FGFS-4.1/gr-air-modes
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Split the int timestamp from frac timestamp so you don't lose precision when using, say, UTC time. Cleaned up some cruft while I was at it. This also allows devices which don't have timestamps to tag based on samples elapsed since the flowgraph started.

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This commit is contained in:
Nick Foster
2012-12-12 17:40:35 -08:00
parent 3be6e9fd6e
commit 1e2b8a4f46
9 changed files with 68 additions and 76 deletions
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lib/air_modes_preamble.cc
+27 -18
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@@ -78,20 +78,31 @@ static double correlate_preamble(const float *in, int samples_per_chip) {
return corr;
}
//todo: make it return a pair of some kind, otherwise you can lose precision
static double tag_to_timestamp(gr_tag_t tstamp, uint64_t abs_sample_cnt, double secs_per_sample) {
//takes an rx tag and issues a tag offset appropriately for the preamble
static const pmt::pmt_t offset_stamp(const gr_tag_t &tstamp, const uint64_t abs_sample_cnt, const double secs_per_sample) {
uint64_t ts_sample, last_whole_stamp;
double last_frac_stamp;
if(tstamp.key == NULL || pmt::pmt_symbol_to_string(tstamp.key) != "rx_time") return 0;
last_whole_stamp = pmt::pmt_to_uint64(pmt::pmt_tuple_ref(tstamp.value, 0));
last_frac_stamp = pmt::pmt_to_double(pmt::pmt_tuple_ref(tstamp.value, 1));
ts_sample = tstamp.offset;
if(tstamp.key == NULL || pmt::pmt_symbol_to_string(tstamp.key) != "rx_time") {
last_whole_stamp = 0;
last_frac_stamp = 0;
ts_sample = 0;
} else {
last_whole_stamp = pmt::pmt_to_uint64(pmt::pmt_tuple_ref(tstamp.value, 0));
last_frac_stamp = pmt::pmt_to_double(pmt::pmt_tuple_ref(tstamp.value, 1));
ts_sample = tstamp.offset;
}
double tstime = double(abs_sample_cnt * secs_per_sample) + last_whole_stamp + last_frac_stamp;
if(0) std::cout << "HEY WE GOT A STAMP AT " << tstime << " TICKS AT SAMPLE " << ts_sample << " ABS SAMPLE CNT IS " << abs_sample_cnt << std::endl;
return tstime;
double fractime = double(abs_sample_cnt * secs_per_sample) + last_frac_stamp;
last_whole_stamp += int(fractime);
fractime -= int(fractime);
const pmt::pmt_t newval = pmt::pmt_make_tuple(
pmt::pmt_from_uint64(last_whole_stamp),
pmt::pmt_from_double(fractime)
);
return newval;
}
int air_modes_preamble::general_work(int noutput_items,
@@ -186,16 +197,14 @@ int air_modes_preamble::general_work(int noutput_items,
integrate_and_dump(out, &in[i], 240, d_samples_per_chip);
}
//get the timestamp of the preamble
double tstamp = tag_to_timestamp(d_timestamp, abs_sample_cnt + i, d_secs_per_sample);
const pmt::pmt_t new_pmt = offset_stamp(d_timestamp, abs_sample_cnt + i, d_secs_per_sample);
//now tag the preamble
add_item_tag(0, //stream ID
nitems_written(0), //sample
d_key, //frame_info
pmt::pmt_from_double(tstamp),
d_me //block src id
);
nitems_written(0), //sample
d_key, //frame_info
new_pmt,
d_me //block src id
);
//std::cout << "PREAMBLE" << std::endl;