uni-t-dmm: Fix UT61E bug related to the UNI-T UD-D04 cable.

This fixes bug #136.

diff --git a/hardware/uni-t-dmm/api.c b/hardware/uni-t-dmm/api.c
index dbab6da95e6ef6261c96cc26eb1764613b63ecc8..05c1c47e4e0204c2b53ec9f4d771a3eaaacb37fa 100644 (file)
--- a/hardware/uni-t-dmm/api.c
+++ b/hardware/uni-t-dmm/api.c
@@ -76,7 +76,16 @@ SR_PRIV struct dmm_info udmms[] = {
                &uni_t_ut61d_driver_info, receive_data_UNI_T_UT61D,
        },
        {
-               "UNI-T", "UT61E", 19230,
+               /*
+                * Important: The actual baudrate of the Cyrustek ES51922 chip
+                * used in this DMM is 19230. However, the WCH CH9325 chip
+                * (UART to USB/HID) used in (some versions of) the UNI-T
+                * UT-D04 cable doesn't support 19230 baud. It only supports
+                * 19200, and setting an unsupported baudrate will result in
+                * the default of 2400 being used (which will not work with
+                * this DMM, of course).
+                */
+               "UNI-T", "UT61E", 19200,
                ES51922_PACKET_SIZE, NULL,
                sr_es51922_packet_valid, sr_es51922_parse,
                NULL,

diff --git a/hardware/uni-t-dmm/protocol.c b/hardware/uni-t-dmm/protocol.c
index aa8e078015c1aed18a2985d4b33a959d8fb7ed68..0c6d9efe414605ab8c7ca06e3f37cb5fe97abcb4 100644 (file)
--- a/hardware/uni-t-dmm/protocol.c
+++ b/hardware/uni-t-dmm/protocol.c
@@ -220,10 +220,24 @@ static int get_and_handle_data(struct sr_dev_inst *sdi, int dmm, void *info)
 
        devc->bufoffset = 0;
 
-       /* Append the 1-7 data bytes of this chunk to pbuf. */
+       /*
+        * Append the 1-7 data bytes of this chunk to pbuf.
+        *
+        * Special case:
+        * DMMs with Cyrustek ES51922 chip need serial settings of
+        * 19230/7o1. The WCH CH9325 UART to USB/HID chip used in (some
+        * versions of) the UNI-T UT-D04 cable however, will also send
+        * the parity bit to the host in the 8-byte data chunks. This bit
+        * is encoded in bit 7 of each of the 1-7 data bytes and must thus
+        * be removed in order for the actual ES51922 protocol parser to
+        * work properly.
+        */
        num_databytes_in_chunk = buf[0] & 0x0f;
-       for (i = 0; i < num_databytes_in_chunk; i++)
-               pbuf[devc->buflen++] = buf[1 + i];
+       for (i = 0; i < num_databytes_in_chunk; i++, devc->buflen++) {
+               pbuf[devc->buflen] = buf[1 + i];
+               if (udmms[dmm].packet_parse == sr_es51922_parse)
+                       pbuf[devc->buflen] &= ~(1 << 7);
+       }
 
        /* Now look for packets in that data. */
        while ((devc->buflen - devc->bufoffset) >= udmms[dmm].packet_size) {