From: Uwe Hermann <redacted>
Date: Tue, 6 Aug 2013 21:25:18 +0000 (+0200)
Subject: uni-t-dmm: Fix UT61E bug related to the UNI-T UD-D04 cable.
X-Git-Tag: libsigrok-0.2.1~12
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=4d7ddff75b8c23fc8d5355c480df029b130cec0c;p=libsigrok.git

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 dbab6da9..05c1c47e 100644
--- 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 aa8e0780..0c6d9efe 100644
--- 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) {