/** Do a blocking acquisition search in two stages : coarse and fine.
* Do a coarse acqusition to find the approximate code phase and carrier
* frequency, and then a more fine grained acquisition to find the code phase
* and carrier frequency more precisely.
*
* \param prn PRN to search (nap_acq_code_wr_blocking must be called prior)
* \param cp Code phase of the acquisition result
* \param cf Carrier frequency of the acquisition result
* \param snr SNR of the acquisition result
*/
u32 acq_full_two_stage(u8 prn, float* cp, float* cf, float* snr)
{
/* Initial coarse acq. */
float coarse_code_phase;
float coarse_carrier_freq;
float coarse_snr;
u32 coarse_count = nap_timing_count() + 1000;
acq_schedule_load(coarse_count);
while(!acq_get_load_done());
acq_start(prn, 0, 1023, -7000, 7000, 300);
while(!acq_get_done());
acq_get_results(&coarse_code_phase, &coarse_carrier_freq, &coarse_snr);
/* Fine acq. */
u32 fine_count = nap_timing_count() + 2000;
acq_schedule_load(fine_count);
while(!acq_get_load_done());
float fine_cp = propagate_code_phase(coarse_code_phase, coarse_carrier_freq, fine_count - coarse_count);
acq_start(prn, fine_cp-20, fine_cp+20, coarse_carrier_freq-300, coarse_carrier_freq+300, 100);
while(!acq_get_done());
acq_get_results(cp, cf, snr);
return fine_count;
}
/** Do a blocking acquisition search.
* Perform an acquisition for one PRN over a defined code and doppler range.
* Returns the code phase and carrier frequency of the largest peak in the
* search space together with the "SNR" value for that peak defined as
* (peak_magnitude - mean) / std_deviation.
*
* \param prn PRN number - 1 (0..31) to attempt to acquire
* (nap_acq_code_wr_blocking must be called prior).
* \param cp_min Lower bound for code phase search range in chips.
* \param cp_max Upper bound for code phase search range in chips.
* \param cf_min Lower bound for carrier freq. search range in Hz.
* \param cf_max Upper bound for carrier freq. search range in Hz.
* \param cp Pointer to a float where the peak's code phase value will be
* stored in chips.
* \param cf Pointer to a float where the peak's carrier frequency will be
* stored in Hz.
* \param snr Pointer to a float where the "SNR" of the peak will be stored.
*/
void do_acq(u8 prn, float cp_min, float cp_max, float cf_min, float cf_max, float cf_bin_width, float* cp, float* cf, float* snr)
{
acq_start(prn, cp_min, cp_max, cf_min, cf_max, cf_bin_width);
while(acq_state.state == ACQ_RUNNING) {
wait_for_nap_exti();
acq_service_irq();
}
wait_for_nap_exti();
acq_service_irq();
acq_get_results(cp, cf, snr);
}
int main(int argc, char *argv[])
{
char str[256] = {'\0'};
const char* devstring = NULL;
struct acq* acq;
int opt;
// Parse command line options
while ((opt = getopt(argc, argv, "d:h")) != -1) {
switch (opt) {
case 'd':
devstring = optarg;
break;
default: /* '?' */
fprintf(stderr, "Usage: %s [-d devstr]\n", argv[0]);
return (opt == 'h') ? EXIT_SUCCESS : EXIT_FAILURE;
}
}
// Open the connection to the data acquisition device
if (!(acq = acq_init(devstring, data_cb, NULL)))
return EXIT_FAILURE;
fs = acq_get_info(acq, ACQ_FS);
for (;;) {
nstot = 0;
printf("Enter a filename for recording "
"(Ctrl+D to exit):\n");
if (scanf(" %255s%*1c", str) == EOF)
break;
// Create and initialize file for recording
if (acq_prepare_rec(acq, str))
continue;
printf("Press ENTER to start recording\n");
while(getchar() != '\n');
acq_start(acq);
printf("Press ENTER to stop recording\n");
while(getchar() != '\n');
// Stop file recording and close it
acq_stop(acq);
}
// Close the connection to the data acquisition device
acq_close(acq);
return EXIT_SUCCESS;
}
