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add function for offset tuning with zero-IF tuners 

Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Steve Markgraf 2012-10-06 19:43:25 +02:00
parent 1e67d2a9a3
commit b70c7d99f1
2 changed files with 47 additions and 2 deletions
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10
include/rtl-sdr.h
View File

@ -241,6 +241,16 @@ RTLSDR_API int rtlsdr_set_agc_mode(rtlsdr_dev_t *dev, int on);
*/
RTLSDR_API int rtlsdr_set_direct_sampling(rtlsdr_dev_t *dev, int on);
/*!
* Enable or disable offset tuning for zero-IF tuners, which allows to avoid
* problems caused by the DC offset of the ADCs and 1/f noise.
*
* \param dev the device handle given by rtlsdr_open()
* \param on 0 means disabled, 1 enabled
* \return 0 on success
*/
RTLSDR_API int rtlsdr_set_offset_tuning(rtlsdr_dev_t *dev, int on);
/* streaming functions */
RTLSDR_API int rtlsdr_reset_buffer(rtlsdr_dev_t *dev);

39
src/librtlsdr.c
View File

@ -85,6 +85,7 @@ struct rtlsdr_dev {
rtlsdr_tuner_iface_t *tuner;
uint32_t tun_xtal; /* Hz */
uint32_t freq; /* Hz */
uint32_t offs_freq; /* Hz */
int corr; /* ppm */
int gain; /* tenth dB */
struct e4k_state e4k_s;
@ -105,9 +106,18 @@ int e4000_set_freq(void *dev, uint32_t freq) {
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
return e4k_tune_freq(&devt->e4k_s, freq);
}
int e4000_set_bw(void *dev, int bw) {
return 0;
int r = 0;
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_MIX, bw);
r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_RC, bw);
r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_CHAN, bw);
return r;
}
int e4000_set_gain(void *dev, int gain) {
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
int mixgain = (gain > 340) ? 12 : 4;
@ -708,7 +718,7 @@ int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq)
r = rtlsdr_set_if_freq(dev, freq);
} else if (dev->tuner && dev->tuner->set_freq) {
rtlsdr_set_i2c_repeater(dev, 1);
r = dev->tuner->set_freq(dev, freq);
r = dev->tuner->set_freq(dev, freq - dev->offs_freq);
rtlsdr_set_i2c_repeater(dev, 0);
}
@ -1009,6 +1019,31 @@ int rtlsdr_set_direct_sampling(rtlsdr_dev_t *dev, int on)
return r;
}
int rtlsdr_set_offset_tuning(rtlsdr_dev_t *dev, int on)
{
int r = 0;
if (!dev)
return -1;
if (dev->tuner_type == RTLSDR_TUNER_R820T)
return -2;
/* based on keenerds 1/f noise measurements */
dev->offs_freq = on ? ((dev->rate / 2) * 170 / 100) : 0;
r |= rtlsdr_set_if_freq(dev, dev->offs_freq);
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);
rtlsdr_set_i2c_repeater(dev, 0);
}
r |= rtlsdr_set_center_freq(dev, dev->freq);
return r;
}
static rtlsdr_dongle_t *find_known_device(uint16_t vid, uint16_t pid)
{
unsigned int i;