SDR: disable TX or RX by setting TX or RX frequency to 0

This way it is possible to use SDR simplex

src/common/sdr.c

@@ -81,7 +81,7 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 {
 	sdr_t *sdr;
 	double bandwidth;
-	double tx_center_frequency, rx_center_frequency;
+	double tx_center_frequency = 0.0, rx_center_frequency = 0.0;
 	int rc;
 	int c;
 
@@ -117,29 +117,24 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 		PDEBUG(DSDR, DEBUG_ERROR, "NO MEM!\n");
 		goto error;
 	}
+
+	if (tx_frequency) {
+		/* calculate required bandwidth (IQ rate) */
 		for (c = 0; c < channels; c++) {
-		PDEBUG(DSDR, DEBUG_INFO, "Frequency #%d: TX = %.6f MHz, RX = %.6f MHz\n", c, tx_frequency[c] / 1e6, rx_frequency[c] / 1e6);
+			PDEBUG(DSDR, DEBUG_INFO, "Frequency #%d: TX = %.6f MHz\n", c, tx_frequency[c] / 1e6);
 			sdr->chan[c].tx_frequency = tx_frequency[c];
-		sdr->chan[c].rx_frequency = rx_frequency[c];
 		}
 		if (sdr->paging_channel) {
 			PDEBUG(DSDR, DEBUG_INFO, "Paging Frequency: TX = %.6f MHz\n", paging_frequency / 1e6);
 			sdr->chan[sdr->paging_channel].tx_frequency = paging_frequency;
 		}
 
-	/* calculate required bandwidth (IQ rate) */
 		double tx_low_frequency = sdr->chan[0].tx_frequency, tx_high_frequency = sdr->chan[0].tx_frequency;
-	double rx_low_frequency = sdr->chan[0].rx_frequency, rx_high_frequency = sdr->chan[0].rx_frequency;
-	double range;
 		for (c = 1; c < channels; c++) {
 			if (sdr->chan[c].tx_frequency < tx_low_frequency)
 				tx_low_frequency = sdr->chan[c].tx_frequency;
 			if (sdr->chan[c].tx_frequency > tx_high_frequency)
 				tx_high_frequency = sdr->chan[c].tx_frequency;
-		if (sdr->chan[c].rx_frequency < rx_low_frequency)
-			rx_low_frequency = sdr->chan[c].rx_frequency;
-		if (sdr->chan[c].rx_frequency > rx_high_frequency)
-			rx_high_frequency = sdr->chan[c].rx_frequency;
 		}
 		if (sdr->paging_channel) {
 			if (sdr->chan[sdr->paging_channel].tx_frequency < tx_low_frequency)
@@ -148,7 +143,7 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 				tx_high_frequency = sdr->chan[sdr->paging_channel].tx_frequency;
 		}
 		/* range of TX */
-	range = tx_high_frequency - tx_low_frequency;
+		double range = tx_high_frequency - tx_low_frequency;
 		if (range)
 			PDEBUG(DSDR, DEBUG_DEBUG, "Range between all TX Frequencies: %.6f MHz\n", range / 1e6);
 		if (range * 2 > sdr->samplerate) {
@@ -159,8 +154,55 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 			goto error;
 		}
 		tx_center_frequency = (tx_high_frequency + tx_low_frequency) / 2.0;
+		PDEBUG(DSDR, DEBUG_INFO, "Using center frequency: TX %.6f MHz\n", tx_center_frequency / 1e6);
+		/* set offsets to center frequency */
+		for (c = 0; c < channels; c++) {
+			double tx_offset;
+			tx_offset = sdr->chan[c].tx_frequency - tx_center_frequency;
+			PDEBUG(DSDR, DEBUG_DEBUG, "Frequency #%d: TX offset: %.6f MHz\n", c, tx_offset / 1e6);
+			fm_mod_init(&sdr->chan[c].mod, sdr->samplerate, tx_offset, sdr->amplitude);
+		}
+		if (sdr->paging_channel) {
+			double tx_offset;
+			tx_offset = sdr->chan[sdr->paging_channel].tx_frequency - tx_center_frequency;
+			PDEBUG(DSDR, DEBUG_DEBUG, "Paging Frequency: TX offset: %.6f MHz\n", tx_offset / 1e6);
+			fm_mod_init(&sdr->chan[sdr->paging_channel].mod, sdr->samplerate, tx_offset, sdr->amplitude);
+		}
+		/* show gain */
+		PDEBUG(DSDR, DEBUG_INFO, "Using gain: TX %.1f dB\n", sdr_tx_gain);
+		/* open wave */
+		if (sdr_write_iq_tx_wave) {
+			rc = wave_create_record(&sdr->wave_tx_rec, sdr_write_iq_tx_wave, sdr->samplerate, 2, 1.0);
+			if (rc < 0) {
+				PDEBUG(DSDR, DEBUG_ERROR, "Failed to create WAVE recoding instance!\n");
+				goto error;
+			}
+		}
+		if (sdr_read_iq_tx_wave) {
+			rc = wave_create_playback(&sdr->wave_tx_play, sdr_read_iq_tx_wave, sdr->samplerate, 2, 1.0);
+			if (rc < 0) {
+				PDEBUG(DSDR, DEBUG_ERROR, "Failed to create WAVE playback instance!\n");
+				goto error;
+			}
+		}
+	}
+
+	if (rx_frequency) {
+		for (c = 0; c < channels; c++) {
+			PDEBUG(DSDR, DEBUG_INFO, "Frequency #%d: RX = %.6f MHz\n", c, rx_frequency[c] / 1e6);
+			sdr->chan[c].rx_frequency = rx_frequency[c];
+		}
+
+		/* calculate required bandwidth (IQ rate) */
+		double rx_low_frequency = sdr->chan[0].rx_frequency, rx_high_frequency = sdr->chan[0].rx_frequency;
+		for (c = 1; c < channels; c++) {
+			if (sdr->chan[c].rx_frequency < rx_low_frequency)
+				rx_low_frequency = sdr->chan[c].rx_frequency;
+			if (sdr->chan[c].rx_frequency > rx_high_frequency)
+				rx_high_frequency = sdr->chan[c].rx_frequency;
+		}
 		/* range of RX */
-	range = rx_high_frequency - rx_low_frequency;
+		double range = rx_high_frequency - rx_low_frequency;
 		if (range)
 			PDEBUG(DSDR, DEBUG_DEBUG, "Range between all RX Frequencies: %.6f MHz\n", range / 1e6);
 		if (range * 2.0 > sdr->samplerate) {
@@ -169,24 +211,17 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 			goto error;
 		}
 		rx_center_frequency = (rx_high_frequency + rx_low_frequency) / 2.0;
-	PDEBUG(DSDR, DEBUG_INFO, "Using center frequency: TX %.6f MHz, RX %.6f\n", tx_center_frequency / 1e6, rx_center_frequency / 1e6);
+		PDEBUG(DSDR, DEBUG_INFO, "Using center frequency: RX %.6f MHz\n", rx_center_frequency / 1e6);
 		/* set offsets to center frequency */
 		for (c = 0; c < channels; c++) {
-		double tx_offset, rx_offset;
+			double rx_offset;
-		tx_offset = sdr->chan[c].tx_frequency - tx_center_frequency;
 			rx_offset = sdr->chan[c].rx_frequency - rx_center_frequency;
-		PDEBUG(DSDR, DEBUG_DEBUG, "Frequency #%d: TX offset: %.6f MHz, RX offset: %.6f MHz\n", c, tx_offset / 1e6, rx_offset / 1e6);
+			PDEBUG(DSDR, DEBUG_DEBUG, "Frequency #%d: RX offset: %.6f MHz\n", c, rx_offset / 1e6);
-		fm_mod_init(&sdr->chan[c].mod, sdr->samplerate, tx_offset, sdr->amplitude);
 			fm_demod_init(&sdr->chan[c].demod, sdr->samplerate, rx_offset, bandwidth);
 		}
-	if (sdr->paging_channel) {
+		/* show gain */
-		double tx_offset;
+		PDEBUG(DSDR, DEBUG_INFO, "Using gain: RX %.1f dB\n", sdr_rx_gain);
-		tx_offset = sdr->chan[sdr->paging_channel].tx_frequency - tx_center_frequency;
+		/* open wave */
-		PDEBUG(DSDR, DEBUG_DEBUG, "Paging Frequency: TX offset: %.6f MHz\n", tx_offset / 1e6);
-		fm_mod_init(&sdr->chan[sdr->paging_channel].mod, sdr->samplerate, tx_offset, sdr->amplitude);
-	}
-	PDEBUG(DSDR, DEBUG_INFO, "Using gain: TX %.1f dB, RX %.1f dB\n", sdr_tx_gain, sdr_rx_gain);
-
 		if (sdr_write_iq_rx_wave) {
 			rc = wave_create_record(&sdr->wave_rx_rec, sdr_write_iq_rx_wave, sdr->samplerate, 2, 1.0);
 			if (rc < 0) {
@@ -194,13 +229,6 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 				goto error;
 			}
 		}
-	if (sdr_write_iq_tx_wave) {
-		rc = wave_create_record(&sdr->wave_tx_rec, sdr_write_iq_tx_wave, sdr->samplerate, 2, 1.0);
-		if (rc < 0) {
-			PDEBUG(DSDR, DEBUG_ERROR, "Failed to create WAVE recoding instance!\n");
-			goto error;
-		}
-	}
 		if (sdr_read_iq_rx_wave) {
 			rc = wave_create_playback(&sdr->wave_rx_play, sdr_read_iq_rx_wave, sdr->samplerate, 2, 1.0);
 			if (rc < 0) {
@@ -208,12 +236,6 @@ void *sdr_open(const char __attribute__((__unused__)) *audiodev, double *tx_freq
 				goto error;
 			}
 		}
-	if (sdr_read_iq_tx_wave) {
-		rc = wave_create_playback(&sdr->wave_tx_play, sdr_read_iq_tx_wave, sdr->samplerate, 2, 1.0);
-		if (rc < 0) {
-			PDEBUG(DSDR, DEBUG_ERROR, "Failed to create WAVE playback instance!\n");
-			goto error;
-		}
 	}
 
 #ifdef HAVE_UHD

src/common/soapy.c

@@ -68,17 +68,13 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 		return -EIO;
 	}
 
+	if (tx_frequency) {
 		/* set rate */
 		if (SoapySDRDevice_setSampleRate(sdr, SOAPY_SDR_TX, channel, rate) != 0) {
 			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set TX rate to %.0f Hz\n", rate);
 			soapy_close();
 			return -EIO;
 		}
-	if (SoapySDRDevice_setSampleRate(sdr, SOAPY_SDR_RX, channel, rate) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX rate to %.0f Hz\n", rate);
-		soapy_close();
-		return -EIO;
-	}
 
 		/* see what rate actually is */
 		got_rate = SoapySDRDevice_getSampleRate(sdr, SOAPY_SDR_TX, channel);
@@ -87,12 +83,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EINVAL;
 		}
-	got_rate = SoapySDRDevice_getSampleRate(sdr, SOAPY_SDR_RX, channel);
-	if (got_rate != rate) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX rate %.0f Hz is not supported, try %0.f Hz\n", rate, got_rate);
-		soapy_close();
-		return -EINVAL;
-	}
 
 		/* set gain */
 		if (SoapySDRDevice_setGain(sdr, SOAPY_SDR_TX, channel, tx_gain) != 0) {
@@ -100,11 +90,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EIO;
 		}
-	if (SoapySDRDevice_setGain(sdr, SOAPY_SDR_RX, channel, rx_gain) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX gain to %.0f\n", rx_gain);
-		soapy_close();
-		return -EIO;
-	}
 
 		/* see what gain actually is */
 		got_gain = SoapySDRDevice_getGain(sdr, SOAPY_SDR_TX, channel);
@@ -112,11 +97,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			PDEBUG(DUHD, DEBUG_NOTICE, "Given TX gain %.0f is not supported, we use %0.f\n", tx_gain, got_gain);
 			tx_gain = got_gain;
 		}
-	got_gain = SoapySDRDevice_getGain(sdr, SOAPY_SDR_RX, channel);
-	if (got_gain != rx_gain) {
-		PDEBUG(DUHD, DEBUG_NOTICE, "Given RX gain %.3f is not supported, we use %.3f\n", rx_gain, got_gain);
-		rx_gain = got_gain;
-	}
 
 		/* set frequency */
 		if (SoapySDRDevice_setFrequency(sdr, SOAPY_SDR_TX, channel, tx_frequency, NULL) != 0) {
@@ -124,11 +104,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EIO;
 		}
-	if (SoapySDRDevice_setFrequency(sdr, SOAPY_SDR_RX, channel, rx_frequency, NULL) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX frequency to %.0f Hz\n", rx_frequency);
-		soapy_close();
-		return -EIO;
-	}
 
 		/* see what frequency actually is */
 		got_frequency = SoapySDRDevice_getFrequency(sdr, SOAPY_SDR_TX, channel);
@@ -137,12 +112,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EINVAL;
 		}
-	got_frequency = SoapySDRDevice_getFrequency(sdr, SOAPY_SDR_RX, channel);
-	if (got_frequency != rx_frequency) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX frequency %.0f Hz is not supported, try %0.f Hz\n", rx_frequency, got_frequency);
-		soapy_close();
-		return -EINVAL;
-	}
 
 		/* set bandwidth */
 		if (SoapySDRDevice_setBandwidth(sdr, SOAPY_SDR_TX, channel, bandwidth) != 0) {
@@ -150,11 +119,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EIO;
 		}
-	if (SoapySDRDevice_setBandwidth(sdr, SOAPY_SDR_RX, channel, bandwidth) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX bandwidth to %.0f Hz\n", bandwidth);
-		soapy_close();
-		return -EIO;
-	}
 
 		/* see what bandwidth actually is */
 		got_bandwidth = SoapySDRDevice_getBandwidth(sdr, SOAPY_SDR_TX, channel);
@@ -163,12 +127,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EINVAL;
 		}
-	got_bandwidth = SoapySDRDevice_getBandwidth(sdr, SOAPY_SDR_RX, channel);
-	if (got_bandwidth != bandwidth) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX bandwidth %.0f Hz is not supported, try %0.f Hz\n", bandwidth, got_bandwidth);
-		soapy_close();
-		return -EINVAL;
-	}
 
 		/* set up streamer */
 		if (SoapySDRDevice_setupStream(sdr, &txStream, SOAPY_SDR_TX, SOAPY_SDR_CF32, &channel, 1, NULL) != 0) {
@@ -176,11 +134,6 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EIO;
 		}
-	if (SoapySDRDevice_setupStream(sdr, &rxStream, SOAPY_SDR_RX, SOAPY_SDR_CF32, &channel, 1, NULL) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX streamer args\n");
-		soapy_close();
-		return -EIO;
-	}
 
 		/* get buffer sizes */
 		tx_samps_per_buff = SoapySDRDevice_getStreamMTU(sdr, txStream);
@@ -189,12 +142,83 @@ int soapy_open(const char *device_args, double tx_frequency, double rx_frequency
 			soapy_close();
 			return -EIO;
 		}
+	}
+
+	if (rx_frequency) {
+		/* set rate */
+		if (SoapySDRDevice_setSampleRate(sdr, SOAPY_SDR_RX, channel, rate) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX rate to %.0f Hz\n", rate);
+			soapy_close();
+			return -EIO;
+		}
+
+		/* see what rate actually is */
+		got_rate = SoapySDRDevice_getSampleRate(sdr, SOAPY_SDR_RX, channel);
+		if (got_rate != rate) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX rate %.0f Hz is not supported, try %0.f Hz\n", rate, got_rate);
+			soapy_close();
+			return -EINVAL;
+		}
+
+		/* set gain */
+		if (SoapySDRDevice_setGain(sdr, SOAPY_SDR_RX, channel, rx_gain) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX gain to %.0f\n", rx_gain);
+			soapy_close();
+			return -EIO;
+		}
+
+		/* see what gain actually is */
+		got_gain = SoapySDRDevice_getGain(sdr, SOAPY_SDR_RX, channel);
+		if (got_gain != rx_gain) {
+			PDEBUG(DUHD, DEBUG_NOTICE, "Given RX gain %.3f is not supported, we use %.3f\n", rx_gain, got_gain);
+			rx_gain = got_gain;
+		}
+
+		/* set frequency */
+		if (SoapySDRDevice_setFrequency(sdr, SOAPY_SDR_RX, channel, rx_frequency, NULL) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX frequency to %.0f Hz\n", rx_frequency);
+			soapy_close();
+			return -EIO;
+		}
+
+		/* see what frequency actually is */
+		got_frequency = SoapySDRDevice_getFrequency(sdr, SOAPY_SDR_RX, channel);
+		if (got_frequency != rx_frequency) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX frequency %.0f Hz is not supported, try %0.f Hz\n", rx_frequency, got_frequency);
+			soapy_close();
+			return -EINVAL;
+		}
+
+		/* set bandwidth */
+		if (SoapySDRDevice_setBandwidth(sdr, SOAPY_SDR_RX, channel, bandwidth) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX bandwidth to %.0f Hz\n", bandwidth);
+			soapy_close();
+			return -EIO;
+		}
+
+		/* see what bandwidth actually is */
+		got_bandwidth = SoapySDRDevice_getBandwidth(sdr, SOAPY_SDR_RX, channel);
+		if (got_bandwidth != bandwidth) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX bandwidth %.0f Hz is not supported, try %0.f Hz\n", bandwidth, got_bandwidth);
+			soapy_close();
+			return -EINVAL;
+		}
+
+		/* set up streamer */
+		if (SoapySDRDevice_setupStream(sdr, &rxStream, SOAPY_SDR_RX, SOAPY_SDR_CF32, &channel, 1, NULL) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX streamer args\n");
+			soapy_close();
+			return -EIO;
+		}
+
+		/* get buffer sizes */
 		rx_samps_per_buff = SoapySDRDevice_getStreamMTU(sdr, rxStream);
 		if (rx_samps_per_buff == 0) {
 			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX streamer sample buffer\n");
 			soapy_close();
 			return -EIO;
 		}
+	}
 
 	return 0;
 }

src/common/uhd.c

@@ -63,6 +63,7 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 		return -EIO;
 	}
 
+	if (tx_frequency) {
 		/* create streamers */
 		error = uhd_tx_streamer_make(&tx_streamer);
 		if (error) {
@@ -70,20 +71,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-	error = uhd_rx_streamer_make(&rx_streamer);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to create RX streamer\n");
-		uhd_close();
-		return -EIO;
-	}
-
-	/* create rx metadata */
-	error = uhd_rx_metadata_make(&rx_metadata);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to create RX metadata\n");
-		uhd_close();
-		return -EIO;
-	}
 
 		/* set rate */
 		error = uhd_usrp_set_tx_rate(usrp, rate, channel);
@@ -92,12 +79,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-	error = uhd_usrp_set_rx_rate(usrp, rate, channel);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX rate to %.0f Hz\n", rate);
-		uhd_close();
-		return -EIO;
-	}
 
 		/* see what rate actually is */
 		error = uhd_usrp_get_tx_rate(usrp, channel, &got_rate);
@@ -111,17 +92,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EINVAL;
 		}
-	error = uhd_usrp_get_rx_rate(usrp, channel, &got_rate);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX rate\n");
-		uhd_close();
-		return -EIO;
-	}
-	if (got_rate != rate) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX rate %.0f Hz is not supported, try %0.f Hz\n", rate, got_rate);
-		uhd_close();
-		return -EINVAL;
-	}
 
 		/* set gain */
 		error = uhd_usrp_set_tx_gain(usrp, tx_gain, channel, "");
@@ -130,12 +100,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-	error = uhd_usrp_set_rx_gain(usrp, rx_gain, channel, "");
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX gain to %.0f\n", rx_gain);
-		uhd_close();
-		return -EIO;
-	}
 
 		/* see what gain actually is */
 		error = uhd_usrp_get_tx_gain(usrp, channel, "", &got_gain);
@@ -148,16 +112,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			PDEBUG(DUHD, DEBUG_NOTICE, "Given TX gain %.0f is not supported, we use %0.f\n", tx_gain, got_gain);
 			tx_gain = got_gain;
 		}
-	error = uhd_usrp_get_rx_gain(usrp, channel, "", &got_gain);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX gain\n");
-		uhd_close();
-		return -EIO;
-	}
-	if (got_gain != rx_gain) {
-		PDEBUG(DUHD, DEBUG_NOTICE, "Given RX gain %.3f is not supported, we use %.3f\n", rx_gain, got_gain);
-		rx_gain = got_gain;
-	}
 
 		/* set frequency */
 		memset(&tune_request, 0, sizeof(tune_request));
@@ -170,13 +124,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-        tune_request.target_freq = rx_frequency;
-	error = uhd_usrp_set_rx_freq(usrp, &tune_request, channel, &tune_result);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX frequeny to %.0f Hz\n", rx_frequency);
-		uhd_close();
-		return -EIO;
-	}
 
 		/* see what frequency actually is */
 		error = uhd_usrp_get_tx_freq(usrp, channel, &got_frequency);
@@ -190,17 +137,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EINVAL;
 		}
-	error = uhd_usrp_get_rx_freq(usrp, channel, &got_frequency);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX frequency\n");
-		uhd_close();
-		return -EIO;
-	}
-	if (got_frequency != rx_frequency) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX frequency %.0f Hz is not supported, try %0.f Hz\n", rx_frequency, got_frequency);
-		uhd_close();
-		return -EINVAL;
-	}
 
 		/* set bandwidth */
 		if (uhd_usrp_set_tx_bandwidth(usrp, bandwidth, channel) != 0) {
@@ -208,11 +144,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-	if (uhd_usrp_set_rx_bandwidth(usrp, bandwidth, channel) != 0) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX bandwidth to %.0f Hz\n", bandwidth);
-		uhd_close();
-		return -EIO;
-	}
 
 		/* see what bandwidth actually is */
 		error = uhd_usrp_get_tx_bandwidth(usrp, channel, &got_bandwidth);
@@ -226,17 +157,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EINVAL;
 		}
-	error = uhd_usrp_get_rx_bandwidth(usrp, channel, &got_bandwidth);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to get TX bandwidth\n");
-		uhd_close();
-		return -EIO;
-	}
-	if (got_bandwidth != bandwidth) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Given RX bandwidth %.0f Hz is not supported, try %0.f Hz\n", bandwidth, got_bandwidth);
-		uhd_close();
-		return -EINVAL;
-	}
 
 		/* set up streamer */
 		memset(&stream_args, 0, sizeof(stream_args));
@@ -251,12 +171,6 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
-	error = uhd_usrp_get_rx_stream(usrp, &stream_args, rx_streamer);
-	if (error) {
-		PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX streamer args\n");
-		uhd_close();
-		return -EIO;
-	}
 
 		/* get buffer sizes */
 		error = uhd_tx_streamer_max_num_samps(tx_streamer, &tx_samps_per_buff);
@@ -265,12 +179,133 @@ int uhd_open(const char *device_args, double tx_frequency, double rx_frequency,
 			uhd_close();
 			return -EIO;
 		}
+	}
+
+	if (rx_frequency) {
+		/* create streamers */
+		error = uhd_rx_streamer_make(&rx_streamer);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to create RX streamer\n");
+			uhd_close();
+			return -EIO;
+		}
+
+		/* create metadata */
+		error = uhd_rx_metadata_make(&rx_metadata);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to create RX metadata\n");
+			uhd_close();
+			return -EIO;
+		}
+
+		/* set rate */
+		error = uhd_usrp_set_rx_rate(usrp, rate, channel);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX rate to %.0f Hz\n", rate);
+			uhd_close();
+			return -EIO;
+		}
+
+		/* see what rate actually is */
+		error = uhd_usrp_get_rx_rate(usrp, channel, &got_rate);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX rate\n");
+			uhd_close();
+			return -EIO;
+		}
+		if (got_rate != rate) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX rate %.0f Hz is not supported, try %0.f Hz\n", rate, got_rate);
+			uhd_close();
+			return -EINVAL;
+		}
+
+		/* set gain */
+		error = uhd_usrp_set_rx_gain(usrp, rx_gain, channel, "");
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX gain to %.0f\n", rx_gain);
+			uhd_close();
+			return -EIO;
+		}
+
+		/* see what gain actually is */
+		error = uhd_usrp_get_rx_gain(usrp, channel, "", &got_gain);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX gain\n");
+			uhd_close();
+			return -EIO;
+		}
+		if (got_gain != rx_gain) {
+			PDEBUG(DUHD, DEBUG_NOTICE, "Given RX gain %.3f is not supported, we use %.3f\n", rx_gain, got_gain);
+			rx_gain = got_gain;
+		}
+
+		/* set frequency */
+		memset(&tune_request, 0, sizeof(tune_request));
+		tune_request.target_freq = rx_frequency;
+		tune_request.rf_freq_policy = UHD_TUNE_REQUEST_POLICY_AUTO;
+		tune_request.dsp_freq_policy = UHD_TUNE_REQUEST_POLICY_AUTO;
+		error = uhd_usrp_set_rx_freq(usrp, &tune_request, channel, &tune_result);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX frequeny to %.0f Hz\n", rx_frequency);
+			uhd_close();
+			return -EIO;
+		}
+
+		/* see what frequency actually is */
+		error = uhd_usrp_get_rx_freq(usrp, channel, &got_frequency);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX frequency\n");
+			uhd_close();
+			return -EIO;
+		}
+		if (got_frequency != rx_frequency) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX frequency %.0f Hz is not supported, try %0.f Hz\n", rx_frequency, got_frequency);
+			uhd_close();
+			return -EINVAL;
+		}
+
+		/* set bandwidth */
+		if (uhd_usrp_set_rx_bandwidth(usrp, bandwidth, channel) != 0) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX bandwidth to %.0f Hz\n", bandwidth);
+			uhd_close();
+			return -EIO;
+		}
+
+		/* see what bandwidth actually is */
+		error = uhd_usrp_get_rx_bandwidth(usrp, channel, &got_bandwidth);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX bandwidth\n");
+			uhd_close();
+			return -EIO;
+		}
+		if (got_bandwidth != bandwidth) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Given RX bandwidth %.0f Hz is not supported, try %0.f Hz\n", bandwidth, got_bandwidth);
+			uhd_close();
+			return -EINVAL;
+		}
+
+		/* set up streamer */
+		memset(&stream_args, 0, sizeof(stream_args));
+		stream_args.cpu_format = "fc32";
+		stream_args.otw_format = "sc16";
+		stream_args.args = "";
+		stream_args.channel_list = &channel;
+		stream_args.n_channels = 1;
+		error = uhd_usrp_get_rx_stream(usrp, &stream_args, rx_streamer);
+		if (error) {
+			PDEBUG(DUHD, DEBUG_ERROR, "Failed to set RX streamer args\n");
+			uhd_close();
+			return -EIO;
+		}
+
+		/* get buffer sizes */
 		error = uhd_rx_streamer_max_num_samps(rx_streamer, &rx_samps_per_buff);
 		if (error) {
 			PDEBUG(DUHD, DEBUG_ERROR, "Failed to get RX streamer sample buffer\n");
 			uhd_close();
 			return -EIO;
 		}
+	}
 
 	return 0;
 }