mirror/rtl_433
1
0
Fork 0
mirror of https://github.com/merbanan/rtl_433.git synced 2026-04-23 02:57:07 -04:00
Code Issues Packages Projects Releases Wiki Activity

Add heuristic for detecting RFM01-framed FSK

Browse Source
This commit is contained in:
David Woodhouse
2015-12-07 14:31:01 +00:00
parent a75ed5ab6f
commit 712f97e4ef
1 changed files with 40 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
src/pulse_detect.c
View File

@@ -335,6 +335,40 @@ void histogram_print(const histogram_t *hist) {
#define TOLERANCE (0.2) // 20% tolerance should still discern between the pulse widths: 0.33, 0.66, 1.0
// Detecting the RFM01/Si4320 framed FSK is non-trivial so do it in a separate function
static int detect_framed_fsk(histogram_t *hist_pulses, histogram_t *hist_gaps, pulse_data_t *data)
{
unsigned halfbit;
// It is theoretically possible for a valid data packet to contain
// no double-halfbit pulses, or no single-halfbit pulses, if the
// packet is either *all* zeroes or repeated 010101, respectively.
// As long the actual devices decoders *will* work for this unlikely
// case, it's probably OK for the heuristic not to guess it. This
// function is fun enough already without coping with that...
if (hist_pulses->bins_count < 3 || hist_gaps->bins_count < 3)
return 0;
// We use the gaps not the pulses because we *consistently* see
// a misdetected pulse of a few (5 or 6) samples, after a frame
// ends with a low frequency (i.e. last data bit is a 0). See
// discussion in Issue #218.
halfbit = min(hist_gaps->bins[0].mean, hist_gaps->bins[1].mean);
// Start of frame must be 3 halfbits high, followed by 3 or 4 low.
if (data->pulse[0] < halfbit * 5/2 || data->pulse[0] > halfbit * 7/2 ||
data->gap[0] < halfbit * 5/2 || data->gap[0] > halfbit * 9/2)
return 0;
// We could do a lot here, to the extent of a full decoding to check
// the framing. That doesn't seem necessary, as long as we don't have
// too many false positives. This is just a heuristic, after all.
if (hist_gaps->bins[2].mean < halfbit * 5/2)
return 0;
return 1;
}
/// Analyze the statistics of a pulse data structure and print result
void pulse_analyzer(pulse_data_t *data)
{
@@ -400,6 +434,12 @@ void pulse_analyzer(pulse_data_t *data)
device.short_limit = min(hist_pulses.bins[0].mean, hist_pulses.bins[1].mean); // Assume shortest pulse is half period
device.long_limit = 0; // Not used
device.reset_limit = hist_gaps.bins[hist_gaps.bins_count-1].max + 1; // Set limit above biggest gap
} else if(detect_framed_fsk(&hist_pulses, &hist_gaps, data)) {
fprintf(stderr, "RFM Framed Manchester coding\n");
device.modulation = FSK_PULSE_MANCHESTER_FRAMED;
device.short_limit = min(hist_gaps.bins[0].mean, hist_gaps.bins[1].mean); // Assume shortest pulse is half period
device.long_limit = 0; // Not used
device.reset_limit = 0; // Not used
} else if(hist_pulses.bins_count == 3) {
fprintf(stderr, "Pulse Width Modulation with startbit/delimiter\n");
device.modulation = OOK_PULSE_PWM_TERNARY;