X-Git-Url: https://sigrok.org/gitweb/?p=libsigrok.git;a=blobdiff_plain;f=src%2Fhardware%2Fbrymen-dmm%2Fapi.c;h=dacbee889267f7949e4e18ca08daa20ef31110b3;hp=ce6f1f33e4f4c8e832fa34232a74f04698d89f13;hb=11addc897a86a039f72cefbebb5058611ad79102;hpb=00ed77f27c85462cae238ee433dbf0f606eaaf84

diff --git a/src/hardware/brymen-dmm/api.c b/src/hardware/brymen-dmm/api.c
index ce6f1f33..dacbee88 100644
--- a/src/hardware/brymen-dmm/api.c
+++ b/src/hardware/brymen-dmm/api.c
@@ -41,6 +41,7 @@ static GSList *brymen_scan(struct sr_dev_driver *di, const char *conn,
 	struct sr_dev_inst *sdi;
 	struct dev_context *devc;
 	struct sr_serial_dev_inst *serial;
+	int rts_toggle_delay_us;
 	GSList *devices;
 	int ret;
 	uint8_t buf[128];
@@ -50,6 +51,21 @@ static GSList *brymen_scan(struct sr_dev_driver *di, const char *conn,
 
 	if (serial_open(serial, SERIAL_RDWR) != SR_OK)
 		return NULL;
+	/*
+	 * The device requires an RTS *pulse* before communication.
+	 * The vendor's documentation recommends the following sequence:
+	 * Open the COM port, wait for 100ms, set RTS=1, wait for 100ms,
+	 * set RTS=0, wait for 100ms, set RTS=1, configure bitrate and
+	 * frame format, transmit request data, receive response data.
+	 */
+	rts_toggle_delay_us = 100 * 1000; /* 100ms */
+	g_usleep(rts_toggle_delay_us);
+	serial_set_handshake(serial, 1, -1);
+	g_usleep(rts_toggle_delay_us);
+	serial_set_handshake(serial, 0, -1);
+	g_usleep(rts_toggle_delay_us);
+	serial_set_handshake(serial, 1, -1);
+	g_usleep(rts_toggle_delay_us);
 
 	sr_info("Probing port %s.", conn);
 
@@ -95,7 +111,12 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
 
 	devices = NULL;
 
-	conn = serialcomm = NULL;
+	/*
+	 * BEWARE! Default 'conn' is not desirable when the device cannot
+	 * reliably get detected. Insist that users specify the port.
+	 */
+	conn = NULL;
+	serialcomm = "9600/8n1/dtr=1/rts=1";
 	for (l = options; l; l = l->next) {
 		src = l->data;
 		switch (src->key) {
@@ -110,10 +131,7 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
 	if (!conn)
 		return NULL;
 
-	if (serialcomm)
-		devices = brymen_scan(di, conn, serialcomm);
-	else
-		devices = brymen_scan(di, conn, "9600/8n1/dtr=1/rts=1");
+	devices = brymen_scan(di, conn, serialcomm);
 
 	return devices;
 }