brymen-dmm: unbreak BM85x communication by pulsing RTS after COM port open

[libsigrok.git] / src / hardware / brymen-dmm / api.c

diff --git a/src/hardware/brymen-dmm/api.c b/src/hardware/brymen-dmm/api.c
index ce6f1f33e4f4c8e832fa34232a74f04698d89f13..230b6adf4bd86692604e57501aaafa0c2a8c27d8 100644 (file)
--- 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);