New functions rtlsdr_set_tuner_bandwidth()

Signed-off-by: Steve Markgraf <steve@steve-m.de>

include/rtl-sdr.h

@@ -215,6 +215,15 @@ RTLSDR_API int rtlsdr_get_tuner_gains(rtlsdr_dev_t *dev, int *gains);
  */
 RTLSDR_API int rtlsdr_set_tuner_gain(rtlsdr_dev_t *dev, int gain);
 
+/*!
+ * Set the bandwidth for the device.
+ *
+ * \param dev the device handle given by rtlsdr_open()
+ * \param bw bandwidth in Hz. Zero means automatic BW selection.
+ * \return 0 on success
+ */
+RTLSDR_API int rtlsdr_set_tuner_bandwidth(rtlsdr_dev_t *dev, uint32_t bw);
+
 /*!
  * Get actual gain the device is configured to.
  *

src/librtlsdr.c

@@ -113,6 +113,7 @@ struct rtlsdr_dev {
 	rtlsdr_tuner_iface_t *tuner;
 	uint32_t tun_xtal; /* Hz */
 	uint32_t freq; /* Hz */
+	uint32_t bw;
 	uint32_t offs_freq; /* Hz */
 	int corr; /* ppm */
 	int gain; /* tenth dB */
@@ -1008,6 +1009,24 @@ int rtlsdr_get_tuner_gains(rtlsdr_dev_t *dev, int *gains)
 	}
 }
 
+int rtlsdr_set_tuner_bandwidth(rtlsdr_dev_t *dev, uint32_t bw)
+{
+	int r = 0;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->tuner->set_bw) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_bw(dev, bw > 0 ? bw : dev->rate);
+		rtlsdr_set_i2c_repeater(dev, 0);
+		if (r)
+			return r;
+		dev->bw = bw;
+	}
+	return r;
+}
+
 int rtlsdr_set_tuner_gain(rtlsdr_dev_t *dev, int gain)
 {
 	int r = 0;
@@ -1095,14 +1114,14 @@ int rtlsdr_set_sample_rate(rtlsdr_dev_t *dev, uint32_t samp_rate)
 	if ( ((double)samp_rate) != real_rate )
 		fprintf(stderr, "Exact sample rate is: %f Hz\n", real_rate);
 
+	dev->rate = (uint32_t)real_rate;
+
 	if (dev->tuner && dev->tuner->set_bw) {
 		rtlsdr_set_i2c_repeater(dev, 1);
-		dev->tuner->set_bw(dev, (int)real_rate);
+		dev->tuner->set_bw(dev, dev->bw > 0 ? dev->bw : dev->rate);
 		rtlsdr_set_i2c_repeater(dev, 0);
 	}
 
-	dev->rate = (uint32_t)real_rate;
-
 	tmp = (rsamp_ratio >> 16);
 	r |= rtlsdr_demod_write_reg(dev, 1, 0x9f, tmp, 2);
 	tmp = rsamp_ratio & 0xffff;
@@ -1219,6 +1238,7 @@ int rtlsdr_get_direct_sampling(rtlsdr_dev_t *dev)
 int rtlsdr_set_offset_tuning(rtlsdr_dev_t *dev, int on)
 {
 	int r = 0;
+	int bw;
 
 	if (!dev)
 		return -1;
@@ -1236,7 +1256,14 @@ int rtlsdr_set_offset_tuning(rtlsdr_dev_t *dev, int on)
 
 	if (dev->tuner && dev->tuner->set_bw) {
 		rtlsdr_set_i2c_repeater(dev, 1);
-		dev->tuner->set_bw(dev, on ? (2 * dev->offs_freq) : dev->rate);
+		if (on) {
+			bw = 2 * dev->offs_freq;
+		} else if (dev->bw > 0) {
+			bw = dev->bw;
+		} else {
+			bw = dev->rate;
+		}
+		dev->tuner->set_bw(dev, bw);
 		rtlsdr_set_i2c_repeater(dev, 0);
 	}