main: restructure state management; evaluate a found preamble
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parent
423f1d6416
commit
465d9a1c26
188
impl/src/main.c
188
impl/src/main.c
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@ -18,6 +18,17 @@ typedef enum {
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RX_STATE_DATA,
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RX_STATE_DATA,
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} rx_state_t;
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} rx_state_t;
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void print_complex_array(const char *varname, float complex const *array, size_t len)
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{
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printf("%s=np.array([%f%+fj", varname, crealf(array[0]), cimagf(array[0]));
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for(size_t k = 1; k < len; k++) {
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printf(", %f%+fj", crealf(array[k]), cimagf(array[k]));
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}
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printf("])\n");
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}
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int main(void)
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int main(void)
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{
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{
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uint8_t msg_org[] = "Hello Liquid! This is the message to transmit. Hopefully it can be decoded correctly...";
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uint8_t msg_org[] = "Hello Liquid! This is the message to transmit. Hopefully it can be decoded correctly...";
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@ -28,7 +39,7 @@ int main(void)
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channel_cccf channel = channel_cccf_create();
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channel_cccf channel = channel_cccf_create();
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float snr = 50.0f;
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float snr = 20.0f;
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channel_cccf_add_awgn(channel, -snr, snr);
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channel_cccf_add_awgn(channel, -snr, snr);
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channel_cccf_add_carrier_offset(channel, 0.20f, 1.00f);
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channel_cccf_add_carrier_offset(channel, 0.20f, 1.00f);
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@ -119,81 +130,110 @@ int main(void)
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unsigned int out_len;
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unsigned int out_len;
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symsync_crcf_execute(symsync, &mixed_sample, 1, symsync_out + symsync_out_len, &out_len);
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symsync_crcf_execute(symsync, &mixed_sample, 1, symsync_out + symsync_out_len, &out_len);
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switch(rx_state) {
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case RX_STATE_ACQUISITION:
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if(out_len != 0) {
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// for all the output samples produced, run the frequency
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// estimator. This is an implementation that works with unknown
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// BPSK symbols and therefore can be used during ramp-up and
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// preamble.
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if(out_len < FREQ_EST_L) {
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memmove(phase_history,
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phase_history + out_len,
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(FREQ_EST_L-out_len) * sizeof(phase_history[0]));
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}
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for(unsigned int j = 0; j < out_len; j++) {
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float complex *psymbol = symsync_out + symsync_out_len + j;
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// square the symbol to remove BPSK ambiguity
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float phase = cargf((*psymbol) * (*psymbol));
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phase_history[FREQ_EST_L - out_len + j] = phase;
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}
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// update the frequency estimate
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if(((i/RRC_SPS) % FREQ_EST_L) == 0) {
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float unwrapped_phase_history[FREQ_EST_L];
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memcpy(unwrapped_phase_history, phase_history, sizeof(unwrapped_phase_history));
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liquid_unwrap_phase(unwrapped_phase_history, FREQ_EST_L);
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// calculate slope of LMS-fitted line
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float mean_index = (FREQ_EST_L-1) / 2.0f;
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float mean_phase = 0.0f;
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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mean_phase += unwrapped_phase_history[j];
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}
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mean_phase /= FREQ_EST_L;
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float numerator = 0.0f;
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float denominator = 0.0f;
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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float delta_index = j - mean_index;
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numerator += delta_index * (unwrapped_phase_history[j] - mean_phase);
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denominator += delta_index*delta_index;
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}
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float lms_phase_change = numerator / denominator;
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float freq_adjustment = (lms_phase_change / RRC_SPS / 2) * 0.3f;
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nco_crcf_adjust_frequency(carrier_nco, freq_adjustment);
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printf("Frequency adjustment: %.6f - carrier frequency: %.6f\n", freq_adjustment, nco_crcf_get_frequency(carrier_nco));
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if(i/RRC_SPS == 2*FREQ_EST_L) {
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float complex tmp[FREQ_EST_L];
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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tmp[j] = unwrapped_phase_history[j];
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}
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dump_array_cf(tmp, FREQ_EST_L, 1.0f, "/tmp/freq_est.cpx");
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printf("MARK\n");
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}
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}
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}
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break;
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case RX_STATE_HEADER:
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case RX_STATE_DATA:
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break;
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}
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// preamble search
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if(out_len != 0) {
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if(out_len != 0) {
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float complex corr_out = correlator_step(&preamble_correlator, symsync_out[symsync_out_len]);
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float complex corr_out;
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switch(rx_state) {
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// Try to acquire packets by synchronizing the frequency
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// (symbol-independent search) and correlating the preamble.
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case RX_STATE_ACQUISITION:
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// preamble search
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corr_out = correlator_step(&preamble_correlator, symsync_out[symsync_out_len]);
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if(cabsf(corr_out) > 0.5f * preamble_get_symbol_count()) {
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if(cabsf(corr_out) > 0.5f * preamble_get_symbol_count()) {
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printf("Preamble found at sample %u: %.3f > %.3f\n", i/RRC_SPS, cabsf(corr_out), 0.5f * preamble_get_symbol_count());
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// Preamble found!
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printf("Preamble found at symbol %u: %.3f > %.3f\n", i/RRC_SPS, cabsf(corr_out), 0.5f * preamble_get_symbol_count());
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float mean_phase_error = correlator_get_mean_phase_deviation(&preamble_correlator);
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float mean_frequency_error = correlator_get_mean_frequency_deviation(&preamble_correlator);
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printf("Preamble phase deviation: %.6f rad\n", mean_phase_error);
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printf("Preamble frequency deviation: %.6f rad/symbol\n", mean_frequency_error);
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// adjust the frequency and phase of the NCO with the estimations from the preamble
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nco_crcf_adjust_frequency(carrier_nco, -mean_frequency_error / RRC_SPS);
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nco_crcf_adjust_phase(carrier_nco, mean_phase_error);
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printf("New estimated carrier frequency: %.6f\n", nco_crcf_get_frequency(carrier_nco));
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float complex input_history[preamble_get_symbol_count()];
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correlator_get_input_history(&preamble_correlator, input_history);
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printf("import numpy as np\n");
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printf("import matplotlib.pyplot as pp\n");
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print_complex_array("pre", preamble_get_symbols(), preamble_get_symbol_count());
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print_complex_array("recv", input_history, preamble_get_symbol_count());
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printf("pp.plot(recv * pre.conj())\n");
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printf("pp.show()\n");
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// receive and decode the header
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rx_state = RX_STATE_HEADER;
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} else {
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// preamble not found.
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// for all the output samples produced, run the frequency
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// estimator. This is an implementation that works with unknown
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// BPSK symbols and therefore can be used during ramp-up and
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// preamble.
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if(out_len < FREQ_EST_L) {
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memmove(phase_history,
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phase_history + out_len,
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(FREQ_EST_L-out_len) * sizeof(phase_history[0]));
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}
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for(unsigned int j = 0; j < out_len; j++) {
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float complex *psymbol = symsync_out + symsync_out_len + j;
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// square the symbol to remove BPSK ambiguity
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float phase = cargf((*psymbol) * (*psymbol));
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phase_history[FREQ_EST_L - out_len + j] = phase;
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}
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// update the frequency estimate
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if(((i/RRC_SPS) % FREQ_EST_L) == 0) {
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float unwrapped_phase_history[FREQ_EST_L];
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memcpy(unwrapped_phase_history, phase_history, sizeof(unwrapped_phase_history));
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liquid_unwrap_phase(unwrapped_phase_history, FREQ_EST_L);
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// calculate slope of LMS-fitted line
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float mean_index = (FREQ_EST_L-1) / 2.0f;
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float mean_phase = 0.0f;
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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mean_phase += unwrapped_phase_history[j];
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}
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mean_phase /= FREQ_EST_L;
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float numerator = 0.0f;
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float denominator = 0.0f;
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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float delta_index = j - mean_index;
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numerator += delta_index * (unwrapped_phase_history[j] - mean_phase);
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denominator += delta_index*delta_index;
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}
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float lms_phase_change = numerator / denominator;
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float freq_adjustment = (lms_phase_change / RRC_SPS / 2) * 0.5f;
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nco_crcf_adjust_frequency(carrier_nco, freq_adjustment);
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printf("Frequency adjustment: %.6f - carrier frequency: %.6f\n", freq_adjustment, nco_crcf_get_frequency(carrier_nco));
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if(i/RRC_SPS == 2*FREQ_EST_L) {
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float complex tmp[FREQ_EST_L];
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for(unsigned int j = 0; j < FREQ_EST_L; j++) {
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tmp[j] = unwrapped_phase_history[j];
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}
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dump_array_cf(tmp, FREQ_EST_L, 1.0f, "/tmp/freq_est.cpx");
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printf("MARK\n");
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}
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}
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}
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break;
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case RX_STATE_HEADER:
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case RX_STATE_DATA:
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break;
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}
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}
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}
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}
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