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hackrf_sweep: eliminate time stamp adjustment

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We previously attempted to adjust the output time stamp according to the
sample rate and placement of the samples within the USB transfer data,
but the end result was a fixed time offset with respect to the time of
USB transfer completion. We are using only those samples closest to the
end of the transfer, so it makes sense to simply use the time the USB
transfer ends and not try to correct that fixed offset.

It may be possible in the future to have a more accurate time stamp
generated in firmware, but I don't think it is worth complicating the
host code with minor time adjustments until and unless firmware-based
time stamps become available.
This commit is contained in:
Michael Ossmann
2021-11-14 11:20:31 -07:00
parent bd4b786136
commit 2775279fd0
1 changed files with 3 additions and 12 deletions
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15
host/hackrf-tools/src/hackrf_sweep.c
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@ -171,7 +171,6 @@ volatile uint64_t sweep_count = 0;
struct timeval time_start; struct timeval time_start;
struct timeval t_start; struct timeval t_start;
struct timeval time_stamp;
bool amp = false; bool amp = false;
uint32_t amp_enable; uint32_t amp_enable;
@ -257,14 +256,6 @@ int rx_callback(hackrf_transfer* transfer) {
} }
} }
sweep_started = true; sweep_started = true;
time_stamp = usb_transfer_time;
time_stamp.tv_usec +=
(uint64_t)(num_samples + THROWAWAY_BLOCKS * SAMPLES_PER_BLOCK)
* j * FREQ_ONE_MHZ / DEFAULT_SAMPLE_RATE_HZ;
if(999999 < time_stamp.tv_usec) {
time_stamp.tv_sec += time_stamp.tv_usec / 1000000;
time_stamp.tv_usec = time_stamp.tv_usec % 1000000;
}
} }
if(do_exit) { if(do_exit) {
return 0; return 0;
@ -320,12 +311,12 @@ int rx_callback(hackrf_transfer* transfer) {
ifftwIn[ifft_idx + i][1] = fftwOut[i + 1 + (fftSize/8)][1]; ifftwIn[ifft_idx + i][1] = fftwOut[i + 1 + (fftSize/8)][1];
} }
} else { } else {
time_t time_stamp_seconds = time_stamp.tv_sec; time_t time_stamp_seconds = usb_transfer_time.tv_sec;
fft_time = localtime(&time_stamp_seconds); fft_time = localtime(&time_stamp_seconds);
strftime(time_str, 50, "%Y-%m-%d, %H:%M:%S", fft_time); strftime(time_str, 50, "%Y-%m-%d, %H:%M:%S", fft_time);
fprintf(outfile, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u", fprintf(outfile, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u",
time_str, time_str,
(long int)time_stamp.tv_usec, (long int)usb_transfer_time.tv_usec,
(uint64_t)(frequency), (uint64_t)(frequency),
(uint64_t)(frequency+DEFAULT_SAMPLE_RATE_HZ/4), (uint64_t)(frequency+DEFAULT_SAMPLE_RATE_HZ/4),
fft_bin_width, fft_bin_width,
@ -336,7 +327,7 @@ int rx_callback(hackrf_transfer* transfer) {
fprintf(outfile, "\n"); fprintf(outfile, "\n");
fprintf(outfile, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u", fprintf(outfile, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u",
time_str, time_str,
(long int)time_stamp.tv_usec, (long int)usb_transfer_time.tv_usec,
(uint64_t)(frequency+(DEFAULT_SAMPLE_RATE_HZ/2)), (uint64_t)(frequency+(DEFAULT_SAMPLE_RATE_HZ/2)),
(uint64_t)(frequency+((DEFAULT_SAMPLE_RATE_HZ*3)/4)), (uint64_t)(frequency+((DEFAULT_SAMPLE_RATE_HZ*3)/4)),
fft_bin_width, fft_bin_width,