// Help function to keep code base small
// _kf : modulation factor
// _type : demodulation type {LIQUID_FREQDEM_DELAYCONJ, LIQUID_FREQDEM_PLL}
void freqmodem_test(float _kf,
liquid_freqdem_type _type)
{
// options
unsigned int num_samples = 1024;
//float tol = 1e-2f;
unsigned int i;
// create mod/demod objects
freqmod mod = freqmod_create(_kf); // modulator
freqdem dem = freqdem_create(_kf,_type); // demodulator
// allocate arrays
float m[num_samples]; // message signal
float complex r[num_samples]; // received signal (complex baseband)
float y[num_samples]; // demodulator output
// generate message signal (single-frequency sine)
for (i=0; i<num_samples; i++)
m[i] = 0.7f*cosf(2*M_PI*0.013f*i + 0.0f);
// modulate/demodulate signal
for (i=0; i<num_samples; i++) {
// modulate
freqmod_modulate(mod, m[i], &r[i]);
// demodulate
freqdem_demodulate(dem, r[i], &y[i]);
}
// delete modem objects
freqmod_destroy(mod);
freqdem_destroy(dem);
#if 0
// compute power spectral densities and compare
float complex mcf[num_samples];
float complex ycf[num_samples];
float complex M[num_samples];
float complex Y[num_samples];
for (i=0; i<num_samples; i++) {
mcf[i] = m[i] * hamming(i,num_samples);
ycf[i] = y[i] * hamming(i,num_samples);
}
fft_run(num_samples, mcf, M, LIQUID_FFT_FORWARD, 0);
fft_run(num_samples, ycf, Y, LIQUID_FFT_FORWARD, 0);
// run test: compare spectral magnitude
for (i=0; i<num_samples; i++)
CONTEND_DELTA( cabsf(Y[i]), cabsf(M[i]), tol );
#endif
}
// frequency demodulator benchmark
void benchmark_freqdem(struct rusage * _start,
struct rusage * _finish,
unsigned long int * _num_iterations)
{
// create demodulator
float kf = 0.05f; // modulation index
freqdem dem = freqdem_create(kf);
float complex r[20]; // modulated signal
float m[20]; // message signal
unsigned long int i;
// generate modulated signal
for (i=0; i<20; i++)
r[i] = 0.3f*cexpf(_Complex_I*2*M_PI*i/20.0f);
// start trials
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
freqdem_demodulate(dem, r[ 0], &m[ 0]);
freqdem_demodulate(dem, r[ 1], &m[ 1]);
freqdem_demodulate(dem, r[ 2], &m[ 2]);
freqdem_demodulate(dem, r[ 3], &m[ 3]);
freqdem_demodulate(dem, r[ 4], &m[ 4]);
freqdem_demodulate(dem, r[ 5], &m[ 5]);
freqdem_demodulate(dem, r[ 6], &m[ 6]);
freqdem_demodulate(dem, r[ 7], &m[ 7]);
freqdem_demodulate(dem, r[ 8], &m[ 8]);
freqdem_demodulate(dem, r[ 9], &m[ 9]);
freqdem_demodulate(dem, r[10], &m[10]);
freqdem_demodulate(dem, r[11], &m[11]);
freqdem_demodulate(dem, r[12], &m[12]);
freqdem_demodulate(dem, r[13], &m[13]);
freqdem_demodulate(dem, r[14], &m[14]);
freqdem_demodulate(dem, r[15], &m[15]);
freqdem_demodulate(dem, r[16], &m[16]);
freqdem_demodulate(dem, r[17], &m[17]);
freqdem_demodulate(dem, r[18], &m[18]);
freqdem_demodulate(dem, r[19], &m[19]);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 20;
// destroy demodulator
freqdem_destroy(dem);
}
ModemNBFM::ModemNBFM() : ModemAnalog() {
demodFM = freqdem_create(0.5);
}
ModemFMStereo::ModemFMStereo() {
demodFM = freqdem_create(0.5);
_demph = 75;
}
// main program
int main (int argc, char **argv)
{
// command-line options
int verbose = 1;
int ppm_error = 0;
int gain = 0;
float rx_resamp_rate;
float bandwidth = 800e3f;
int r, n_read;
uint32_t frequency = 100000000;
uint32_t samp_rate = DEFAULT_SAMPLE_RATE;
uint32_t out_block_size = DEFAULT_BUF_LENGTH;
uint8_t *buffer;
complex float *buffer_norm;
int dev_index = 0;
int dev_given = 0;
struct sigaction sigact;
normalizer_t *norm;
float kf = 0.1f; // modulation factor
liquid_freqdem_type type = LIQUID_FREQDEM_DELAYCONJ;
//
int d;
while ((d = getopt(argc,argv,"hf:b:B:G:p:s:")) != EOF) {
switch (d) {
case 'h': usage(); return 0;
case 'f': frequency = atof(optarg); break;
case 'b': bandwidth = atof(optarg); break;
case 'B': out_block_size = (uint32_t)atof(optarg); break;
case 'G': gain = (int)(atof(optarg) * 10); break;
case 'p': ppm_error = atoi(optarg); break;
case 's': samp_rate = (uint32_t)atofs(optarg); break;
case 'd':
dev_index = verbose_device_search(optarg);
dev_given = 1;
break;
default: usage(); return 1;
}
}
if (!dev_given) {
dev_index = verbose_device_search("0");
}
if (dev_index < 0) {
exit(1);
}
r = rtlsdr_open(&dev, (uint32_t)dev_index);
if (r < 0) {
fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dev_index);
exit(1);
}
sigact.sa_handler = sighandler;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = 0;
sigaction(SIGINT, &sigact, NULL);
sigaction(SIGTERM, &sigact, NULL);
sigaction(SIGQUIT, &sigact, NULL);
sigaction(SIGPIPE, &sigact, NULL);
/* Set the sample rate */
verbose_set_sample_rate(dev, samp_rate);
/* Set the frequency */
verbose_set_frequency(dev, frequency);
if (0 == gain) {
/* Enable automatic gain */
verbose_auto_gain(dev);
} else {
/* Enable manual gain */
gain = nearest_gain(dev, gain);
verbose_gain_set(dev, gain);
}
verbose_ppm_set(dev, ppm_error);
rx_resamp_rate = bandwidth/samp_rate;
printf("frequency : %10.4f [MHz]\n", frequency*1e-6f);
printf("bandwidth : %10.4f [kHz]\n", bandwidth*1e-3f);
printf("sample rate : %10.4f kHz = %10.4f kHz * %8.6f\n",
samp_rate * 1e-3f,
bandwidth * 1e-3f,
1.0f / rx_resamp_rate);
printf("verbosity : %s\n", (verbose?"enabled":"disabled"));
unsigned int i,j;
// add arbitrary resampling component
msresamp_crcf resamp = msresamp_crcf_create(rx_resamp_rate, 60.0f);
assert(resamp);
//allocate recv buffer
buffer = malloc(out_block_size * sizeof(uint8_t));
assert(buffer);
buffer_norm = malloc(out_block_size * sizeof(complex float));
assert(buffer_norm);
// create buffer for arbitrary resamper output
int b_len = ((int)(out_block_size * rx_resamp_rate) + 64) >> 1;
complex float buffer_resamp[b_len];
int16_t buffer_demod[b_len];
debug("resamp_buffer_len: %d\n", b_len);
norm = normalizer_create();
verbose_reset_buffer(dev);
freqdem dem = freqdem_create(kf,type);
while (!do_exit) {
// grab data from device
r = rtlsdr_read_sync(dev, buffer, out_block_size, &n_read);
if (r < 0) {
fprintf(stderr, "WARNING: sync read failed.\n");
break;
}
if ((bytes_to_read > 0) && (bytes_to_read < (uint32_t)n_read)) {
n_read = bytes_to_read;
do_exit = 1;
}
// push data through arbitrary resampler and give to frame synchronizer
// TODO : apply bandwidth-dependent gain
for (i=0; i<n_read/2; i++) {
// grab sample from usrp buffer
buffer_norm[i] = normalizer_normalize(norm, *((uint16_t*)buffer+i));
}
// push through resampler (one at a time)
unsigned int nw;
float demod;
msresamp_crcf_execute(resamp, buffer_norm, n_read/2, buffer_resamp, &nw);
for(j=0;j<nw;j++)
{
freqdem_demodulate(dem, buffer_resamp[j], &demod);
buffer_demod[j] = to_int16(demod);
}
if (fwrite(buffer_demod, 2, nw, stdout) != (size_t)nw) {
fprintf(stderr, "Short write, samples lost, exiting!\n");
break;
}
if ((uint32_t)n_read < out_block_size) {
fprintf(stderr, "Short read, samples lost, exiting!\n");
break;
}
if (bytes_to_read > 0)
bytes_to_read -= n_read;
}
// destroy objects
freqdem_destroy(dem);
normalizer_destroy(&norm);
msresamp_crcf_destroy(resamp);
rtlsdr_close(dev);
free (buffer);
return 0;
}