackmagiv -t"
+### Print information on the connected target
-### directly flash a binary file at 0x0800000  "blackmagic <file.bin>"
+```
+blackmagic -t
+```
+### Directly flash a binary file at lowest flash address
+```
+blackmagic <file.bin>
+```
 or with the -S argument at some other address
-### read flash to binary file "blackmagic -r <file>.bin
+```
-### verify flash against binary file "blackmagic -V <file>.bin
+blackmagic -S 0x08002000 <file.bin>
-
+```
-Use "blackmagic -h" to see all options.
 
+### Read flash to binary file
+```
+blackmagic -r <file>.bin
+```
+### Verify flash against binary file
+```
+blackmagic -V <file>.bin
+```
+### Show more options
+```
+blackmagic -h"
+```
 ## Used libraries:
 ### libusb
 ### libftdi, for FTDI support
 ### hidapi-libusb, for CMSIS-DAP support
 
+## Compiling on windows
+
+You can crosscompile blackmagic for windows with mingw or on windows
+with cygwin. For compilation, headers for libftdi1 and libusb-1.0 are
+needed. For running, libftdi1.dll and libusb-1.0.dll are needed and
+the executable must be able to find them. Mingw on cygwin does not provide
+a libftdi package yet.
+
+To prepare libusb access to the ftdi device, run zadig https://zadig.akeo.ie/.
+Choose WinUSB(libusb-1.0) for the BMP Ftdi device.
+
+Running cygwin/blackmagic in a cygwin console, the program does not react
+on ^C. In another console, run "ps ax" to find the WINPID of the process
+and then "taskkill /F ?PID (WINPID)".
+
 ## Supported debuggers
 REMOTE_BMP is a "normal" BMP usb connected
 
@@ -39,6 +71,69 @@ REMOTE_BMP is a "normal" BMP usb connected
 | FTDI MPSSE   |   ++  | Requires a device descrition
 | JLINK        |    -  | Usefull to add BMP support for MCUs with built-in JLINK
 
+## Device matching
+As other USB dongles already connected to the host PC may use FTDI chips,
+cable descriptions are provided to match with the dongle.
+To match the dongle, at least USB VID/PID  that must match.
+If a description is given, the USB device must provide that string. If a
+serial number string is given on the command line, that number must match
+with serial number in the USB descriptor of the device.
+
+## FTDI connection possibilities:
+
+| Direct Connection     |
+| ----------------------|
+| MPSSE_SK --> JTAG_TCK |
+| MPSSE_DO --> JTAG_TDI |
+| MPSSE_DI <-- JTAG_TDO |
+| MPSSE_CS <-> JTAG_TMS |
+
+\+ JTAG and bitbanging SWD is possible<br>
+\- No level translation, no buffering, no isolation<br>
+Example: [Flossjtag](https://randomprojects.org/wiki/Floss-JTAG).
+
+| Resistor SWD           |
+|------------------------|
+| MPSSE_SK ---> JTAG_TCK |
+| MPSSE_DO -R-> JTAG_TMS |
+| MPSSE_DI <--- JTAG_TMS |
+
+BMP would allow direct MPSSE_DO ->JTAG_TMS connections as BMP tristates DO
+when reading. Resistor defeats contentions anyways. R is typical choosen
+in the range of 470R
+
+\+ MPSSE SWD possible<br>
+\- No Jtag, no level translation, no buffering, no isolation<br>
+
+|Direct buffered Connection|
+|--------------------------|
+| MPSSE_SK -B-> JTAG_TCK   |
+| MPSSE_DO -B-> JTAG_TDI   |
+| MPSSE_DI <-B- JTAG_TDO   |
+| MPSSE_CS -B-> JTAG_TMS   |
+
+\+ Only Jtag, buffered, possible level translation and isolation<br>
+\- No SWD<br>
+Example: [Turtelizer]http://www.ethernut.de/en/hardware/turtelizer/index.html)
+[schematics](http://www.ethernut.de/pdf/turtelizer20c-schematic.pdf)
+
+The 'r' command line arguments allows to specify an external SWD
+resistor connection added to some existing cable. Jtag is not possible
+together with the 'r' argument.
+
+### Many variants possible
+As the FTDI has more pins, these pins may be used to control
+enables of buffers and multiplexer selection in many variants.
+
+### Reset, Target voltage readback etc
+The additional pins may also control Reset functionality, provide
+information if target voltage is applied. etc.
+
+### Cable descriptions
+Please help to verify the cable description and give feedback on the
+cables already listed and propose other cable. A link to the schematics
+is welcome.
+
 ## Feedback
 ### Issues and Pull request on https://github.com/blacksphere/blackmagic/
 ### Discussions on Discord.

src/platforms/hosted/ftdi_bmp.c

@@ -238,6 +238,22 @@ int ftdi_bmp_init(BMP_CL_OPTIONS_t *cl_opts, bmp_info_t *info)
 
 	active_cable = &cable_desc[index];
 	memcpy(&active_state, &active_cable->init, sizeof(data_desc_t));
+	/* If swd_(read|write) is not given for the selected cable and
+	   the 'r' command line argument is give, assume resistor SWD
+	   connection.*/
+	if (cl_opts->external_resistor_swd &&
+		(active_cable->mpsse_swd_read.set_data_low  == 0) &&
+		(active_cable->mpsse_swd_read.clr_data_low  == 0) &&
+		(active_cable->mpsse_swd_read.set_data_high == 0) &&
+		(active_cable->mpsse_swd_read.clr_data_high == 0) &&
+		(active_cable->mpsse_swd_write.set_data_low  == 0) &&
+		(active_cable->mpsse_swd_write.clr_data_low  == 0) &&
+		(active_cable->mpsse_swd_write.set_data_high == 0) &&
+		(active_cable->mpsse_swd_write.clr_data_high == 0)) {
+			DEBUG_INFO("Using external resistor SWD\n");
+			active_cable->mpsse_swd_read.set_data_low = MPSSE_DO;
+			active_cable->mpsse_swd_write.set_data_low = MPSSE_DO;
+		}
 
 	DEBUG_WARN("Black Magic Probe for FTDI/MPSSE\n");
 	if(ftdic) {

src/platforms/pc/cl_utils.c

@@ -135,6 +135,8 @@ static void cl_help(char **argv, BMP_CL_OPTIONS_t *opt)
 	DEBUG_WARN("\t-C\t\t: Connect under reset\n");
 	DEBUG_WARN("\t-t\t\t: Scan SWD or JTAG and display information about \n"
 			   "\t\t\t  connected devices\n");
+	DEBUG_WARN("\t-e\t\t: Assume \"resistor SWD connection\" on FTDI: TDI\n"
+               "\t\t\t  connected to TMS, TDO to TDI with eventual resistor\n");
 	DEBUG_WARN("\t-E\t\t: Erase flash until flash end or for given size\n");
 	DEBUG_WARN("\t-V\t\t: Verify flash against binary file\n");
 	DEBUG_WARN("\t-r\t\t: Read flash and write to binary file\n");
@@ -154,7 +156,7 @@ void cl_init(BMP_CL_OPTIONS_t *opt, int argc, char **argv)
 	int c;
 	opt->opt_target_dev = 1;
 	opt->opt_flash_size = 16 * 1024 *1024;
-	while((c = getopt(argc, argv, "Ehv:d:s:I:c:CnltVta:S:jpP:rR")) != -1) {
+	while((c = getopt(argc, argv, "eEhv:d:s:I:c:CnltVta:S:jpP:rR")) != -1) {
 		switch(c) {
 		case 'c':
 			if (optarg)
@@ -177,6 +179,9 @@ void cl_init(BMP_CL_OPTIONS_t *opt, int argc, char **argv)
 		case 'C':
 			opt->opt_connect_under_reset = true;
 			break;
+		case 'e':
+			opt->external_resistor_swd = true;
+			break;
 		case 'd':
 			if (optarg)
 				opt->opt_device = optarg;

src/platforms/pc/cl_utils.h

@@ -42,6 +42,7 @@ typedef struct BMP_CL_OPTIONS_s {
 	bool opt_tpwr;
 	bool opt_list_only;
 	bool opt_connect_under_reset;
+	bool external_resistor_swd;
 	char *opt_flash_file;
 	char *opt_device;
 	char *opt_serial;