serial-dmm, metex14: add support for multiple channels per DMM

Optionally create multiple analog channels in serial-dmm's scan()
routine. Allow the meters' parse routines to fill in more than one
analog value from the inspection of a single packet.

Use "large" (4 times 14 bytes) packets for the Metex M-3860M and the
PeakTech 4390A meters, and have those large packets parsed by wrapping
the routines for regular 14-byte Metex packets, and sending four values
to the session bus after reception of one large packet.

Thanks to Frank Stettner <frank-stettner@gmx.net> for testing and
fixing the initial implementation of this extension.

src/dmm/metex14.c

@@ -313,6 +313,25 @@ SR_PRIV gboolean sr_metex14_packet_valid(const uint8_t *buf)
 	return TRUE;
 }
 
+SR_PRIV gboolean sr_metex14_4packets_valid(const uint8_t *buf)
+{
+	struct metex14_info info;
+	size_t ch_idx;
+	const uint8_t *ch_buf;
+
+	ch_buf = buf;
+	for (ch_idx = 0; ch_idx < 4; ch_idx++) {
+		if (ch_buf[13] != '\r')
+			return FALSE;
+		memset(&info, 0x00, sizeof(info));
+		parse_flags((const char *)ch_buf, &info);
+		if (!flags_valid(&info))
+			return FALSE;
+		ch_buf += METEX14_PACKET_SIZE;
+	}
+	return TRUE;
+}
+
 /**
  * Parse a protocol packet.
  *
@@ -354,3 +373,34 @@ SR_PRIV int sr_metex14_parse(const uint8_t *buf, float *floatval,
 
 	return SR_OK;
 }
+
+/**
+ * Parse one out of four values of a four-display Metex14 variant.
+ *
+ * The caller's 'info' parameter can be used to track the channel index,
+ * as long as the information is kept across calls to the 14-byte packet
+ * parse routine (which clears the 'info' container).
+ *
+ * Since analog values have further details in the 'analog' parameter,
+ * passing multiple values per parse routine call is problematic. So we
+ * prefer the approach of passing one value per call, which is most
+ * reliable and shall fit every similar device with multiple displays.
+ *
+ * The meters which use this parse routine send one 14-byte packet per
+ * display. Each packet has the regular Metex14 layout.
+ */
+SR_PRIV int sr_metex14_4packets_parse(const uint8_t *buf, float *floatval,
+	struct sr_datafeed_analog *analog, void *info)
+{
+	struct metex14_info *info_local;
+	size_t ch_idx;
+	const uint8_t *ch_buf;
+	int rc;
+
+	info_local = info;
+	ch_idx = info_local->ch_idx;
+	ch_buf = buf + ch_idx * METEX14_PACKET_SIZE;
+	rc = sr_metex14_parse(ch_buf, floatval, analog, info);
+	info_local->ch_idx = ch_idx + 1;
+	return rc;
+}

src/hardware/serial-dmm/api.c

@@ -56,6 +56,8 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
 	int dropped, ret;
 	size_t len;
 	uint8_t buf[128];
+	size_t ch_idx;
+	char ch_name[12];
 
 	dmm = (struct dmm_info *)di;
 
@@ -131,7 +133,13 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
 	sdi->inst_type = SR_INST_SERIAL;
 	sdi->conn = serial;
 	sdi->priv = devc;
-	sr_channel_new(sdi, 0, SR_CHANNEL_ANALOG, TRUE, "P1");
+	dmm->channel_count = 1;
+	if (dmm->packet_parse == sr_metex14_4packets_parse)
+		dmm->channel_count = 4;
+	for (ch_idx = 0; ch_idx < dmm->channel_count; ch_idx++) {
+		snprintf(ch_name, sizeof(ch_name), "P%zu", ch_idx);
+		sr_channel_new(sdi, ch_idx, SR_CHANNEL_ANALOG, TRUE, ch_name);
+	}
 	devices = g_slist_append(devices, sdi);
 
 scan_cleanup:
@@ -197,7 +205,7 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
 			.context = NULL, \
 		}, \
 		VENDOR, MODEL, CONN, BAUDRATE, PACKETSIZE, TIMEOUT, DELAY, \
-		REQUEST, VALID, PARSE, DETAILS, sizeof(struct CHIPSET##_info) \
+		REQUEST, 1, VALID, PARSE, DETAILS, sizeof(struct CHIPSET##_info) \
 	}).di
 
 SR_REGISTER_DEV_DRIVER_LIST(serial_dmm_drivers,
@@ -440,8 +448,8 @@ SR_REGISTER_DEV_DRIVER_LIST(serial_dmm_drivers,
 	DMM(
 		"metex-m3860m", metex14,
 		"Metex", "M-3860M", "9600/7n2/rts=0/dtr=1", 9600,
-		METEX14_PACKET_SIZE, 0, 0, sr_metex14_packet_request,
-		sr_metex14_packet_valid, sr_metex14_parse,
+		4 * METEX14_PACKET_SIZE, 0, 0, sr_metex14_packet_request,
+		sr_metex14_4packets_valid, sr_metex14_4packets_parse,
 		NULL
 	),
 	DMM(
@@ -475,8 +483,8 @@ SR_REGISTER_DEV_DRIVER_LIST(serial_dmm_drivers,
 	DMM(
 		"peaktech-4390a", metex14,
 		"PeakTech", "4390A", "9600/7n2/rts=0/dtr=1", 9600,
-		METEX14_PACKET_SIZE, 0, 0, sr_metex14_packet_request,
-		sr_metex14_packet_valid, sr_metex14_parse,
+		4 * METEX14_PACKET_SIZE, 0, 0, sr_metex14_packet_request,
+		sr_metex14_4packets_valid, sr_metex14_4packets_parse,
 		NULL
 	),
 	DMM(

src/hardware/serial-dmm/protocol.c

@@ -49,31 +49,42 @@ static void handle_packet(const uint8_t *buf, struct sr_dev_inst *sdi,
 	struct sr_analog_meaning meaning;
 	struct sr_analog_spec spec;
 	struct dev_context *devc;
+	gboolean sent_sample;
+	size_t ch_idx;
 
 	dmm = (struct dmm_info *)sdi->driver;
 
 	log_dmm_packet(buf);
 	devc = sdi->priv;
 
-	/* Note: digits/spec_digits will be overridden by the DMM parsers. */
-	sr_analog_init(&analog, &encoding, &meaning, &spec, 0);
+	sent_sample = FALSE;
+	memset(info, 0, dmm->info_size);
+	for (ch_idx = 0; ch_idx < dmm->channel_count; ch_idx++) {
+		/* Note: digits/spec_digits will be overridden by the DMM parsers. */
+		sr_analog_init(&analog, &encoding, &meaning, &spec, 0);
 
-	analog.meaning->channels = sdi->channels;
-	analog.num_samples = 1;
-	analog.meaning->mq = 0;
+		analog.meaning->channels =
+			g_slist_append(NULL, g_slist_nth_data(sdi->channels, ch_idx));
+		analog.num_samples = 1;
+		analog.meaning->mq = 0;
 
-	dmm->packet_parse(buf, &floatval, &analog, info);
-	analog.data = &floatval;
+		dmm->packet_parse(buf, &floatval, &analog, info);
+		analog.data = &floatval;
 
-	/* If this DMM needs additional handling, call the resp. function. */
-	if (dmm->dmm_details)
-		dmm->dmm_details(&analog, info);
+		/* If this DMM needs additional handling, call the resp. function. */
+		if (dmm->dmm_details)
+			dmm->dmm_details(&analog, info);
 
-	if (analog.meaning->mq != 0) {
-		/* Got a measurement. */
-		packet.type = SR_DF_ANALOG;
-		packet.payload = &analog;
-		sr_session_send(sdi, &packet);
+		if (analog.meaning->mq != 0) {
+			/* Got a measurement. */
+			packet.type = SR_DF_ANALOG;
+			packet.payload = &analog;
+			sr_session_send(sdi, &packet);
+			sent_sample = TRUE;
+		}
+	}
+
+	if (sent_sample) {
 		sr_sw_limits_update_samples_read(&devc->limits, 1);
 	}
 }

src/hardware/serial-dmm/protocol.h

@@ -47,6 +47,8 @@ struct dmm_info {
 	int64_t req_delay_ms;
 	/** Packet request function. */
 	int (*packet_request)(struct sr_serial_dev_inst *);
+	/** Number of channels / displays. */
+	size_t channel_count;
 	/** Packet validation function. */
 	gboolean (*packet_valid)(const uint8_t *);
 	/** Packet parsing function. */

src/libsigrok-internal.h

@@ -1273,6 +1273,7 @@ SR_PRIV int sr_m2110_parse(const uint8_t *buf, float *floatval,
 #define METEX14_PACKET_SIZE 14
 
 struct metex14_info {
+	size_t ch_idx;
 	gboolean is_ac, is_dc, is_resistance, is_capacity, is_temperature;
 	gboolean is_diode, is_frequency, is_ampere, is_volt, is_farad;
 	gboolean is_hertz, is_ohm, is_celsius, is_pico, is_nano, is_micro;
@@ -1286,6 +1287,9 @@ SR_PRIV int sr_metex14_packet_request(struct sr_serial_dev_inst *serial);
 SR_PRIV gboolean sr_metex14_packet_valid(const uint8_t *buf);
 SR_PRIV int sr_metex14_parse(const uint8_t *buf, float *floatval,
 			     struct sr_datafeed_analog *analog, void *info);
+SR_PRIV gboolean sr_metex14_4packets_valid(const uint8_t *buf);
+SR_PRIV int sr_metex14_4packets_parse(const uint8_t *buf, float *floatval,
+			     struct sr_datafeed_analog *analog, void *info);
 
 /*--- hardware/dmm/rs9lcd.c -------------------------------------------------*/