diff --git a/hardware/hantek-dso/api.c b/hardware/hantek-dso/api.c
index 6c1042ff..0f193113 100644
--- a/hardware/hantek-dso/api.c
+++ b/hardware/hantek-dso/api.c
@@ -125,6 +125,13 @@ static char *filter_targets[] = {
 	NULL
 };
 
+static char *coupling[] = {
+	"AC",
+	"DC",
+	"GND",
+	NULL
+};
+
 SR_PRIV libusb_context *usb_context = NULL;
 SR_PRIV GSList *dev_insts = NULL;
 
@@ -516,6 +523,19 @@ static int hw_dev_config_set(int dev_index, int hwcap, void *value)
 		if (vdivs[i].p == 0 && vdivs[i].q == 0)
 			ret = SR_ERR_ARG;
 		break;
+	case SR_HWCAP_COUPLING:
+		/* TODO not supporting coupling per channel yet */
+		tmp_str = value;
+		for (i = 0; coupling[i]; i++) {
+			if (!strcmp(tmp_str, coupling[i])) {
+				ctx->coupling_ch1 = i;
+				ctx->coupling_ch2 = i;
+				break;
+			}
+		}
+		if (coupling[i] == 0)
+			ret = SR_ERR_ARG;
+		break;
 	default:
 		ret = SR_ERR_ARG;
 	}
diff --git a/hardware/hantek-dso/dso.c b/hardware/hantek-dso/dso.c
index 00dde6da..6e704cfb 100644
--- a/hardware/hantek-dso/dso.c
+++ b/hardware/hantek-dso/dso.c
@@ -445,17 +445,18 @@ SR_PRIV int dso_set_relays(struct context *ctx)
 	uint8_t relays[] = { 0x00, 0x04, 0x08, 0x02, 0x20, 0x40, 0x10, 0x01,
 			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
 
-	sr_dbg("hantek-dso: sending CTRL_SETRELAYS");
+	sr_dbg("hantek-dso: preparing CTRL_SETRELAYS");
 
 	cv1 = ctx->voltage_ch1 / 3;
 	cv2 = ctx->voltage_ch2 / 3;
-relays[0] = 0x01;
+
 	if (cv1 > 0)
 		relays[1] = ~relays[1];
 
 	if (cv1 > 1)
 		relays[2] = ~relays[2];
 
+	sr_dbg("hantek-dso: CH1 coupling %d", ctx->coupling_ch1);
 	if (ctx->coupling_ch1 != COUPLING_AC)
 		relays[3] = ~relays[3];
 
@@ -465,6 +466,7 @@ relays[0] = 0x01;
 	if (cv2 > 1)
 		relays[5] = ~relays[5];
 
+	sr_dbg("hantek-dso: CH2 coupling %d", ctx->coupling_ch1);
 	if (ctx->coupling_ch2 != COUPLING_AC)
 		relays[6] = ~relays[6];
 
@@ -477,6 +479,7 @@ relays[0] = 0x01;
 		sr_err("failed to set relays: %d", ret);
 		return SR_ERR;
 	}
+	sr_dbg("hantek-dso: sent CTRL_SETRELAYS");
 
 	return SR_OK;
 }
diff --git a/hardware/hantek-dso/dso.h b/hardware/hantek-dso/dso.h
index 53d953e1..145f584b 100644
--- a/hardware/hantek-dso/dso.h
+++ b/hardware/hantek-dso/dso.h
@@ -72,12 +72,14 @@ enum dso_commands {
 	cmdGetLogicalData
 };
 
+/* Must match the coupling table. */
 enum couplings {
 	COUPLING_AC = 0,
 	COUPLING_DC,
-	COUPLING_OFF
+	COUPLING_GND
 };
 
+/* Must match the timebases table. */
 enum time_bases {
 	TIME_10us = 0,
 	TIME_20us,
@@ -96,7 +98,7 @@ enum time_bases {
 	TIME_400ms
 };
 
-/* Must match the vdivs table, these are just handy indexes into it. */
+/* Must match the vdivs table. */
 enum {
 	VDIV_10MV,
 	VDIV_20MV,