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Add syncword fuzzy detection 

Frame decoder now tolerates bit error in syncword, removed syncword type
detection in demodulator code.

TG-81
This commit is contained in:
Niccolò Izzo 2022-05-10 11:18:21 +02:00 committed by Silvano Seva
parent b998d3b78f
commit c3c984d504
3 changed files with 4 additions and 9 deletions
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1
openrtx/include/protocols/M17/M17Demodulator.h
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@ -145,7 +145,6 @@ private:
uint16_t frame_index; ///< Index for filling the raw frame. uint16_t frame_index; ///< Index for filling the raw frame.
frame_t *activeFrame; ///< Half frame, in demodulation. frame_t *activeFrame; ///< Half frame, in demodulation.
frame_t *idleFrame; ///< Half frame, free to be processed. frame_t *idleFrame; ///< Half frame, free to be processed.
bool isLSF; ///< Indicates that we demodualated an LSF.
bool syncDetected; ///< A syncword was detected. bool syncDetected; ///< A syncword was detected.
bool locked; ///< A syncword was correctly demodulated. bool locked; ///< A syncword was correctly demodulated.
bool newFrame; ///< A new frame has been fully decoded. bool newFrame; ///< A new frame has been fully decoded.

8
openrtx/src/protocols/M17/M17Demodulator.cpp
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@ -271,11 +271,6 @@ const frame_t& M17Demodulator::getFrame()
return *activeFrame; return *activeFrame;
} }
bool M17Demodulator::isFrameLSF()
{
return isLSF;
}
bool M17::M17Demodulator::isLocked() bool M17::M17Demodulator::isLocked()
{ {
return locked; return locked;
@ -324,7 +319,6 @@ bool M17Demodulator::update()
if (syncword.index != -1) // Valid syncword found if (syncword.index != -1) // Valid syncword found
{ {
syncDetected = true; syncDetected = true;
isLSF = syncword.lsf;
offset = syncword.index + 1; offset = syncword.index + 1;
phase = 0; phase = 0;
frame_index = 0; frame_index = 0;
@ -402,7 +396,7 @@ bool M17Demodulator::update()
lsf_syncword_bytes[1]); lsf_syncword_bytes[1]);
// Too many errors in the syncword, lock is lost // Too many errors in the syncword, lock is lost
if ((hammingSync > 1) && (hammingLsf > 1)) if ((hammingSync > 4) && (hammingLsf > 4))
{ {
syncDetected = false; syncDetected = false;
locked = false; locked = false;

4
openrtx/src/protocols/M17/M17FrameDecoder.cpp
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@ -65,7 +65,9 @@ M17FrameType M17FrameDecoder::decodeFrame(const frame_t& frame)
} }
// Stream data frame // Stream data frame
if(syncWord == STREAM_SYNC_WORD) uint8_t hd = __builtin_popcount(syncWord[0] ^ STREAM_SYNC_WORD[0])
+ __builtin_popcount(syncWord[1] ^ STREAM_SYNC_WORD[1]);
if(hd <= 4)
{ {
decodeStream(data); decodeStream(data);
return M17FrameType::STREAM; return M17FrameType::STREAM;