hantek-6xxx: add coupling support

Sainsmart DDS-120 supports AC or DC coupling. Add driver support
to control that feature.

src/hardware/hantek-6xxx/api.c

@@ -43,12 +43,17 @@ static const uint32_t devopts[] = {
 
 static const uint32_t devopts_cg[] = {
 	SR_CONF_VDIV | SR_CONF_GET | SR_CONF_SET | SR_CONF_LIST,
+	SR_CONF_COUPLING | SR_CONF_GET | SR_CONF_SET | SR_CONF_LIST,
 };
 
 static const char *channel_names[] = {
 	"CH1", "CH2",
 };
 
+static const char *coupling[] = {
+	"AC", "DC",
+};
+
 static const struct hantek_6xxx_profile dev_profiles[] = {
 	{
 		0x04b4, 0x6022, 0x04b5, 0x6022,
@@ -103,6 +108,7 @@ static struct sr_dev_inst *hantek_6xxx_dev_new(const struct hantek_6xxx_profile
 	for (i = 0; i < NUM_CHANNELS; i++) {
 		devc->ch_enabled[i] = TRUE;
 		devc->voltage[i] = DEFAULT_VOLTAGE;
+		devc->coupling[i] = DEFAULT_COUPLING;
 	}
 
 	devc->sample_buf = NULL;
@@ -382,6 +388,9 @@ static int config_get(uint32_t key, GVariant **data, const struct sr_dev_inst *s
 			vdiv = vdivs[devc->voltage[ch_idx]];
 			*data = g_variant_new("(tt)", vdiv[0], vdiv[1]);
 			break;
+		case SR_CONF_COUPLING:
+			*data = g_variant_new_string(coupling[devc->coupling[ch_idx]]);
+			break;
 		}
 	}
 
@@ -395,6 +404,7 @@ static int config_set(uint32_t key, GVariant *data, const struct sr_dev_inst *sd
 	uint64_t p, q;
 	int tmp_int, ch_idx, ret;
 	unsigned int i;
+	const char *tmp_str;
 
 	if (sdi->status != SR_ST_ACTIVE)
 		return SR_ERR_DEV_CLOSED;
@@ -440,6 +450,17 @@ static int config_set(uint32_t key, GVariant *data, const struct sr_dev_inst *sd
 			} else
 				ret = SR_ERR_ARG;
 			break;
+		case SR_CONF_COUPLING:
+			tmp_str = g_variant_get_string(data, NULL);
+			for (i = 0; coupling[i]; i++) {
+				if (!strcmp(tmp_str, coupling[i])) {
+					devc->coupling[ch_idx] = i;
+					break;
+				}
+			}
+			if (coupling[i] == 0)
+				ret = SR_ERR_ARG;
+			break;
 		default:
 			ret = SR_ERR_NA;
 			break;
@@ -493,6 +514,9 @@ static int config_list(uint32_t key, GVariant **data, const struct sr_dev_inst *
 			*data = g_variant_new_fixed_array(G_VARIANT_TYPE_UINT32,
 				devopts_cg, ARRAY_SIZE(devopts_cg), sizeof(uint32_t));
 			break;
+		case SR_CONF_COUPLING:
+			*data = g_variant_new_strv(coupling, ARRAY_SIZE(coupling));
+			break;
 		case SR_CONF_VDIV:
 			g_variant_builder_init(&gvb, G_VARIANT_TYPE_ARRAY);
 			for (i = 0; i < ARRAY_SIZE(vdivs); i++) {

src/hardware/hantek-6xxx/protocol.c

@@ -215,6 +215,16 @@ SR_PRIV int hantek_6xxx_update_vdiv(const struct sr_dev_inst *sdi)
 	return MIN(ret1, ret2);
 }
 
+SR_PRIV int hantek_6xxx_update_coupling(const struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc = sdi->priv;
+	uint8_t coupling = 0xFF & ((devc->coupling[1] << 4) | devc->coupling[0]);
+
+	sr_dbg("update coupling 0x%x", coupling);
+
+	return write_control(sdi, COUPLING_REG, coupling);
+}
+
 SR_PRIV int hantek_6xxx_update_channels(const struct sr_dev_inst *sdi)
 {
 	struct dev_context *devc = sdi->priv;
@@ -230,6 +240,7 @@ SR_PRIV int hantek_6xxx_init(const struct sr_dev_inst *sdi)
 
 	hantek_6xxx_update_samplerate(sdi);
 	hantek_6xxx_update_vdiv(sdi);
+	hantek_6xxx_update_coupling(sdi);
 	// hantek_6xxx_update_channels(sdi); /* Only 2 channel mode supported. */
 
 	return SR_OK;

src/hardware/hantek-6xxx/protocol.h

@@ -31,6 +31,7 @@
 #define MAX_RENUM_DELAY_MS	3000
 
 #define DEFAULT_VOLTAGE		2
+#define DEFAULT_COUPLING        COUPLING_DC
 #define DEFAULT_SAMPLERATE	SR_MHZ(8)
 
 #define NUM_CHANNELS		2
@@ -71,6 +72,7 @@ enum control_requests {
 	SAMPLERATE_REG = 0xe2,
 	TRIGGER_REG    = 0xe3,
 	CHANNELS_REG   = 0xe4,
+	COUPLING_REG   = 0xe5,
 };
 
 enum states {
@@ -80,6 +82,11 @@ enum states {
 	STOPPING,
 };
 
+enum couplings {
+	COUPLING_AC = 0,
+	COUPLING_DC,
+};
+
 struct hantek_6xxx_profile {
 	/* VID/PID after cold boot */
 	uint16_t orig_vid;
@@ -116,6 +123,7 @@ struct dev_context {
 
 	gboolean ch_enabled[NUM_CHANNELS];
 	int voltage[NUM_CHANNELS];
+	int coupling[NUM_CHANNELS];
 	uint64_t samplerate;
 
 	uint64_t limit_msec;
@@ -130,6 +138,7 @@ SR_PRIV int hantek_6xxx_get_channeldata(const struct sr_dev_inst *sdi,
 SR_PRIV int hantek_6xxx_start_data_collecting(const struct sr_dev_inst *sdi);
 SR_PRIV int hantek_6xxx_stop_data_collecting(const struct sr_dev_inst *sdi);
 
+SR_PRIV int hantek_6xxx_update_coupling(const struct sr_dev_inst *sdi);
 SR_PRIV int hantek_6xxx_update_samplerate(const struct sr_dev_inst *sdi);
 SR_PRIV int hantek_6xxx_update_vdiv(const struct sr_dev_inst *sdi);
 SR_PRIV int hantek_6xxx_update_channels(const struct sr_dev_inst *sdi);