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Add --direct option for rtlsdr direct sampling

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This commit is contained in:
Oliver Jowett 2018-07-23 20:37:01 +01:00
parent 1caabc5ad8
commit 2b00c05465
1 changed files with 38 additions and 28 deletions
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66
sdr_rtlsdr.c
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@ -57,6 +57,7 @@ static struct {
rtlsdr_dev_t *dev; rtlsdr_dev_t *dev;
bool digital_agc; bool digital_agc;
int ppm_error; int ppm_error;
int direct_sampling;
iq_convert_fn converter; iq_convert_fn converter;
struct converter_state *converter_state; struct converter_state *converter_state;
@ -71,6 +72,7 @@ void rtlsdrInitConfig()
RTLSDR.dev = NULL; RTLSDR.dev = NULL;
RTLSDR.digital_agc = false; RTLSDR.digital_agc = false;
RTLSDR.ppm_error = 0; RTLSDR.ppm_error = 0;
RTLSDR.direct_sampling = 0;
RTLSDR.converter = NULL; RTLSDR.converter = NULL;
RTLSDR.converter_state = NULL; RTLSDR.converter_state = NULL;
} }
@ -142,6 +144,7 @@ void rtlsdrShowHelp()
printf("--device <index|serial> select device by index or serial number\n"); printf("--device <index|serial> select device by index or serial number\n");
printf("--enable-agc enable digital AGC (not tuner AGC!)\n"); printf("--enable-agc enable digital AGC (not tuner AGC!)\n");
printf("--ppm <correction> set oscillator frequency correction in PPM\n"); printf("--ppm <correction> set oscillator frequency correction in PPM\n");
printf("--direct <0|1|2> set direct sampling mode\n");
printf("\n"); printf("\n");
} }
@ -154,6 +157,8 @@ bool rtlsdrHandleOption(int argc, char **argv, int *jptr)
RTLSDR.digital_agc = true; RTLSDR.digital_agc = true;
} else if (!strcmp(argv[j], "--ppm") && more) { } else if (!strcmp(argv[j], "--ppm") && more) {
RTLSDR.ppm_error = atoi(argv[++j]); RTLSDR.ppm_error = atoi(argv[++j]);
} else if (!strcmp(argv[j], "--direct") && more) {
RTLSDR.direct_sampling = atoi(argv[++j]);
} else { } else {
return false; return false;
} }
@ -196,39 +201,44 @@ bool rtlsdrOpen(void) {
} }
// Set gain, frequency, sample rate, and reset the device // Set gain, frequency, sample rate, and reset the device
if (Modes.gain == MODES_AUTO_GAIN) { if (RTLSDR.direct_sampling) {
fprintf(stderr, "rtlsdr: enabling tuner AGC\n"); fprintf(stderr, "rtlsdr: direct sampling from input %d\n", RTLSDR.direct_sampling);
rtlsdr_set_tuner_gain_mode(RTLSDR.dev, 0); rtlsdr_set_direct_sampling(RTLSDR.dev, RTLSDR.direct_sampling);
} else { } else {
int *gains; if (Modes.gain == MODES_AUTO_GAIN) {
int numgains; fprintf(stderr, "rtlsdr: enabling tuner AGC\n");
rtlsdr_set_tuner_gain_mode(RTLSDR.dev, 0);
} else {
int *gains;
int numgains;
numgains = rtlsdr_get_tuner_gains(RTLSDR.dev, NULL); numgains = rtlsdr_get_tuner_gains(RTLSDR.dev, NULL);
if (numgains <= 0) { if (numgains <= 0) {
fprintf(stderr, "rtlsdr: error getting tuner gains\n"); fprintf(stderr, "rtlsdr: error getting tuner gains\n");
return false; return false;
} }
gains = malloc(numgains * sizeof(int)); gains = malloc(numgains * sizeof(int));
if (rtlsdr_get_tuner_gains(RTLSDR.dev, gains) != numgains) { if (rtlsdr_get_tuner_gains(RTLSDR.dev, gains) != numgains) {
fprintf(stderr, "rtlsdr: error getting tuner gains\n"); fprintf(stderr, "rtlsdr: error getting tuner gains\n");
free(gains);
return false;
}
int target = (Modes.gain == MODES_MAX_GAIN ? 9999 : Modes.gain);
int closest = -1;
for (int i = 0; i < numgains; ++i) {
if (closest == -1 || abs(gains[i] - target) < abs(gains[closest] - target))
closest = i;
}
rtlsdr_set_tuner_gain(RTLSDR.dev, gains[closest]);
free(gains); free(gains);
return false;
fprintf(stderr, "rtlsdr: tuner gain set to %.1f dB\n",
rtlsdr_get_tuner_gain(RTLSDR.dev)/10.0);
} }
int target = (Modes.gain == MODES_MAX_GAIN ? 9999 : Modes.gain);
int closest = -1;
for (int i = 0; i < numgains; ++i) {
if (closest == -1 || abs(gains[i] - target) < abs(gains[closest] - target))
closest = i;
}
rtlsdr_set_tuner_gain(RTLSDR.dev, gains[closest]);
free(gains);
fprintf(stderr, "rtlsdr: tuner gain set to %.1f dB\n",
rtlsdr_get_tuner_gain(RTLSDR.dev)/10.0);
} }
if (RTLSDR.digital_agc) { if (RTLSDR.digital_agc) {