From 5f1d7bc9705cf31f55cd802ba616f42a92da3618 Mon Sep 17 00:00:00 2001 From: Andreas Eversberg Date: Wed, 1 Feb 2017 17:57:09 +0100 Subject: C-Netz: Improve clock speed measurements. Sound card's clock measurements only requires a few minutes to get sub-ppm accuracy results. --- src/cnetz/dsp.c | 60 +++++++++++++++++++++++---------------------------------- 1 file changed, 24 insertions(+), 36 deletions(-) (limited to 'src/cnetz/dsp.c') diff --git a/src/cnetz/dsp.c b/src/cnetz/dsp.c index e47bd7a..84b6a30 100644 --- a/src/cnetz/dsp.c +++ b/src/cnetz/dsp.c @@ -195,19 +195,17 @@ void dsp_cleanup_sender(cnetz_t *cnetz) /* receive sample time and calculate speed against system clock * tx: indicates transmit stream * result: if set the actual signal speed is used (instead of sample rate) */ -void calc_clock_speed(cnetz_t *cnetz, uint64_t samples, int tx, int result) +void calc_clock_speed(cnetz_t *cnetz, double samples, int tx, int result) { struct clock_speed *cs = &cnetz->clock_speed; double ti; - double speed_ppm_rx_avg[2], speed_ppm_tx_avg[2]; + double speed_ppm_avg[4]; + int index = (result << 1) | tx; int i; if (!cnetz->measure_speed) return; - if (result) - tx += 2; - ti = get_time(); /* skip some time to avoid false mesurement due to filling of buffers */ @@ -219,46 +217,36 @@ void calc_clock_speed(cnetz_t *cnetz, uint64_t samples, int tx, int result) return; /* start sample counting */ - if (cs->start_ti[tx] == 0.0) { - cs->start_ti[tx] = ti; - cs->spl_count[tx] = 0; + if (cs->start_ti[index] == 0.0) { + cs->start_ti[index] = ti; + cs->spl_count[index] = 0.0; return; } /* add elapsed time */ - cs->last_ti[tx] = ti; - cs->spl_count[tx] += samples; + cs->last_ti[index] = ti; + cs->spl_count[index] += samples; /* only calculate speed, if one second has elapsed */ - if (ti - cs->meas_ti <= 1.0) + if (ti - cs->meas_ti <= 2.0) return; - cs->meas_ti += 1.0; + cs->meas_ti += 2.0; - if (!cs->spl_count[2] || !cs->spl_count[3]) + /* add to ring buffer */ + if (!cs->spl_count[0] || !cs->spl_count[1] || !cs->spl_count[2] || !cs->spl_count[3]) return; - cs->speed_ppm_rx[0][cs->idx & 0xff] = ((double)cs->spl_count[0] / (double)cnetz->sender.samplerate) / (cs->last_ti[0] - cs->start_ti[0]) * 1000000.0 - 1000000.0; - cs->speed_ppm_tx[0][cs->idx & 0xff] = ((double)cs->spl_count[1] / (double)cnetz->sender.samplerate) / (cs->last_ti[1] - cs->start_ti[1]) * 1000000.0 - 1000000.0; - cs->speed_ppm_rx[1][cs->idx & 0xff] = ((double)cs->spl_count[2] / (double)cnetz->sender.samplerate) / (cs->last_ti[2] - cs->start_ti[2]) * 1000000.0 - 1000000.0; - cs->speed_ppm_tx[1][cs->idx & 0xff] = ((double)cs->spl_count[3] / (double)cnetz->sender.samplerate) / (cs->last_ti[3] - cs->start_ti[3]) * 1000000.0 - 1000000.0; - cs->idx++; - cs->num++; - if (cs->num > 30) - cs->num = 30; - speed_ppm_rx_avg[0] = 0.0; - speed_ppm_tx_avg[0] = 0.0; - speed_ppm_rx_avg[1] = 0.0; - speed_ppm_tx_avg[1] = 0.0; - for (i = 0; i < cs->num; i++) { - speed_ppm_rx_avg[0] += cs->speed_ppm_rx[0][(cs->idx - i - 1) & 0xff]; - speed_ppm_tx_avg[0] += cs->speed_ppm_tx[0][(cs->idx - i - 1) & 0xff]; - speed_ppm_rx_avg[1] += cs->speed_ppm_rx[1][(cs->idx - i - 1) & 0xff]; - speed_ppm_tx_avg[1] += cs->speed_ppm_tx[1][(cs->idx - i - 1) & 0xff]; + + for (index = 0; index < 4; index++) { + cs->speed_ppm[index][cs->idx[index] & 0xff] = (cs->spl_count[index] / (double)cnetz->sender.samplerate) / (cs->last_ti[index] - cs->start_ti[index]) * 1000000.0 - 1000000.0; + cs->idx[index]++; + if (cs->num[index]++ > 30) + cs->num[index] = 30; + speed_ppm_avg[index] = 0.0; + for (i = 0; i < cs->num[index]; i++) + speed_ppm_avg[index] += cs->speed_ppm[index][(cs->idx[index] - i - 1) & 0xff]; + speed_ppm_avg[index] /= (double)cs->num[index]; } - speed_ppm_rx_avg[0] /= (double)cs->num; - speed_ppm_tx_avg[0] /= (double)cs->num; - speed_ppm_rx_avg[1] /= (double)cs->num; - speed_ppm_tx_avg[1] /= (double)cs->num; - PDEBUG_CHAN(DDSP, DEBUG_NOTICE, "Clock: RX=%.2f TX=%.2f; Signal: RX=%.2f TX=%.2f ppm\n", speed_ppm_rx_avg[0], speed_ppm_tx_avg[0], speed_ppm_rx_avg[1], speed_ppm_tx_avg[1]); + PDEBUG_CHAN(DDSP, DEBUG_NOTICE, "Clock: RX=%.3f TX=%.3f; Signal: RX=%.3f TX=%.3f ppm\n", speed_ppm_avg[0], speed_ppm_avg[1], speed_ppm_avg[2], speed_ppm_avg[3]); } static int fsk_testtone_encode(cnetz_t *cnetz) @@ -622,7 +610,7 @@ again: /* a new hyper frame starts */ if (cnetz->sched_ts == 0 && cnetz->sched_r_m == 0) { /* measure actual signal speed */ - calc_clock_speed(cnetz, cnetz->sender.samplerate * 24 / 10, 1, 1); + calc_clock_speed(cnetz, (double)cnetz->sender.samplerate * 2.4, 1, 1); /* sync TX (might not be required, if there is no error in math calculation) */ if (!cnetz->sender.master) { /* if no link to a master, we are master */ /* we are master, so we store sample count and phase */ -- cgit v1.2.3