2015-11-16 23:49:54 -05:00
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#include "ModemUSB.h"
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2015-11-28 23:03:07 -05:00
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ModemUSB::ModemUSB() : ModemAnalog() {
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2015-11-16 23:49:54 -05:00
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// half band filter used for side-band elimination
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demodAM_USB = ampmodem_create(0.5, 0.0, LIQUID_AMPMODEM_USB, 1);
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2016-01-10 16:22:19 -05:00
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// options
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float fc = 0.25f; // filter cutoff frequency
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float ft = 0.05f; // filter transition
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float As = 90.0f; // stop-band attenuation [dB]
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float mu = 0.0f; // fractional timing offset
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// estimate required filter length and generate filter
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unsigned int h_len = estimate_req_filter_len(ft,As);
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2016-01-22 20:26:22 -05:00
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float *h = (float *) malloc(h_len * sizeof(float));
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2016-01-10 16:22:19 -05:00
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liquid_firdes_kaiser(h_len,fc,As,mu,h);
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ssbFilt = firfilt_crcf_create(h,h_len);
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ssbShift = nco_crcf_create(LIQUID_NCO);
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nco_crcf_set_frequency(ssbShift, (2.0 * M_PI) * 0.25);
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2016-01-22 20:26:22 -05:00
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free(h);
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2015-11-16 23:49:54 -05:00
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}
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Modem *ModemUSB::factory() {
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return new ModemUSB;
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}
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2015-11-18 23:40:30 -05:00
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std::string ModemUSB::getName() {
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return "USB";
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}
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2015-11-16 23:49:54 -05:00
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ModemUSB::~ModemUSB() {
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2016-01-10 16:22:19 -05:00
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firfilt_crcf_destroy(ssbFilt);
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nco_crcf_destroy(ssbShift);
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2015-11-16 23:49:54 -05:00
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ampmodem_destroy(demodAM_USB);
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}
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2015-11-22 19:56:25 -05:00
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int ModemUSB::checkSampleRate(long long sampleRate, int audioSampleRate) {
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2015-12-01 00:59:11 -05:00
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if (sampleRate < MIN_BANDWIDTH) {
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return MIN_BANDWIDTH;
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2015-11-22 23:38:26 -05:00
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}
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2015-11-22 19:56:25 -05:00
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if (sampleRate % 2 == 0) {
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return sampleRate;
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}
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return sampleRate+1;
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}
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2015-11-30 21:58:54 -05:00
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int ModemUSB::getDefaultSampleRate() {
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return 5400;
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}
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2015-11-16 23:49:54 -05:00
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void ModemUSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
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ModemKitAnalog *akit = (ModemKitAnalog *)kit;
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initOutputBuffers(akit,input);
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if (!bufSize) {
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input->decRefCount();
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return;
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}
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liquid_float_complex x, y;
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for (int i = 0; i < bufSize; i++) { // Reject lower band
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2016-01-10 16:22:19 -05:00
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nco_crcf_step(ssbShift);
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nco_crcf_mix_down(ssbShift, input->data[i], &x);
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firfilt_crcf_push(ssbFilt, x);
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firfilt_crcf_execute(ssbFilt, &x);
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nco_crcf_mix_up(ssbShift, x, &y);
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2015-11-16 23:49:54 -05:00
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ampmodem_demodulate(demodAM_USB, y, &demodOutputData[i]);
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}
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buildAudioOutput(akit, audioOut, true);
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}
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