forked from cellular-infrastructure/osmocom-analog
Add filter switch to FSK modulator
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parent
6dcc8baad4
commit
445af0c0a2
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@ -340,7 +340,7 @@ int main(int argc, char *argv[])
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sprintf(funkwahl, "wwww%c%s%se%c%s%se", start_digit, station_id, dialing + 1, start_digit, station_id, dialing + 1);
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/* init fsk */
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if (fsk_mod_init(&fsk_mod, NULL, fsk_send_bit, samplerate, BIT_RATE, F0, F1, 1.0, 0) < 0) {
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if (fsk_mod_init(&fsk_mod, NULL, fsk_send_bit, samplerate, BIT_RATE, F0, F1, 1.0, 0, 0) < 0) {
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PDEBUG(DDSP, DEBUG_ERROR, "FSK init failed!\n");
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goto exit;
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}
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@ -96,7 +96,7 @@ int dsp_init_sender(bnetz_t *bnetz, double squelch_db)
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PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f (%.3f KHz deviation @ 2000 Hz)\n", TX_PEAK_FSK, 4.0);
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/* init fsk */
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if (fsk_mod_init(&bnetz->fsk_mod, bnetz, fsk_send_bit, bnetz->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 0) < 0) {
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if (fsk_mod_init(&bnetz->fsk_mod, bnetz, fsk_send_bit, bnetz->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 0, 0) < 0) {
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PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n");
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return -EINVAL;
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}
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@ -39,7 +39,7 @@
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* level = level to modulate the frequencies
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* coherent = use coherent modulation (FFSK)
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*/
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int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent)
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int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent, int filter)
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{
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int i;
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int rc;
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@ -76,9 +76,9 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa
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PDEBUG(DDSP, DEBUG_DEBUG, "Bitduration of %.4f bits per sample @ %d.\n", fsk->bits_per_sample, samplerate);
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fsk->phaseshift65536[0] = f0 / (double)samplerate * 65536.0;
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PDEBUG(DDSP, DEBUG_DEBUG, "phaseshift65536[0] = %.4f\n", fsk->phaseshift65536[0]);
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PDEBUG(DDSP, DEBUG_DEBUG, "F0 = %.0f Hz (phaseshift65536[0] = %.4f)\n", f0, fsk->phaseshift65536[0]);
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fsk->phaseshift65536[1] = f1 / (double)samplerate * 65536.0;
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PDEBUG(DDSP, DEBUG_DEBUG, "phaseshift65536[1] = %.4f\n", fsk->phaseshift65536[1]);
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PDEBUG(DDSP, DEBUG_DEBUG, "F1 = %.0f Hz (phaseshift65536[1] = %.4f)\n", f1, fsk->phaseshift65536[1]);
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/* use coherent modulation, i.e. each bit has an integer number of
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* half waves and starts/ends at zero crossing
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@ -86,6 +86,7 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa
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if (coherent) {
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double waves;
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PDEBUG(DDSP, DEBUG_DEBUG, "enable coherent FSK modulation mode\n");
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fsk->coherent = 1;
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waves = (f0 / bitrate);
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if (fabs(round(waves * 2) - (waves * 2)) > 0.001) {
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@ -101,6 +102,20 @@ int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int sa
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fsk->cycles_per_bit65536[1] = waves * 65536.0;
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}
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/* if filter is enabled, add a band pass filter to smoot the spectrum of the tones
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* the bandwidth is twice the difference between f0 and f1
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*/
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if (filter) {
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double low = (f0 + f1) / 2.0 - fabs(f0 - f1);
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double high = (f0 + f1) / 2.0 + fabs(f0 - f1);
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PDEBUG(DDSP, DEBUG_DEBUG, "enable filter to smooth FSK transmission. (frequency rage %.0f .. %.0f)\n", low, high);
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fsk->filter = 1;
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/* use fourth order (2 iter) filter, since it is as fast as second order (1 iter) filter */
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iir_highpass_init(&fsk->lp[0], low, samplerate, 2);
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iir_lowpass_init(&fsk->lp[1], high, samplerate, 2);
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}
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return 0;
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error:
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@ -180,6 +195,12 @@ next_bit:
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goto next_bit;
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}
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/* post filter */
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if (fsk->filter) {
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iir_process(&fsk->lp[0], sample, length);
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iir_process(&fsk->lp[1], sample, length);
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}
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done:
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fsk->tx_phase65536 = phase;
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@ -15,6 +15,8 @@ typedef struct fsk_mod {
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int low_bit, high_bit; /* a low or high deviation means which bit? */
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int tx_bit; /* current transmitting bit (-1 if not set) */
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double tx_bitpos; /* current transmit position in bit */
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int filter; /* set, if filters are used */
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iir_filter_t lp[2]; /* filter to smoot transmission spectrum */
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} fsk_mod_t;
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typedef struct fsk_demod {
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@ -30,7 +32,7 @@ typedef struct fsk_demod {
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double rx_bitadjust; /* how much does a bit change cause the sample clock to be adjusted in phase */
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} fsk_demod_t;
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int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent);
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int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent, int filter);
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void fsk_mod_cleanup(fsk_mod_t *fsk);
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int fsk_mod_send(fsk_mod_t *fsk, sample_t *sample, int length, int add);
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void fsk_mod_tx_reset(fsk_mod_t *fsk);
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@ -120,7 +120,7 @@ int dsp_init_sender(nmt_t *nmt, double deviation_factor)
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PDEBUG(DDSP, DEBUG_DEBUG, "Using Supervisory level of %.3f (%.3f KHz deviation @ 4015 Hz)\n", TX_PEAK_SUPER * deviation_factor, 0.3 * deviation_factor);
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/* init fsk */
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if (fsk_mod_init(&nmt->fsk_mod, nmt, fsk_send_bit, nmt->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 1) < 0) {
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if (fsk_mod_init(&nmt->fsk_mod, nmt, fsk_send_bit, nmt->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 1, 0) < 0) {
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PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n");
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return -EINVAL;
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}
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@ -85,7 +85,7 @@ int dsp_init_sender(r2000_t *r2000)
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PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f\n", TX_PEAK_FSK);
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/* init fsk */
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if (fsk_mod_init(&r2000->fsk_mod, r2000, fsk_send_bit, r2000->sender.samplerate, FSK_BIT_RATE, FSK_F0, FSK_F1, TX_PEAK_FSK, 1) < 0) {
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if (fsk_mod_init(&r2000->fsk_mod, r2000, fsk_send_bit, r2000->sender.samplerate, FSK_BIT_RATE, FSK_F0, FSK_F1, TX_PEAK_FSK, 1, 0) < 0) {
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PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n");
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return -EINVAL;
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}
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@ -99,7 +99,7 @@ int dsp_init_sender(r2000_t *r2000)
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r2000->rx_max = 144;
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/* init supervisorty fsk */
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if (fsk_mod_init(&r2000->super_fsk_mod, r2000, super_send_bit, r2000->sender.samplerate, SUPER_BIT_RATE, SUPER_F0, SUPER_F1, TX_PEAK_SUPER, 0) < 0) {
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if (fsk_mod_init(&r2000->super_fsk_mod, r2000, super_send_bit, r2000->sender.samplerate, SUPER_BIT_RATE, SUPER_F0, SUPER_F1, TX_PEAK_SUPER, 0, 0) < 0) {
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PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n");
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return -EINVAL;
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}
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