diff --git a/src/platforms/hosted/bmp_libusb.c b/src/platforms/hosted/bmp_libusb.c
index e24bdda6..e29344b8 100644
--- a/src/platforms/hosted/bmp_libusb.c
+++ b/src/platforms/hosted/bmp_libusb.c
@@ -142,6 +142,8 @@ int find_debuggers(BMP_CL_OPTIONS_t *cl_opts,bmp_info_t *info)
 			libusb_close(handle);
 			continue;
 		}
+		if (res < 0)
+			serial[0] = 0;
 		res = libusb_get_string_descriptor_ascii(
 			handle, desc.iManufacturer, (uint8_t*)manufacturer,
 			sizeof(manufacturer));
@@ -231,6 +233,8 @@ int find_debuggers(BMP_CL_OPTIONS_t *cl_opts,bmp_info_t *info)
 			if (!cable->name)
 				continue;
 		}
+		if (!serial[0])
+			strcpy(serial, "<no serial number>");
 		if (report) {
 			DEBUG_WARN("%2d: %s, %s, %s\n", found_debuggers + 1,
 				   serial,
diff --git a/src/platforms/hosted/bmp_serial.c b/src/platforms/hosted/bmp_serial.c
index 098c1477..b1050bd2 100644
--- a/src/platforms/hosted/bmp_serial.c
+++ b/src/platforms/hosted/bmp_serial.c
@@ -209,15 +209,12 @@ static int scan_linux_id(char *name, char *type, char *version, char  *serial)
 
 int find_debuggers(BMP_CL_OPTIONS_t *cl_opts, bmp_info_t *info)
 {
-	char name[4096];
 	if (cl_opts->opt_device)
 		return 1;
 	info->bmp_type = BMP_TYPE_BMP;
 	DIR *dir = opendir(DEVICE_BY_ID);
-	if (!dir) {
-		DEBUG_WARN("Could not opendir %s: %s\n", name, strerror(errno));
-		return -1;
-	}
+	if (!dir) /* No serial device connected!*/
+		return 0;
 	int found_bmps = 0;
 	struct dirent *dp;
 	int i = 0;
diff --git a/src/platforms/pc/cl_utils.c b/src/platforms/pc/cl_utils.c
index e27fe59e..6283d561 100644
--- a/src/platforms/pc/cl_utils.c
+++ b/src/platforms/pc/cl_utils.c
@@ -31,6 +31,7 @@
 #include "version.h"
 #include "target.h"
 #include "target_internal.h"
+#include "cortexm.h"
 
 #include "cl_utils.h"
 #include "bmp_hosted.h"
@@ -140,6 +141,8 @@ static void cl_help(char **argv)
 	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-T\t\t: Continious read/write-back some value to allow\n"
+			   "\t\t\t  timing insection of SWJ. Abort with ^C\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");
@@ -163,7 +166,7 @@ void cl_init(BMP_CL_OPTIONS_t *opt, int argc, char **argv)
 	opt->opt_target_dev = 1;
 	opt->opt_flash_size = 16 * 1024 *1024;
 	opt->opt_flash_start = 0xffffffff;
-	while((c = getopt(argc, argv, "eEhHv:d:s:I:c:CnltVta:S:jpP:rR")) != -1) {
+	while((c = getopt(argc, argv, "eEhHv:d:s:I:c:CnltVtTa:S:jpP:rR")) != -1) {
 		switch(c) {
 		case 'c':
 			if (optarg)
@@ -212,6 +215,9 @@ void cl_init(BMP_CL_OPTIONS_t *opt, int argc, char **argv)
 			opt->opt_mode = BMP_MODE_TEST;
 			cl_debuglevel |= BMP_DEBUG_INFO | BMP_DEBUG_STDOUT;
 			break;
+		case 'T':
+			opt->opt_mode = BMP_MODE_SWJ_TEST;
+			break;
 		case 'V':
 			opt->opt_mode = BMP_MODE_FLASH_VERIFY;
 			break;
@@ -262,6 +268,7 @@ void cl_init(BMP_CL_OPTIONS_t *opt, int argc, char **argv)
 	}
 	/* Checks */
 	if ((opt->opt_flash_file) && ((opt->opt_mode == BMP_MODE_TEST ) ||
+								  (opt->opt_mode == BMP_MODE_SWJ_TEST) ||
 								  (opt->opt_mode == BMP_MODE_RESET))) {
 		DEBUG_WARN("Ignoring filename in reset/test mode\n");
 		opt->opt_flash_file = NULL;
@@ -369,7 +376,22 @@ int cl_execute(BMP_CL_OPTIONS_t *opt)
 	}
 	if (opt->opt_flash_start == 0xffffffff)
 		opt->opt_flash_start = flash_start;
-	if (opt->opt_mode == BMP_MODE_TEST)
+	if (opt->opt_mode == BMP_MODE_SWJ_TEST) {
+		switch (t->core[0]) {
+		case 'M':
+			DEBUG_WARN("Continious read/write-back DEMCR. Abort with ^C\n");
+			while(1) {
+				uint32_t demcr;
+				target_mem_read(t, &demcr, CORTEXM_DEMCR, 4);
+				target_mem_write32(t, CORTEXM_DEMCR, demcr);
+				platform_delay(1); /* To allow trigger*/
+			}
+		default:
+			DEBUG_WARN("No test for this core type yet\n");
+		}
+	}
+	if ((opt->opt_mode == BMP_MODE_TEST) ||
+		(opt->opt_mode == BMP_MODE_SWJ_TEST))
 		goto target_detach;
 	int read_file = -1;
 	if ((opt->opt_mode == BMP_MODE_FLASH_WRITE) ||
diff --git a/src/platforms/pc/cl_utils.h b/src/platforms/pc/cl_utils.h
index e7349c71..6cff3b81 100644
--- a/src/platforms/pc/cl_utils.h
+++ b/src/platforms/pc/cl_utils.h
@@ -33,7 +33,8 @@ enum bmp_cl_mode {
 	BMP_MODE_FLASH_ERASE,
 	BMP_MODE_FLASH_WRITE,
 	BMP_MODE_FLASH_READ,
-	BMP_MODE_FLASH_VERIFY
+	BMP_MODE_FLASH_VERIFY,
+	BMP_MODE_SWJ_TEST,
 };
 
 typedef struct BMP_CL_OPTIONS_s {
diff --git a/src/target/cortexm.c b/src/target/cortexm.c
index f717073e..d7c72898 100644
--- a/src/target/cortexm.c
+++ b/src/target/cortexm.c
@@ -448,6 +448,8 @@ bool cortexm_probe(ADIv5_AP_t *ap)
 			PROBE(lpc43xx_probe);
 			PROBE(lpc546xx_probe);
 			PROBE(kinetis_probe); /* Older K-series */
+		} else if (ap->ap_partno == 0x4cb) { /* Cortex-M23 ROM */
+			PROBE(gd32f1_probe); /* GD32E23x uses GD32F1 peripherals */
 		}
 		/* Info on PIDR of these parts wanted! */
 		PROBE(sam3x_probe);
diff --git a/src/target/stm32f1.c b/src/target/stm32f1.c
index 53c347b2..a0ade734 100644
--- a/src/target/stm32f1.c
+++ b/src/target/stm32f1.c
@@ -123,8 +123,10 @@ static void stm32f1_add_flash(target *t,
 bool gd32f1_probe(target *t)
 {
 	uint16_t stored_idcode = t->idcode;
-	// M3 & M4 & riscV only afaik
-	t->idcode = target_mem_read32(t, DBGMCU_IDCODE) & 0xfff;
+	if ((t->cpuid & CPUID_PARTNO_MASK) == CORTEX_M23)
+		t->idcode = target_mem_read32(t, DBGMCU_IDCODE_F0) & 0xfff;
+	else
+		t->idcode = target_mem_read32(t, DBGMCU_IDCODE) & 0xfff;
 	uint32_t signature= target_mem_read32(t, FLASHSIZE);
 	uint32_t flashSize=signature & 0xFFFF;
 	uint32_t ramSize=signature >>16 ;
@@ -132,11 +134,14 @@ bool gd32f1_probe(target *t)
 	case 0x414:  /* Gigadevice gd32f303 */
 		t->driver = "GD32F3";
 		break;
-	case 0x410:  /* Gigadevice gd32f103 */
-        t->driver = "GD32F1";
+	case 0x410:  /* Gigadevice gd32f103, gd32e230 */
+		if ((t->cpuid & CPUID_PARTNO_MASK) == CORTEX_M23)
+			t->driver = "GD32E230";
+		else
+			t->driver = "GD32F1";
 		break;
 	default:
-        t->idcode = stored_idcode;
+		t->idcode = stored_idcode;
 		return false;
 	}
 	target_add_ram(t, 0x20000000, ramSize*1024);