From: Matthias Heidbrink <redacted>
Date: Thu, 21 Nov 2013 14:47:09 +0000 (+0100)
Subject: gmc_mh_1x_2x: Completed driver for Metrahit 1x/2x
X-Git-Tag: libsigrok-0.3.0~541
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=f57924179d08dee9d24099233ffbee2123613a22;p=libsigrok.git

gmc_mh_1x_2x: Completed driver for Metrahit 1x/2x

This driver supports devices with “RS232“ interface (Metrahit 16I,
18S, Siemens B1105 tested, 29S incomplete).
---

diff --git a/hardware/gmc-mh-1x-2x/api.c b/hardware/gmc-mh-1x-2x/api.c
index 8647d7fa..42969412 100644
--- a/hardware/gmc-mh-1x-2x/api.c
+++ b/hardware/gmc-mh-1x-2x/api.c
@@ -17,48 +17,215 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <string.h>
+
 #include "protocol.h"
 
+/* Serial communication parameters for Metrahit 1x/2x with 'RS232' adaptor */
+#define SERIALCOMM_1X_RS232 "8228/6n1/dtr=1/rts=1/flow=0" /* =8192, closer with divider */
+#define SERIALCOMM_2X_RS232 "9600/6n1/dtr=1/rts=1/flow=0"
+#define VENDOR_GMC "Gossen Metrawatt"
+
 SR_PRIV struct sr_dev_driver gmc_mh_1x_2x_rs232_driver_info;
-static struct sr_dev_driver *di = &gmc_mh_1x_2x_rs232_driver_info;
 
-static int init(struct sr_context *sr_ctx)
+static const int32_t hwopts[] = {
+	SR_CONF_CONN,
+	SR_CONF_SERIALCOMM,
+};
+
+static const int32_t hwcaps[] = {
+	SR_CONF_MULTIMETER,
+	SR_CONF_LIMIT_SAMPLES,
+	SR_CONF_LIMIT_MSEC,
+	SR_CONF_CONTINUOUS,
+};
+
+/** Driver init function */
+static int init_1x_2x_rs232(struct sr_context *sr_ctx)
 {
-	return std_init(sr_ctx, di, LOG_PREFIX);
+	return std_init(sr_ctx, &gmc_mh_1x_2x_rs232_driver_info, LOG_PREFIX);
 }
 
-static GSList *scan(GSList *options)
+
+/** Read single byte from serial port.
+ *  \retval -1 Timeout or error.
+ *  \retval other Byte.
+ */
+static int read_byte(struct sr_serial_dev_inst *serial, gint64 timeout)
 {
-	struct drv_context *drvc;
-	GSList *devices;
+	guint8 result = 0;
+	int rc = 0;
+
+	for (;;) {
+		rc = serial_read(serial, &result, 1);
+		if (rc == 1) {
+			sr_spew("read: 0x%02x/%d", result, result);
+			return result;
+		}
+		if (g_get_monotonic_time() > timeout)
+			return -1;
+		g_usleep(2000);
+	}
+}
+
+/** Try to detect GMC 1x/2x multimeter model in send mode for max. 1 second.
+ *  \param serial Configured, open serial port.
+ *
+ *  \retval NULL Detection failed.
+ *  \retval other Model code.
+ */
+static enum model scan_model_sm(struct sr_serial_dev_inst *serial)
+{
+	int byte, bytecnt, cnt;
+	enum model model;
+	gint64 timeout_us;
+
+	model = SR_METRAHIT_NONE;
+	timeout_us = g_get_monotonic_time() + 1*1000*1000;
+
+	/* Try to find message consisting of device code and several
+	 * (at least 4) data bytes. */
+	for (bytecnt = 0; bytecnt < 100; bytecnt++) {
+		byte = read_byte(serial, timeout_us);
+		if ((byte == -1) || (timeout_us < g_get_monotonic_time()))
+			break;
+		if ((byte & MSGID_MASK) == MSGID_INF) {
+			if (!(model = sr_gmc_decode_model_sm(byte & MSGC_MASK)))
+				break;
+			/* Now expect (at least) 4 data bytes */
+			for (cnt = 0; cnt < 4; cnt++) {
+				byte = read_byte(serial, timeout_us);
+				if ((byte == -1) ||
+					((byte & MSGID_MASK) != MSGID_DATA))
+				{
+					model = SR_METRAHIT_NONE;
+					bytecnt = 100;
+					break;
+				}
+			}
+			break;
+		}
+	}
 
-	(void)options;
+	return model;
+}
+
+/** Scan for Metrahit 1x and Metrahit 2x in send mode using Gossen Metrawatt
+ *  'RS232' interface. The older 1x models use 8192 and the newer 2x 9600 baud.
+ *  The DMM usually sends up to about 20 messages per second. However, depending
+ *  on configuration and measurement mode the intervals can be much larger and
+ *  then the detection might not work.
+ */
+static GSList *scan_1x_2x_rs232(GSList *options)
+{
+	struct sr_dev_inst *sdi;
+	struct drv_context *drvc;
+	struct dev_context *devc;
+	struct sr_config *src;
+	struct sr_probe *probe;
+	struct sr_serial_dev_inst *serial;
+	GSList *l, *devices;
+	const char *conn, *serialcomm;
+	enum model model;
+	gboolean serialcomm_given;
+	int cnt;
 
 	devices = NULL;
-	drvc = di->priv;
+	drvc = (&gmc_mh_1x_2x_rs232_driver_info)->priv;
 	drvc->instances = NULL;
+	conn = serialcomm = NULL;
+	model = SR_METRAHIT_NONE;
+	serialcomm_given = FALSE;
+
+	sr_spew("scan_1x_2x_rs232() called!");
+
+	for (l = options; l; l = l->next) {
+		src = l->data;
+		switch (src->key) {
+		case SR_CONF_CONN:
+			conn = g_variant_get_string(src->data, NULL);
+			break;
+		case SR_CONF_SERIALCOMM:
+			serialcomm = g_variant_get_string(src->data, NULL);
+			serialcomm_given = TRUE;
+			break;
+		}
+	}
+	if (!conn)
+		return NULL;
+	if (!serialcomm)
+		serialcomm = SERIALCOMM_2X_RS232;
+
+	if (!(serial = sr_serial_dev_inst_new(conn, serialcomm)))
+		return NULL;
+
+	if (serial_open(serial, SERIAL_RDWR | SERIAL_NONBLOCK) != SR_OK) {
+		sr_serial_dev_inst_free(serial);
+		return NULL;
+	}
 
-	/* TODO: scan for devices, either based on a SR_CONF_CONN option
-	 * or on a USB scan. */
+	serial_flush(serial);
+
+	model = scan_model_sm(serial);
+
+	/* If detection failed and no user-supplied parameters,
+	 * try second baud rate. */
+	if ((model == SR_METRAHIT_NONE) && !serialcomm_given) {
+		serialcomm = SERIALCOMM_1X_RS232;
+		g_free(serial->serialcomm);
+		serial->serialcomm = g_strdup(serialcomm);
+		if (serial_set_paramstr(serial, serialcomm) == SR_OK) {
+			serial_flush(serial);
+			model = scan_model_sm(serial);
+		}
+	}
+
+	if (model != SR_METRAHIT_NONE) {
+		sr_spew("%s %s detected!", VENDOR_GMC, sr_gmc_model_str(model));
+		if (!(sdi = sr_dev_inst_new(0, SR_ST_INACTIVE, VENDOR_GMC,
+				sr_gmc_model_str(model), "")))
+			return NULL;
+		if (!(devc = g_try_malloc0(sizeof(struct dev_context)))) {
+			sr_err("Device context malloc failed.");
+			return NULL;
+		}
+		devc->model = model;
+		devc->limit_samples = 0;
+		devc->limit_msec = 0;
+		devc->num_samples = 0;
+		devc->elapsed_msec = g_timer_new();
+		devc->settings_ok = FALSE;
+
+		sdi->conn = serial;
+		sdi->priv = devc;
+		sdi->driver = &gmc_mh_1x_2x_rs232_driver_info;
+		if (!(probe = sr_probe_new(0, SR_PROBE_ANALOG, TRUE, "P1")))
+			return NULL;
+		sdi->probes = g_slist_append(sdi->probes, probe);
+		drvc->instances = g_slist_append(drvc->instances, sdi);
+		devices = g_slist_append(devices, sdi);
+	}
 
 	return devices;
 }
 
-static GSList *dev_list(void)
+/** Driver device list function */
+static GSList *dev_list_1x_2x_rs232(void)
 {
-	return ((struct drv_context *)(di->priv))->instances;
+	return ((struct drv_context *)(gmc_mh_1x_2x_rs232_driver_info.priv))
+			->instances;
 }
 
-static int dev_clear(void)
+static int dev_clear_1x_2x_rs232(void)
 {
-	return std_dev_clear(di, NULL);
+	return std_dev_clear(&gmc_mh_1x_2x_rs232_driver_info, NULL);
 }
 
 static int dev_open(struct sr_dev_inst *sdi)
 {
-	(void)sdi;
-
-	/* TODO: get handle from sdi->conn and open it. */
+	struct sr_serial_dev_inst *serial = sdi->conn;
+	if (serial_open(serial, SERIAL_RDWR | SERIAL_NONBLOCK) != SR_OK)
+		return SR_ERR;
 
 	sdi->status = SR_ST_ACTIVE;
 
@@ -67,24 +234,33 @@ static int dev_open(struct sr_dev_inst *sdi)
 
 static int dev_close(struct sr_dev_inst *sdi)
 {
-	(void)sdi;
+	struct sr_serial_dev_inst *serial;
+	struct dev_context *devc;
 
-	/* TODO: get handle from sdi->conn and close it. */
+	serial = sdi->conn;
+	if (serial && serial->fd != -1) {
+		serial_close(serial);
+		sdi->status = SR_ST_INACTIVE;
+	}
 
 	sdi->status = SR_ST_INACTIVE;
 
+	/* Free dynamically allocated resources. */
+	if ((devc = sdi->priv) && devc->elapsed_msec) {
+		g_timer_destroy(devc->elapsed_msec);
+		devc->elapsed_msec = NULL;
+		devc->model = SR_METRAHIT_NONE;
+	}
+
 	return SR_OK;
 }
 
-static int cleanup(void)
+static int cleanup_sm_rs232(void)
 {
-	dev_clear();
-
-	/* TODO: free other driver resources, if any. */
-
-	return SR_OK;
+	return dev_clear_1x_2x_rs232();
 }
 
+/** TODO */
 static int config_get(int key, GVariant **data, const struct sr_dev_inst *sdi,
 		const struct sr_probe_group *probe_group)
 {
@@ -107,68 +283,102 @@ static int config_get(int key, GVariant **data, const struct sr_dev_inst *sdi,
 static int config_set(int key, GVariant *data, const struct sr_dev_inst *sdi,
 		const struct sr_probe_group *probe_group)
 {
-	int ret;
+	struct dev_context *devc;
 
-	(void)data;
 	(void)probe_group;
 
 	if (sdi->status != SR_ST_ACTIVE)
 		return SR_ERR_DEV_CLOSED;
 
-	ret = SR_OK;
+	if (!(devc = sdi->priv)) {
+		sr_err("sdi->priv was NULL.");
+		return SR_ERR_BUG;
+	}
+
 	switch (key) {
-	/* TODO */
+	case SR_CONF_LIMIT_MSEC:
+		if (g_variant_get_uint64(data) == 0) {
+			sr_err("LIMIT_MSEC can't be 0.");
+			return SR_ERR;
+		}
+		devc->limit_msec = g_variant_get_uint64(data);
+		sr_dbg("Setting time limit to %" PRIu64 "ms.",
+		       devc->limit_msec);
+		break;
+	case SR_CONF_LIMIT_SAMPLES:
+		devc->limit_samples = g_variant_get_uint64(data);
+		sr_dbg("Setting sample limit to %" PRIu64 ".",
+		       devc->limit_samples);
+		break;
 	default:
-		ret = SR_ERR_NA;
+		return SR_ERR_NA;
 	}
 
-	return ret;
+	return SR_OK;
 }
 
 static int config_list(int key, GVariant **data, const struct sr_dev_inst *sdi,
 		const struct sr_probe_group *probe_group)
 {
-	int ret;
-
 	(void)sdi;
-	(void)data;
-	(void)probe_group;
 
-	ret = SR_OK;
 	switch (key) {
-	/* TODO */
+	case SR_CONF_SCAN_OPTIONS:
+		*data = g_variant_new_fixed_array(G_VARIANT_TYPE_INT32,
+				hwopts, ARRAY_SIZE(hwopts), sizeof(int32_t));
+		break;
+	case SR_CONF_DEVICE_OPTIONS:
+		*data = g_variant_new_fixed_array(G_VARIANT_TYPE_INT32,
+				hwcaps, ARRAY_SIZE(hwcaps), sizeof(int32_t));
+		break;
 	default:
 		return SR_ERR_NA;
 	}
 
-	return ret;
+	return SR_OK;
 }
 
-static int dev_acquisition_start(const struct sr_dev_inst *sdi,
+static int dev_acq_start_1x_2x_rs232(const struct sr_dev_inst *sdi,
 				    void *cb_data)
 {
-	(void)sdi;
-	(void)cb_data;
+	struct dev_context *devc;
+	struct sr_serial_dev_inst *serial;
+
+	if (!sdi || !cb_data || !(devc = sdi->priv))
+		return SR_ERR_BUG;
 
 	if (sdi->status != SR_ST_ACTIVE)
 		return SR_ERR_DEV_CLOSED;
 
-	/* TODO: configure hardware, reset acquisition state, set up
-	 * callbacks and send header packet. */
+	devc->cb_data = cb_data;
+	devc->settings_ok = FALSE;
+	devc->buflen = 0;
+
+	/* Send header packet to the session bus. */
+	std_session_send_df_header(cb_data, LOG_PREFIX);
+
+	/* Start timer, if required. */
+	if (devc->limit_msec)
+		g_timer_start(devc->elapsed_msec);
+
+	/* Poll every 40ms, or whenever some data comes in. */
+	serial = sdi->conn;
+	sr_source_add(serial->fd, G_IO_IN, 40, gmc_mh_1x_2x_receive_data,
+		(void *)sdi);
 
 	return SR_OK;
 }
 
-static int dev_acquisition_stop(struct sr_dev_inst *sdi, void *cb_data)
+static int dev_acq_stop(struct sr_dev_inst *sdi, void *cb_data)
 {
-	(void)cb_data;
+	struct dev_context *devc;
 
-	if (sdi->status != SR_ST_ACTIVE)
-		return SR_ERR_DEV_CLOSED;
+	/* Stop timer, if required. */
+	if (sdi && (devc = sdi->priv) && devc->limit_msec)
+		g_timer_stop(devc->elapsed_msec);
 
-	/* TODO: stop acquisition. */
-
-	return SR_OK;
+	return std_dev_acquisition_stop_serial(sdi, cb_data, dev_close,
+			sdi->conn, LOG_PREFIX);
 }
 
 SR_PRIV struct sr_dev_driver gmc_mh_1x_2x_rs232_driver_info = {
@@ -176,17 +386,17 @@ SR_PRIV struct sr_dev_driver gmc_mh_1x_2x_rs232_driver_info = {
 	.longname =
 		"Gossen Metrawatt Metrahit 1x/2x DMMs, 'RS232' Interface",
 	.api_version = 1,
-	.init = init,
-	.cleanup = cleanup,
-	.scan = scan,
-	.dev_list = dev_list,
-	.dev_clear = dev_clear,
+	.init = init_1x_2x_rs232,
+	.cleanup = cleanup_sm_rs232,
+	.scan = scan_1x_2x_rs232,
+	.dev_list = dev_list_1x_2x_rs232,
+	.dev_clear = dev_clear_1x_2x_rs232,
 	.config_get = config_get,
 	.config_set = config_set,
 	.config_list = config_list,
 	.dev_open = dev_open,
 	.dev_close = dev_close,
-	.dev_acquisition_start = dev_acquisition_start,
-	.dev_acquisition_stop = dev_acquisition_stop,
+	.dev_acquisition_start = dev_acq_start_1x_2x_rs232,
+	.dev_acquisition_stop = dev_acq_stop,
 	.priv = NULL,
 };
diff --git a/hardware/gmc-mh-1x-2x/protocol.c b/hardware/gmc-mh-1x-2x/protocol.c
index ef7427fe..0583b2b2 100644
--- a/hardware/gmc-mh-1x-2x/protocol.c
+++ b/hardware/gmc-mh-1x-2x/protocol.c
@@ -17,12 +17,762 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <math.h>
+#include <string.h>
+
 #include "protocol.h"
 
+/** Set or clear flags in devc->mqflags. */
+static void setmqf(struct dev_context *devc, uint64_t flags, gboolean set)
+{
+	if (set)
+		devc->mqflags |= flags;
+	else
+		devc->mqflags &= ~flags;
+}
+
+/** Decode current type and measured value, Metrahit 12-16.
+ */
+static void decode_ctmv_16(guchar ctmv, struct dev_context *devc)
+{
+	devc->mq = 0;
+	devc->unit = 0;
+	devc->mqflags = 0;
+
+	switch (ctmv) {
+	case 0x00: /* 0000 - */
+		break;
+	case 0x01: /* 0001 mV DC */
+		devc->scale1000 = -1; /* Fall through */
+	case 0x02: /* 0010 V DC */
+	case 0x03: /* 0011 V AC+DC */
+	case 0x04: /* 0100 V AC */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		if (ctmv <= 0x03)
+			devc->mqflags |= SR_MQFLAG_DC;
+		if (ctmv >= 0x03) {
+			devc->mqflags |= SR_MQFLAG_AC;
+			if (devc->model >= SR_METRAHIT_16S)
+				devc->mqflags |= SR_MQFLAG_RMS;
+			}
+		break;
+	case 0x05: /* 0101 Hz (15S/16S only) */
+	case 0x06: /* 0110 kHz (15S/16S only) */
+		devc->mq = SR_MQ_FREQUENCY;
+		devc->unit = SR_UNIT_HERTZ;
+		if (ctmv == 0x06)
+			devc->scale1000 = 1;
+		break;
+	case 0x07: /* 0111 % (15S/16S only) */
+		devc->mq = SR_MQ_DUTY_CYCLE;
+		devc->unit = SR_UNIT_PERCENTAGE;
+		break;
+	case 0x08: /* 1000 Diode */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		devc->mqflags |= SR_MQFLAG_DIODE;
+		break;
+	case 0x09: /* 1001 Ohm, °C */
+	case 0x0a: /* 1010 kOhm */
+	case 0x0b: /* 1011 MOhm */
+		devc->mq = SR_MQ_RESISTANCE; /* Changed to temp. later if req.*/
+		devc->unit = SR_UNIT_OHM;
+		devc->scale1000 = ctmv - 0x09;
+		break;
+	case 0x0c: /* 1100 nF (15S/16S only) */
+	case 0x0d: /* 1101 µF (15S/16S only) */
+		devc->mq = SR_MQ_CAPACITANCE;
+		devc->unit = SR_UNIT_FARAD;
+		if (ctmv == 0x0c)
+			devc->scale1000 = -3;
+		else
+			devc->scale1000 = -2;
+		break;
+	case 0x0e: /* mA, µA */
+		devc->scale1000 = -1; /* Fall through. */
+	case 0x0f: /* A */
+		devc->mq = SR_MQ_CURRENT;
+		devc->unit = SR_UNIT_AMPERE;
+		if (devc->model == SR_METRAHIT_16S)
+			devc->mqflags |= SR_MQFLAG_RMS;
+		/* 16I A only with clamp, RMS questionable. */
+		break;
+	}
+}
+
+/** Decode range/sign/acdc byte special chars (Metrahit 12-16).
+ *  \param[in] spc Special characters 1 and 2 (s1 | (s2<<4)).
+ */
+static void decode_rs_16(guchar rs, struct dev_context *devc)
+{
+	sr_spew("decode_rs_16(%d) scale = %f", rs, devc->scale);
+
+	if (rs & 0x08) /* Sign */
+		devc->scale *= -1.0;
+
+	if (devc->mq == SR_MQ_CURRENT) {
+		if (rs & 0x04) /* Current is AC */
+			devc->mqflags |= SR_MQFLAG_AC;
+		else
+			devc->mqflags |= SR_MQFLAG_DC;
+	}
+
+	switch (rs & 0x03) {
+	case 0:
+		if (devc->mq == SR_MQ_VOLTAGE)  /* V */
+			devc->scale *= 0.1;
+		else if (devc->mq == SR_MQ_CURRENT) /* 000.0 µA */
+			devc->scale *= 0.0000001; /* Untested! */
+		else if (devc->mq == SR_MQ_RESISTANCE) {
+			if (devc->buflen >= 10) {
+				/* °C with 10 byte msg type, otherwise GOhm. */
+				devc->mq = SR_MQ_TEMPERATURE;
+				devc->unit = SR_UNIT_CELSIUS;
+				devc->scale *= 0.01;
+			}
+			else if ((devc->scale1000 == 2)) {
+				/* 16I Iso 500/1000V 3 GOhm */
+				devc->scale *= 0.1;
+			}
+		}
+		break;
+	case 1:
+		devc->scale *= 0.0001;
+		break;
+	case 2:
+		devc->scale *= 0.001;
+		break;
+	case 3:
+		devc->scale *= 0.01;
+		break;
+	}
+}
+
+/** Decode special chars, Metrahit 12-16.
+ *  \param[in] spc Special characters 1 and 2 (s1 | (s2<<4)).
+ */
+static void decode_spc_16(guchar spc, struct dev_context *devc)
+{
+	/* xxxx1xxx ON */
+	/* TODO: What does that mean? Power on? The 16I sets this. */
+	/* xxxxx1xx BEEP */
+	/* xxxxxx1x Low battery */
+	/* xxxxxxx1 FUSE */
+	/* 1xxxxxxx MIN */
+	setmqf(devc, SR_MQFLAG_MIN, spc & 0x80);
+
+	/* x1xxxxxx MAN */
+	setmqf(devc, SR_MQFLAG_AUTORANGE, !(spc & 0x40));
+
+	/* xx1xxxxx DATA */
+	setmqf(devc, SR_MQFLAG_HOLD, spc & 0x20);
+
+	/* xxx1xxxx MAX */
+	setmqf(devc, SR_MQFLAG_MAX, spc & 0x10);
+}
+
+/** Decode current type and measured value, Metrahit 18.
+ */
+static void decode_ctmv_18(guchar ctmv, struct dev_context *devc)
+{
+	devc->mq = 0;
+	devc->unit = 0;
+	devc->mqflags = 0;
+
+	switch (ctmv) {
+	case 0x00: /* 0000 - */
+		break;
+	case 0x01: /* 0001 V AC */
+	case 0x02: /* 0010 V AC+DC */
+	case 0x03: /* 0011 V DC */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		if (ctmv <= 0x02)
+			devc->mqflags |= (SR_MQFLAG_AC | SR_MQFLAG_RMS);
+		if (ctmv >= 0x02)
+			devc->mqflags |= SR_MQFLAG_DC;
+		break;
+	case 0x04: /* 0100 Ohm/Ohm with buzzer */
+		devc->mq = SR_MQ_RESISTANCE;
+		devc->unit = SR_UNIT_OHM;
+		break;
+	case 0x05: /* 0101 Diode/Diode with buzzer*/
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		devc->mqflags |= SR_MQFLAG_DIODE;
+		break;
+	case 0x06: /* 0110 °C */
+		devc->mq = SR_MQ_TEMPERATURE;
+		devc->unit = SR_UNIT_CELSIUS;
+		break;
+	case 0x07: /* 0111 F */
+		devc->mq = SR_MQ_CAPACITANCE;
+		devc->unit = SR_UNIT_FARAD;
+		break;
+	case 0x08: /* 1000 mA DC */
+	case 0x09: /* 1001 A DC */
+	case 0x0a: /* 1010 mA AC+DC */
+	case 0x0b: /* 1011 A AC+DC */
+		devc->mq = SR_MQ_CURRENT;
+		devc->unit = SR_UNIT_AMPERE;
+		devc->mqflags |= SR_MQFLAG_DC;
+		if (ctmv >= 0x0a)
+			devc->mqflags |= (SR_MQFLAG_AC | SR_MQFLAG_RMS);
+		if ((ctmv == 0x08) || (ctmv == 0x0a))
+			devc->scale1000 = -1;
+		break;
+	case 0x0c: /* 1100 Hz */
+		devc->mq = SR_MQ_FREQUENCY;
+		devc->unit = SR_UNIT_HERTZ;
+		break;
+	case 0x0d: /* 1101 dB */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_DECIBEL_VOLT;
+		devc->mqflags |= SR_MQFLAG_AC; /* dB available for AC only */
+		break;
+	case 0x0e: /* 1110 Events AC, Events AC+DC. Actually delivers just
+				* current voltage via IR, nothing more. */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		devc->mqflags |= SR_MQFLAG_AC | SR_MQFLAG_DC | SR_MQFLAG_RMS;
+		break;
+	case 0x0f: /* 1111 Clock */
+		devc->mq = SR_MQ_TIME;
+		devc->unit = SR_UNIT_SECOND;
+		devc->mqflags |= SR_MQFLAG_DURATION;
+		break;
+	}
+}
+
+/** Decode range/sign/acdc byte special chars, Metrahit 18.
+ *  \param[in] rs Rance/sign byte
+ */
+static void decode_rs_18(guchar rs, struct dev_context *devc)
+{
+	int range;
+
+	/* Sign */
+	if (((devc->scale > 0) && (rs & 0x08)) ||
+		((devc->scale < 0) && !(rs & 0x08)))
+		devc->scale *= -1.0;
+
+	/* Range */
+	range = rs & 0x07;
+	switch (devc->mq) {
+	case SR_MQ_VOLTAGE:
+		if (devc->unit == SR_UNIT_DECIBEL_VOLT) {
+			devc->scale *= pow(10.0, -2);
+			/* When entering relative mode, the device switches
+			 * from 10 byte to 6 byte msg format. Unfortunately
+			 * it switches back to 10 byte when the second value
+			 * is measured, so that's not sufficient to
+			 * identify relative mode.
+			 */
+		}
+		else if (devc->vmains_29S)
+			devc->scale *= pow(10.0, range - 2);
+		else
+			devc->scale *= pow(10.0, range - 5);
+		break;
+	case SR_MQ_CURRENT:
+		if (devc->scale1000 == -1)
+			devc->scale *= pow(10.0, range - 5);
+		else
+			devc->scale *= pow(10.0, range - 4);
+		break;
+	case SR_MQ_RESISTANCE:
+		devc->scale *= pow(10.0, range - 2);
+		break;
+	case SR_MQ_FREQUENCY:
+		devc->scale *= pow(10.0, range - 3);
+		break;
+	case SR_MQ_TEMPERATURE:
+		devc->scale *= pow(10.0, range - 2);
+		break;
+	case SR_MQ_CAPACITANCE:
+		devc->scale *= pow(10.0, range - 14);
+		break;
+	/* TODO: 29S Mains measurements. */
+	}
+}
+
+/** Decode special chars, Metrahit 18.
+ *  \param[in] spc Special characters 1 and 2 (s1 | (s2<<4)).
+ */
+static void decode_spc_18(guchar spc, struct dev_context *devc)
+{
+	/* xxxx1xxx ZERO */
+	/* xxxxx1xx BEEP */
+	/* xxxxxx1x Low battery */
+	/* xxxxxxx1 Fuse */
+
+	if (devc->mq == SR_MQ_TIME) {
+		/* xxx1xxxx Clock running: 1; stop: 0 */
+		sr_spew("Clock running: %d", spc >> 4);
+	}
+	else {
+		/* 1xxxxxxx MAN */
+		setmqf(devc, SR_MQFLAG_AUTORANGE, !(spc & 0x80));
+
+		/* x1xxxxxx MIN */
+		setmqf(devc, SR_MQFLAG_MIN, spc & 0x40);
+
+		/* xx1xxxxx MAX */
+		setmqf(devc, SR_MQFLAG_MAX, spc & 0x20);
+
+		/* xxx1xxxx DATA */
+		setmqf(devc, SR_MQFLAG_HOLD, spc & 0x10);
+	}
+}
+
+/** Decode current type and measured value, Metrahit 2x.
+ *  \param[in]  ctmv	Current type and measured value (v1 | (v2<<4)).
+ */
+static void decode_ctmv_2x(guchar ctmv, struct dev_context *devc)
+{
+	if ((ctmv > 0x1c) || (!devc)) {
+		sr_err("decode_ct_mv_2x(%d): invalid param(s)!", ctmv);
+		return;
+	}
+
+	devc->mq = 0;
+	devc->unit = 0;
+	devc->mqflags = 0;
+
+	switch (ctmv) {
+	/* 00000 unused */
+	case 0x01: /* 00001 V DC */
+	case 0x02: /* 00010 V AC+DC */
+	case 0x03: /* 00011 V AC */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		if (ctmv <= 0x02)
+			devc->mqflags |= SR_MQFLAG_DC;
+		if (ctmv >= 0x02) {
+			devc->mqflags |= SR_MQFLAG_AC;
+			if (devc->model >= SR_METRAHIT_24S)
+				devc->model |= SR_MQFLAG_RMS;
+		}
+		break;
+	case 0x04: /* 00100 mA DC */
+	case 0x05: /* 00101 mA AC+DC */
+		devc->scale1000 = -1;
+	case 0x06: /* 00110 A DC */
+	case 0x07: /* 00111 A AC+DC */
+		devc->mq = SR_MQ_CURRENT;
+		devc->unit = SR_UNIT_AMPERE;
+		devc->mqflags |= SR_MQFLAG_DC;
+		if ((ctmv == 0x05) || (ctmv == 0x07)) {
+			devc->mqflags |= SR_MQFLAG_AC;
+			if (devc->model >= SR_METRAHIT_24S)
+				devc->mqflags |= SR_MQFLAG_RMS;
+		}
+		break;
+	case 0x08: /* 01000 Ohm */
+		devc->mq = SR_MQ_RESISTANCE;
+		devc->unit = SR_UNIT_OHM;
+		break;
+	case 0x09: /* 01001 F */
+		devc->mq = SR_MQ_CAPACITANCE;
+		devc->unit = SR_UNIT_FARAD;
+		devc->scale *= 0.1;
+		break;
+	case 0x0a: /* 01010 dB */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_DECIBEL_VOLT;
+		devc->mqflags |= SR_MQFLAG_AC;
+		break;
+	case 0x0b: /* 01011 Hz U ACDC */
+	case 0x0c: /* 01100 Hz U AC */
+		devc->mq = SR_MQ_FREQUENCY;
+		devc->unit = SR_UNIT_HERTZ;
+		devc->mqflags |= SR_MQFLAG_AC;
+		if (ctmv <= 0x0b)
+			devc->mqflags |= SR_MQFLAG_DC;
+		break;
+	case 0x0d: /* 01101 W on power, mA range (29S only) */
+	case 0x0e: /* 01110 W on power, A range (29S only) */
+		/* TODO: Differences between Send Mode and bidir protocol here */
+		devc->mq = SR_MQ_POWER;
+		devc->unit = SR_UNIT_WATT;
+		break;
+	case 0x0f: /* 01111 Diode */
+	case 0x10: /* 10000 Diode with buzzer (actually cont. with voltage) */
+		devc->unit = SR_UNIT_VOLT;
+		if (ctmv == 0x0f) {
+			devc->mq = SR_MQ_VOLTAGE;
+			devc->mqflags |= SR_MQFLAG_DIODE;
+			devc->scale *= 0.1;
+		}
+		else {
+			devc->mq = SR_MQ_CONTINUITY;
+			devc->scale *= 0.00001;
+		}
+		devc->unit = SR_UNIT_VOLT;
+		break;
+	case 0x11: /* 10001 Ohm with buzzer */
+		devc->mq = SR_MQ_CONTINUITY;
+		devc->unit = SR_UNIT_OHM;
+		devc->scale1000 = -1;
+		break;
+	case 0x12: /* 10010 Temperature */
+		devc->mq = SR_MQ_TEMPERATURE;
+		devc->unit = SR_UNIT_CELSIUS;
+		/* This can be Fahrenheit. That is detected by range=4 later. */
+		break;
+	/* 0x13 10011, 0x14 10100 unsed */
+	case 0x15: /* 10101 Press (29S only) */
+		/* TODO: What does that mean? Possibly phase shift?
+		   Then we need a unit/flag for it. */
+		devc->mq = SR_MQ_GAIN;
+		devc->unit = SR_UNIT_PERCENTAGE;
+		break;
+	case 0x16: /* 10110 Pulse W (29S only) */
+		/* TODO: Own unit and flag for this! */
+		devc->mq = SR_MQ_POWER;
+		devc->unit = SR_UNIT_WATT;
+		break;
+	case 0x17: /* 10111 TRMS V on mains (29S only) */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_VOLT;
+		devc->mqflags |= (SR_MQFLAG_AC | SR_MQFLAG_RMS);
+		devc->vmains_29S = TRUE;
+		break;
+	case 0x18: /* 11000 Counter (zero crossings of a signal) */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_UNITLESS;
+		break;
+	case 0x19: /* 11001 Events U ACDC */
+	case 0x1a: /* 11010 Events U AC */
+		/* TODO: No unit or flags for this yet! */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_UNITLESS;
+		devc->mqflags |= SR_MQFLAG_AC;
+		if (ctmv <= 0x19)
+			devc->mqflags |= SR_MQFLAG_DC;
+		break;
+	case 0x1b: /* 11011 pulse on mains (29S only) */
+		/* TODO: No unit or flags for this yet! */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_UNITLESS;
+		devc->mqflags |= SR_MQFLAG_AC;
+		break;
+	case 0x1c: /* 11100 dropout on mains (29S only) */
+		/* TODO: No unit or flags for this yet! */
+		devc->mq = SR_MQ_VOLTAGE;
+		devc->unit = SR_UNIT_UNITLESS;
+		devc->mqflags |= SR_MQFLAG_AC;
+		break;
+	default:
+		sr_err("decode_ctmv_2x(%d, ...): Unknown ctmv!");
+	}
+}
+
+/** Decode range/sign/acdc byte special chars, Metrahit 2x.
+ *  \param[in] rs Rance/sign byte
+ */
+static void decode_rs_2x(guchar rs, struct dev_context *devc)
+{
+			int range;
+
+	/* Sign */
+	if (((devc->scale > 0) && (rs & 0x08)) ||
+		((devc->scale < 0) && !(rs & 0x08)))
+		devc->scale *= -1.0;
+
+	/* Range */
+	range = rs & 0x07;
+	switch (devc->mq) {
+	case SR_MQ_VOLTAGE:
+		if (devc->unit == SR_UNIT_DECIBEL_VOLT) {
+			devc->scale *= pow(10.0, -3);
+		}
+		else if (devc->vmains_29S)
+			devc->scale *= pow(10.0, range - 2);
+		else if(devc->mqflags & SR_MQFLAG_AC)
+			devc->scale *= pow(10.0, range - 6);
+		else /* "Undocumented feature": Between AC and DC
+			scaling differs by 1. */
+			devc->scale *= pow(10.0, range - 5);
+		break;
+	case SR_MQ_CURRENT:
+		if (devc->scale1000 == -1)
+			devc->scale *= pow(10.0, range - 5);
+		else
+			devc->scale *= pow(10.0, range - 4);
+		break;
+	case SR_MQ_RESISTANCE:
+		devc->scale *= pow(10.0, range - 3);
+		break;
+	case SR_MQ_FREQUENCY:
+		devc->scale *= pow(10.0, range - 3);
+		break;
+	case SR_MQ_TEMPERATURE:
+		if (range == 4) { /* Indicator for °F */
+			devc->unit = SR_UNIT_FAHRENHEIT;
+		}
+
+		devc->scale *= pow(10.0, - 2);
+		break;
+	case SR_MQ_CAPACITANCE:
+		devc->scale *= pow(10.0, range - 13);
+		break;
+	/* TODO: 29S Mains measurements. */
+	}
+}
+
+/** Decode special chars (Metrahit 2x).
+ *  \param[in] spc Special characters 1 and 2 (s1 | (s2<<4)).
+ */
+static void decode_spc_2x(guchar spc, struct dev_context *devc)
+{
+	/* xxxxxxx1 Fuse */
+
+	/* xxxxxx1x Low battery */
+
+	/* xxxxx1xx BEEP */
+
+	/* xxxx1xxx ZERO */
+
+	/* xxx1xxxx DATA */
+	setmqf(devc, SR_MQFLAG_HOLD, spc & 0x10);
+
+	/* x11xxxxx unused */
+	/* 1xxxxxxx MAN */
+	setmqf(devc, SR_MQFLAG_AUTORANGE, !(spc & 0x80));
+}
+
+/** Clean range and sign. */
+static void clean_rs_v(struct dev_context *devc)
+{
+	devc->value = 0.0;
+	devc->scale = 1.0;
+}
+
+/** Clean current type, measured variable, range and sign. */
+static void clean_ctmv_rs_v(struct dev_context *devc)
+{
+	devc->mq = 0;
+	devc->unit = 0;
+	devc->mqflags = 0;
+	devc->scale1000 = 0;
+	devc->vmains_29S = FALSE;
+	clean_rs_v(devc);
+}
+
+/** Send prepared value. */
+static void send_value(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	struct sr_datafeed_analog analog;
+	struct sr_datafeed_packet packet;
+
+	devc = sdi->priv;
+
+	memset(&analog, 0, sizeof(analog));
+	analog.probes = sdi->probes;
+	analog.num_samples = 1;
+	analog.mq = devc->mq;
+	analog.unit = devc->unit;
+	analog.mqflags = devc->mqflags;
+	analog.data = &devc->value;
+
+	memset(&packet, 0, sizeof(packet));
+	packet.type = SR_DF_ANALOG;
+	packet.payload = &analog;
+	sr_session_send(devc->cb_data, &packet);
+
+	devc->num_samples++;
+}
+
+/** Process 6-byte data message, Metrahit 1x/2x. */
+static void process_msg_dta_6(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	int cnt;
+	guchar dgt;
+
+	devc = sdi->priv;
+	clean_rs_v(devc);
+
+	/* Byte 0, range and sign */
+	if (devc->model <= SR_METRAHIT_16X) {
+		decode_rs_16(bc(devc->buf[0]), devc);
+	}
+	else if (devc->model < SR_METRAHIT_2X){
+		decode_rs_18(bc(devc->buf[0]), devc);
+	} else {
+		decode_rs_2x(bc(devc->buf[0]), devc);
+	}
+
+	/* Bytes 1-5, digits (ls first). */
+	for (cnt = 0; cnt < 5; cnt++) {
+		dgt = bc(devc->buf[1 + cnt]);
+		if (dgt >= 10) {
+			/* 10 Overload; on model <= 16X also 11 possible. */
+			devc->value = NAN;
+			devc->scale = 1.0;
+			break;
+		}
+		devc->value += pow(10.0, cnt) * dgt;
+	}
+	sr_spew("process_msg_dta_6() value=%f scale=%f scalet=%d",
+		devc->value, devc->scale, devc->scale1000);
+	if (devc->value != NAN)
+		devc->value *= devc->scale * pow(1000.0, devc->scale1000);
+
+	/* Create and send packet. */
+	send_value(sdi);
+}
+
+/** Process 5-byte info message, Metrahit 1x/2x. */
+static void process_msg_inf_5(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	enum model model;
+
+	devc = sdi->priv;
+
+	clean_ctmv_rs_v(devc);
+
+	/* Process byte 0 */
+	model = sr_gmc_decode_model_sm(bc(devc->buf[0]));
+	if (model != devc->model) {
+		sr_warn("Model mismatch in data: Detected %s, now %s",
+			sr_gmc_model_str(devc->model),
+			sr_gmc_model_str(model));
+	}
+
+	/* Process bytes 1-4 */
+	if (devc->model <= SR_METRAHIT_16X) {
+		decode_ctmv_16(bc(devc->buf[1]), devc);
+		decode_spc_16(bc(devc->buf[2]) | (bc(devc->buf[3]) << 4), devc);
+		decode_rs_16(bc(devc->buf[4]), devc);
+	}
+	else if (devc->model <= SR_METRAHIT_18S) {
+		decode_ctmv_18(bc(devc->buf[1]), devc);
+		decode_spc_18(bc(devc->buf[2]) | (bc(devc->buf[3]) << 4), devc);
+		decode_rs_18(bc(devc->buf[4]), devc);
+	}
+	else { /* Must be Metrahit 2x */
+		decode_ctmv_2x(bc(devc->buf[1]), devc);
+		decode_spc_2x(bc(devc->buf[2]) | (bc(devc->buf[3]) << 4), devc);
+		decode_rs_2x(bc(devc->buf[4]), devc);
+	}
+}
+
+/** Process 10-byte info/data message, Metrahit 15+. */
+static void process_msg_inf_10(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	int cnt;
+	guchar dgt;
+
+	devc = sdi->priv;
+
+	process_msg_inf_5(sdi);
+
+	/* Now decode numbers */
+	for (cnt = 0; cnt < 5; cnt++) {
+		dgt = bc(devc->buf[5 + cnt]);
+		if (dgt >= 10) { /* Overload */
+			devc->value = NAN;
+			devc->scale = 1.0;
+			break;
+		}
+		devc->value += pow(10.0, cnt) * dgt;
+	}
+	sr_spew("process_msg_inf_10() value=%f scale=%f scalet=%d",
+			devc->value, devc->scale,  devc->scale1000);
+
+	if (devc->value != NAN)
+		devc->value *= devc->scale * pow(1000.0, devc->scale1000);
+
+	/* Create and send packet. */
+	send_value(sdi);
+}
+
+/** Decode send interval (Metrahit 2x only). */
+static const char* decode_send_interval(guchar si)
+{
+	switch (si) {
+	case 0x00: return "0.05";
+	case 0x01: return "0.1";
+	case 0x02: return "0.2";
+	case 0x03: return "0.5";
+	case 0x04: return "00:01";
+	case 0x05: return "00:02";
+	case 0x06: return "00:05";
+	case 0x07: return "00:10";
+	case 0x08: return "00:20";
+	case 0x09: return "00:30";
+	case 0x0a: return "01:00";
+	case 0x0b: return "02:00";
+	case 0x0c: return "05:00";
+	case 0x0d: return "10:00";
+	case 0x0e: return "----";
+	case 0x0f: return "data";
+	default: return "Unknown value";
+	}
+}
+
+/** Process 13-byte info/data message, Metrahit 2x. */
+static void process_msg_inf_13(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	enum model model;
+	int cnt;
+	guchar dgt;
+
+	devc = sdi->priv;
+
+	clean_ctmv_rs_v(devc);
+
+	/* Byte 0, model. */
+	model = sr_gmc_decode_model_sm(bc(devc->buf[0]));
+	if (model != devc->model) {
+		sr_warn("Model mismatch in data: Detected %s, now %s",
+			sr_gmc_model_str(devc->model),
+			sr_gmc_model_str(model));
+	}
+
+	/* Bytes 1-4, 11. */
+	decode_ctmv_2x(bc(devc->buf[1]) | (bc(devc->buf[11]) << 4), devc);
+	decode_spc_2x(bc(devc->buf[2]) | (bc(devc->buf[3]) << 4), devc);
+	decode_rs_2x(bc(devc->buf[4]), devc);
+
+	/* Bytes 5-10, digits (ls first). */
+	for (cnt = 0; cnt < 6; cnt++) {
+		dgt = bc(devc->buf[5 + cnt]);
+		if (dgt == 10) { /* Overload */
+			devc->value = NAN;
+			devc->scale = 1.0;
+			break;
+		}
+		devc->value += pow(10.0, cnt) * dgt;
+	}
+	sr_spew("process_msg_inf_13() value=%f scale=%f scale1000=%d mq=%d "
+		"unit=%d mqflags=0x%02llx", devc->value, devc->scale,
+		devc->scale1000, devc->mq, devc->unit, devc->mqflags);
+	if (devc->value != NAN)
+		devc->value *= devc->scale * pow(1000.0, devc->scale1000);
+
+	/* Byte 12, Send Interval */
+	sr_spew("Send interval: %s", decode_send_interval(bc(devc->buf[12])));
+
+	/* Create and send packet. */
+	send_value(sdi);
+}
+
+
 SR_PRIV int gmc_mh_1x_2x_receive_data(int fd, int revents, void *cb_data)
 {
-	const struct sr_dev_inst *sdi;
+	struct sr_dev_inst *sdi;
 	struct dev_context *devc;
+	struct sr_serial_dev_inst *serial;
+	unsigned char buf, msgt;
+	int len;
 
 	(void)fd;
 
@@ -32,9 +782,180 @@ SR_PRIV int gmc_mh_1x_2x_receive_data(int fd, int revents, void *cb_data)
 	if (!(devc = sdi->priv))
 		return TRUE;
 
-	if (revents == G_IO_IN) {
-		/* TODO */
+	serial = sdi->conn;
+
+	if (revents == G_IO_IN) { /* Serial data arrived. */
+		while (GMC_BUFSIZE - devc->buflen - 1 > 0) {
+			len = serial_read(serial, devc->buf + devc->buflen, 1);
+			if (len < 1)
+				break;
+			buf = *(devc->buf + devc->buflen);
+			sr_spew("read 0x%02x/%d/%d", buf, buf, buf & MSGC_MASK);
+			devc->buflen += len;
+			if (!devc->settings_ok) {
+				/* If no device type/settings record processed
+				 * yet, wait for one. */
+				if ((devc->buf[0] & MSGID_MASK) != MSGID_INF) {
+					devc->buflen = 0;
+					continue;
+				}
+				devc->settings_ok = TRUE;
+			}
+
+			msgt = devc->buf[0] & MSGID_MASK;
+			switch (msgt) {
+			case MSGID_INF:
+				if (devc->buflen == 13) {
+					process_msg_inf_13(sdi);
+					devc->buflen = 0;
+					continue;
+				}
+				else if ((devc->buflen == 10) &&
+					 (devc->model <= SR_METRAHIT_18S)) {
+					process_msg_inf_10(sdi);
+					devc->buflen = 0;
+					continue;
+				}
+				else if ((devc->buflen >= 5) &&
+					(devc->buf[devc->buflen-1] &
+					MSGID_MASK) != MSGID_DATA) {
+					/* Char just received is beginning
+					 * of next message */
+					process_msg_inf_5(sdi);
+					devc->buf[0] =devc->buf[devc->buflen-1];
+					devc->buflen = 1;
+					continue;
+				}
+				break;
+			case MSGID_DTA:
+			case MSGID_D10:
+				if (devc->buflen == 6) {
+					process_msg_dta_6(sdi);
+					devc->buflen = 0;
+				}
+				break;
+			case MSGID_DATA:
+				sr_err("Comm error, unexpected data byte!");
+				devc->buflen = 0;
+				break;
+			}
+		}
+	}
+
+	/* If number of samples or time limit reached, stop aquisition. */
+	if (devc->limit_samples && (devc->num_samples >= devc->limit_samples)) {
+		sdi->driver->dev_acquisition_stop(sdi, cb_data);
+	}
+
+	if (devc->limit_msec) {
+		gdouble elapsed_s = g_timer_elapsed(devc->elapsed_msec, NULL);
+		if ((elapsed_s  * 1000) >= devc->limit_msec) {
+			sdi->driver->dev_acquisition_stop(sdi, cb_data);
+		}
 	}
 
 	return TRUE;
 }
+
+
+/** Decode model in "send mode" */
+SR_PRIV int sr_gmc_decode_model_sm(guchar mcode)
+{
+	if (mcode > 0xf) {
+		sr_err("decode_model(%d): Model code 0..15 expected!", mcode);
+		return SR_METRAHIT_NONE;
+	}
+
+	switch(mcode) {
+	case 0x04:  /* 0100b */
+		return SR_METRAHIT_12S;
+	case 0x08:  /* 1000b */
+		return SR_METRAHIT_13S14A;
+	case 0x09:  /* 1001b */
+		return SR_METRAHIT_14S;
+	case 0x0A:  /* 1010b */
+		return SR_METRAHIT_15S;
+	case 0x0B:  /* 1011b */
+		return SR_METRAHIT_16S;
+	case 0x06:  /* 0110b (undocumented by GMC!) */
+		return SR_METRAHIT_16I;
+	case 0x0D:  /* 1101b */
+		return SR_METRAHIT_18S;
+	case 0x02:  /* 0010b */
+		return SR_METRAHIT_22SM;
+	case 0x03:  /* 0011b */
+		return SR_METRAHIT_23S;
+	case 0x0f:  /* 1111b */
+		return SR_METRAHIT_24S;
+	case 0x05:  /* 0101b */
+		return SR_METRAHIT_25SM;
+	case 0x01:  /* 0001b */
+		return SR_METRAHIT_26S;
+	case 0x0c:  /* 1100b */
+		return SR_METRAHIT_28S;
+	case 0x0e:  /* 1110b */
+		return SR_METRAHIT_29S;
+	default:
+		sr_err("Unknown model code %d!", mcode);
+		return SR_METRAHIT_NONE;
+	}
+}
+
+/** Decode model in bidirectional mode.
+    \param[in] mcode Model code.
+
+    \return Model code
+*/
+SR_PRIV int sr_gmc_decode_model_bidi(guchar mcode)
+{
+	switch(mcode) {
+	case 2: return SR_METRAHIT_22SM;
+	case 3: return SR_METRAHIT_23S;
+	case 4: return SR_METRAHIT_24S;
+	case 5: return SR_METRAHIT_25SM;
+	case 1: return SR_METRAHIT_26S;
+	case 12: return SR_METRAHIT_28S;
+	case 14: return SR_METRAHIT_29S;
+	default:
+		sr_err("Unknown model code %d!", mcode);
+		return SR_METRAHIT_NONE;
+	}
+}
+
+SR_PRIV const char* sr_gmc_model_str(enum model mcode)
+{
+	switch (mcode) {
+	case SR_METRAHIT_NONE:
+		return "-uninitialized model variable-";
+	case SR_METRAHIT_12S:
+		return "METRAHit 12S";
+	case SR_METRAHIT_13S14A:
+		return "METRAHit 13S/14A";
+	case SR_METRAHIT_14S:
+		return "METRAHit 14S";
+	case SR_METRAHIT_15S:
+		return "METRAHit 15S";
+	case SR_METRAHIT_16S:
+		return "METRAHit 16S";
+	case SR_METRAHIT_16I:
+		return "METRAHit 16I";
+	case SR_METRAHIT_18S:
+		return "METRAHit 18S";
+	case SR_METRAHIT_22SM:
+		return "METRAHit 22S/M";
+	case SR_METRAHIT_23S:
+		return "METRAHit 23S";
+	case SR_METRAHIT_24S:
+		return "METRAHit 24S";
+	case SR_METRAHIT_25SM:
+		return "METRAHit 25S/M";
+	case SR_METRAHIT_26S:
+		return "METRAHit 26S";
+	case SR_METRAHIT_28S:
+		return "METRAHit 28S";
+	case SR_METRAHIT_29S:
+		return "METRAHit 29S";
+	default:
+		return "Unknown model code";
+	}
+}
diff --git a/hardware/gmc-mh-1x-2x/protocol.h b/hardware/gmc-mh-1x-2x/protocol.h
index 799421d0..711dd1c0 100644
--- a/hardware/gmc-mh-1x-2x/protocol.h
+++ b/hardware/gmc-mh-1x-2x/protocol.h
@@ -34,16 +34,99 @@
 #define sr_warn(s, args...) sr_warn(LOG_PREFIX s, ## args)
 #define sr_err(s, args...) sr_err(LOG_PREFIX s, ## args)
 
+#define GMC_BUFSIZE  266
+
+/** Message ID bits 4, 5 */
+#define MSGID_MASK 0x30	/**< Mask to get message ID bits */
+#define MSGID_INF  0x00 /**< Start of message with device info */
+#define MSGID_D10  0x10	/**< Start of data message, non-displayed intermediate */
+#define MSGID_DTA  0x20 /**< Start of data message, displayed, averaged */
+#define MSGID_DATA 0x30	/**< Data byte in message */
+
+#define MSGC_MASK 0x0f	/**< Mask to get message byte contents */
+
+#define MSGSRC_MASK 0xc0 /**< Mask to get bits related to message source */
+
+#define bc(x) (x & MSGC_MASK) /**< Get contents from a byte */
+
+#define MASK_6BITS 0x3f /**< Mask lower six bits. */
+
+/** Internal multimeter model codes. In opposite to the multimeter models from
+ *  protocol (see decode_model()), these codes allow working with ranges.
+ */
+enum model {
+	SR_METRAHIT_NONE	= 0,	/**< Value for uninitialized variable */
+	SR_METRAHIT_12S		= 12,
+	SR_METRAHIT_13S14A	= 13,
+	SR_METRAHIT_14S		= 14,
+	SR_METRAHIT_15S		= 15,
+	SR_METRAHIT_16S		= 16,
+	SR_METRAHIT_16I		= 17,
+	SR_METRAHIT_16X = SR_METRAHIT_16I,  /**< All Metrahit 16 */
+	/* A Metrahit 17 exists, but seems not to have an IR interface. */
+	SR_METRAHIT_18S		= 18,
+	SR_METRAHIT_2X		= 20,	/**< For model type comparisons */
+	SR_METRAHIT_22SM	= 22,
+	SR_METRAHIT_23S		= 23,
+	SR_METRAHIT_24S		= 24,
+	SR_METRAHIT_25SM	= 25,
+	SR_METRAHIT_26S		= 26,
+	SR_METRAHIT_28S		= 28,
+	SR_METRAHIT_29S		= 29,
+};
+
+/** Convert GMC model code in send mode to sigrok-internal one. */
+SR_PRIV int sr_gmc_decode_model_sm(guchar mcode);
+
+/** Convert GMC model code in bidirectional mode to sigrok-internal one.
+    \param[in] mcode Model code.
+
+    \return Model code
+*/
+SR_PRIV int sr_gmc_decode_model_bidi(guchar mcode);
+
+/** Create 14-bytes (42 byte) message used in bidirectional mode.
+ *  \param[in] addr Target address. 0..15, 0=Broadcast.
+ *  \param[in] func Function code.
+ *  \param[in] params Further parameters, &char[9]. Unused bytes must be 0.
+ *  \param[out] buf &guchar[42] Output buffer (3*14).
+ *
+ */
+void create_msg_14(guchar addr, guchar func, guchar* params, guchar* buf);
+
+/** Get model string from sigrok-internal model code.
+ */
+SR_PRIV const char* sr_gmc_model_str(enum model mcode);
+
 /** Private, per-device-instance driver context. */
 struct dev_context {
 	/* Model-specific information */
+	enum model model;	/**< Model code. */
 
 	/* Acquisition settings */
+	uint64_t limit_samples;	/**< Target number of samples */
+	uint64_t limit_msec;	/**< Target sampling time */
+
+	/* Opaque pointer passed in by frontend. */
+	void *cb_data;
 
 	/* Operational state */
+	gboolean settings_ok;	/**< Settings msg received yet. */
+	int msg_type;	/**< Message type (MSGID_INF, ...). */
+	int msg_len;	/**< Message lengh (valid when msg, curr. type known).*/
+	int mq;		/**< Measured quantity */
+	int unit;		/**< Measured unit */
+	uint64_t mqflags;	/**< Measured quantity flags */
+	float value;		/**< Measured value */
+	float scale;		/**< Scale for value. */
+	int8_t scale1000;   /**< Additional scale factor 1000^x. */
+	gboolean vmains_29S;	/**< Measured ctmv is V mains (29S only). */
 
 	/* Temporary state across callbacks */
-
+	uint64_t num_samples;	/**< Current #samples for limit_samples */
+	GTimer* elapsed_msec;	/**< Used for sampling with limit_msec  */
+	unsigned char buf[GMC_BUFSIZE];	/**< Buffer for read callback */
+	int buflen;			/**< Data len in buf */
 };
 
 SR_PRIV int gmc_mh_1x_2x_receive_data(int fd, int revents, void *cb_data);