// reset frame synchronizer object
void flexframesync_reset(flexframesync _q)
{
// reset binary pre-demod synchronizer
detector_cccf_reset(_q->frame_detector);
// clear pre-demod buffer
windowcf_clear(_q->buffer);
// reset carrier recovery objects
nco_crcf_reset(_q->nco_coarse);
nco_crcf_reset(_q->nco_fine);
// reset symbol timing recovery state
firpfb_crcf_reset(_q->mf);
firpfb_crcf_reset(_q->dmf);
_q->pfb_q = 0.0f; // filtered error signal
// reset state
_q->state = STATE_DETECTFRAME;
_q->pn_counter = 0;
_q->header_counter = 0;
_q->payload_counter = 0;
// reset frame statistics
_q->framestats.evm = 0.0f;
}
// push buffered p/n sequence through synchronizer
void flexframesync_pushpn(flexframesync _q)
{
unsigned int i;
// reset filterbanks
firpfb_crcf_reset(_q->mf);
firpfb_crcf_reset(_q->dmf);
// read buffer
float complex * rc;
windowcf_read(_q->buffer, &rc);
// compute delay and filterbank index
// tau_hat < 0 : delay = 2*k*m-1, index = round( tau_hat *npfb), flag = 0
// tau_hat > 0 : delay = 2*k*m-2, index = round((1-tau_hat)*npfb), flag = 0
assert(_q->tau_hat < 0.5f && _q->tau_hat > -0.5f);
unsigned int delay = 2*_q->k*_q->m - 1; // samples to buffer before computing output
_q->pfb_soft = -_q->tau_hat*_q->npfb;
_q->pfb_index = (int) roundf(_q->pfb_soft);
while (_q->pfb_index < 0) {
delay -= 1;
_q->pfb_index += _q->npfb;
_q->pfb_soft += _q->npfb;
}
_q->pfb_timer = 0;
// set coarse carrier frequency offset
nco_crcf_set_frequency(_q->nco_coarse, _q->dphi_hat);
unsigned int buffer_len = (64+_q->m)*_q->k;
for (i=0; i<buffer_len; i++) {
if (i < delay) {
float complex y;
nco_crcf_mix_down(_q->nco_coarse, rc[i]*0.5f/_q->gamma_hat, &y);
nco_crcf_step(_q->nco_coarse);
// push initial samples into filterbanks
firpfb_crcf_push(_q->mf, y);
firpfb_crcf_push(_q->dmf, y);
} else {
// run remaining samples through p/n sequence recovery
flexframesync_execute_rxpn(_q, rc[i]);
}
}
// set state (still need a few more samples before entire p/n
// sequence has been received)
_q->state = STATE_RXPN;
}
// reset frame synchronizer object
void flexframesync_reset(flexframesync _q)
{
// reset binary pre-demod synchronizer
qdetector_cccf_reset(_q->detector);
// reset carrier recovery objects
nco_crcf_reset(_q->mixer);
nco_crcf_reset(_q->pll);
// reset symbol timing recovery state
firpfb_crcf_reset(_q->mf);
// reset state
_q->state = FLEXFRAMESYNC_STATE_DETECTFRAME;
_q->preamble_counter= 0;
_q->symbol_counter = 0;
// reset frame statistics
_q->framesyncstats.evm = 0.0f;
}