SDR: Add DC offset removal (DC bias)

pull/1/head
Andreas Eversberg 5 years ago
parent 9e75e64787
commit 417151e9a3

@ -626,6 +626,11 @@ next_char:
/* dump info */
dump_info();
goto next_char;
#ifdef HAVE_SDR
case 'B':
calibrate_bias();
goto next_char;
#endif
}
/* process call control */

@ -42,4 +42,5 @@ void sighandler(int sigset);
void main_mobile(int *quit, int latency, int interval, void (*myhandler)(void), const char *station_id, int station_id_digits);
void dump_info(void);
void calibrate_bias(void);

@ -391,6 +391,39 @@ error:
return NULL;
}
double bias_I, bias_Q; /* calculated bias */
int bias_count = -1; /* number of calculations */
void calibrate_bias(void)
{
bias_count = 0;
bias_I = 0.0;
bias_Q = 0.0;
}
static void sdr_bias(float *buffer, int count)
{
int i;
if (bias_count < sdr_config->samplerate) {
for (i = 0; i < count; i++) {
bias_I += *buffer++;
bias_Q += *buffer++;
}
bias_count += count;
if (bias_count >= sdr_config->samplerate) {
bias_I /= bias_count;
bias_Q /= bias_count;
PDEBUG(DSDR, DEBUG_INFO, "DC bias calibration finished.\n");
}
} else {
for (i = 0; i < count; i++) {
*buffer++ -= bias_I;
*buffer++ -= bias_Q;
}
}
}
static void *sdr_write_child(void *arg)
{
sdr_t *sdr = (sdr_t *)arg;
@ -461,6 +494,8 @@ static void *sdr_read_child(void *arg)
if (sdr_config->soapy)
count = soapy_receive(sdr->thread_read.buffer2, num);
#endif
if (bias_count >= 0)
sdr_bias(sdr->thread_read.buffer2, count);
if (count > 0) {
#ifdef DEBUG_BUFFER
printf("Thread read %d samples from SDR and writes them to read buffer.\n", count);
@ -767,6 +802,8 @@ int sdr_read(void *inst, sample_t **samples, int num, int channels, double *rf_l
if (sdr_config->soapy)
count = soapy_receive(buff, num);
#endif
if (bias_count >= 0)
sdr_bias(buff, count);
if (count <= 0)
return count;
}

@ -95,6 +95,7 @@ void sdr_config_print_hotkeys(void)
{
printf("Press 'q' key to toggle display of RX I/Q vector.\n");
printf("Press 's' key to toggle display of RX spectrum.\n");
printf("Press shift + 'B' key to remove DC level.\n");
}
#define OPT_SDR_UHD 1500

@ -43,7 +43,8 @@
* loss_time, the 'loss' condition is returned.
*/
#define SQUELCH_INIT_TIME 1.0 /* wait some time before performing squelch */
/* NOTE: SQUELCH must be calibrated !AFTER! DC bias, to get the actual noise floor */
#define SQUELCH_INIT_TIME 1.1 /* wait some time before performing squelch */
#define SQUELCH_AUTO_TIME 1.0 /* duration of squelch quelch calibration */
#define SQUELCH_AUTO_OFFSET 6.0 /* auto calibration: offset above noise floor */

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