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fix false positive psk demod with fsk wave

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also break out new find start of modulation routine.
This commit is contained in:
marshmellow42 2017-02-21 23:00:43 -05:00
commit 34ff898553
3 changed files with 84 additions and 61 deletions
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102
common/lfdemod.c
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@ -187,6 +187,32 @@ bool onePreambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_
return false;
}
// find start of modulating data (for fsk and psk) in case of beginning noise or slow chip startup.
size_t findModStart(uint8_t dest[], size_t size, uint8_t threshold_value, uint8_t expWaveSize) {
size_t i = 0;
size_t waveSizeCnt = 0;
uint8_t thresholdCnt = 0;
bool isAboveThreshold = dest[i++] >= threshold_value;
for (; i < size-20; i++ ) {
if(dest[i] < threshold_value && isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < expWaveSize+1) break;
isAboveThreshold = false;
waveSizeCnt = 0;
} else if (dest[i] >= threshold_value && !isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < expWaveSize+1) break;
isAboveThreshold = true;
waveSizeCnt = 0;
} else {
waveSizeCnt++;
}
if (thresholdCnt > 10) break;
}
if (g_debugMode == 2) prnt("DEBUG: threshold Count reached at %u, count: %u",i, thresholdCnt);
return i;
}
//by marshmellow
//takes 1s and 0s and searches for EM410x format - output EM ID
uint8_t Em410xDecode(uint8_t *BitStream, size_t *size, size_t *startIdx, uint32_t *hi, uint64_t *lo)
@ -496,7 +522,6 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
{
size_t last_transition = 0;
size_t idx = 1;
//uint32_t maxVal=0;
if (fchigh==0) fchigh=10;
if (fclow==0) fclow=8;
//set the threshold close to 0 (graph) or 128 std to avoid static
@ -506,28 +531,8 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
size_t currSample = 0;
if ( size < 1024 ) return 0; // not enough samples
// jump to modulating data by finding the first 4 threshold crossings (or first 2 waves)
// in case you have junk or noise at the beginning of the trace...
uint8_t thresholdCnt = 0;
size_t waveSizeCnt = 0;
bool isAboveThreshold = dest[idx++] >= threshold_value;
for (; idx < size-20; idx++ ) {
if(dest[idx] < threshold_value && isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < fchigh+1) break;
isAboveThreshold = false;
waveSizeCnt = 0;
} else if (dest[idx] >= threshold_value && !isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < fchigh+1) break;
isAboveThreshold = true;
waveSizeCnt = 0;
} else {
waveSizeCnt++;
}
if (thresholdCnt > 10) break;
}
if (g_debugMode == 2) prnt("threshold Count reached at %u",idx);
//find start of modulating data in trace
idx = findModStart(dest, size, threshold_value, fchigh);
// Need to threshold first sample
if(dest[idx] < threshold_value) dest[0] = 0;
@ -1509,42 +1514,26 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
size_t numBits=0;
uint8_t curPhase = *invert;
size_t i=0, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0;
uint8_t fc=0, fullWaveLen=0, tol=1;
uint16_t errCnt=0, waveLenCnt=0;
fc = countFC(dest, *size, 0);
uint16_t fc=0, fullWaveLen=0, tol=1;
uint16_t errCnt=0, waveLenCnt=0, errCnt2=0;
fc = countFC(dest, *size, 1);
uint8_t fc2 = fc >> 8;
if (fc2 == 10) return -1; //fsk found - quit
fc = fc & 0xFF;
if (fc!=2 && fc!=4 && fc!=8) return -1;
//PrintAndLog("DEBUG: FC: %d",fc);
*clock = DetectPSKClock(dest, *size, *clock);
if (*clock == 0) return -1;
// jump to modulating data by finding the first 2 threshold crossings (or first 1 waves)
// in case you have junk or noise at the beginning of the trace...
uint8_t thresholdCnt = 0;
size_t waveSizeCnt = 0;
//find start of modulating data in trace
uint8_t threshold_value = 123; //-5
bool isAboveThreshold = dest[i++] >= threshold_value;
for (; i < *size-20; i++ ) {
if(dest[i] < threshold_value && isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < fc+1) break;
isAboveThreshold = false;
waveSizeCnt = 0;
} else if (dest[i] >= threshold_value && !isAboveThreshold) {
thresholdCnt++;
if (thresholdCnt > 2 && waveSizeCnt < fc+1) break;
isAboveThreshold = true;
waveSizeCnt = 0;
} else {
waveSizeCnt++;
}
if (thresholdCnt > 10) break;
}
if (g_debugMode == 2) prnt("DEBUG PSK: threshold Count reached at %u, count: %u",i, thresholdCnt);
i = findModStart(dest, *size, threshold_value, fc);
int avgWaveVal=0, lastAvgWaveVal=0;
waveStart = i+1;
//find first phase shift
for (; i<loopCnt; i++){
int avgWaveVal=0, lastAvgWaveVal=0;
waveStart = i;
for (; i<loopCnt; i++) {
// find peak
if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
waveEnd = i+1;
if (g_debugMode == 2) prnt("DEBUG PSK: waveEnd: %u, waveStart: %u",waveEnd, waveStart);
@ -1553,8 +1542,8 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
lastAvgWaveVal = avgWaveVal/(waveLenCnt);
firstFullWave = waveStart;
fullWaveLen=waveLenCnt;
//if average wave value is > graph 0 then it is an up wave or a 1
if (lastAvgWaveVal > threshold_value) curPhase ^= 1; //fudge graph 0 a little 123 vs 128
//if average wave value is > graph 0 then it is an up wave or a 1 (could cause inverting)
if (lastAvgWaveVal > threshold_value) curPhase ^= 1;
break;
}
waveStart = i+1;
@ -1575,7 +1564,7 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
//set start of wave as clock align
lastClkBit = firstFullWave;
if (g_debugMode==2) prnt("DEBUG PSK: firstFullWave: %u, waveLen: %u",firstFullWave,fullWaveLen);
if (g_debugMode==2) prnt("DEBUG: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit,(unsigned int) fc);
if (g_debugMode==2) prnt("DEBUG PSK: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit,(unsigned int) fc);
waveStart = 0;
dest[numBits++] = curPhase; //set first read bit
for (i = firstFullWave + fullWaveLen - 1; i < *size-3; i++){
@ -1606,6 +1595,9 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
} else if (i+1 > lastClkBit + *clock + tol + fc){
lastClkBit += *clock; //no phase shift but clock bit
dest[numBits++] = curPhase;
} else if (waveLenCnt < fc - 1) { //wave is smaller than field clock (shouldn't happen often)
errCnt2++;
if(errCnt2 > 101) return errCnt2;
}
avgWaveVal = 0;
waveStart = i+1;