proxmark3/common/lfdemod.c

//-----------------------------------------------------------------------------
// Copyright (C) 2014
//
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// Low frequency demod/decode commands   - by marshmellow, holiman, iceman and
//                                         many others who came before
//
// NOTES: 
// LF Demod functions are placed here to allow the flexability to use client or
// device side. Most BUT NOT ALL of these functions are currenlty safe for 
// device side use currently. (DetectST for example...)
//
// There are likely many improvements to the code that could be made, please
// make suggestions...
//
// we tried to include author comments so any questions could be directed to 
// the source.
//
// There are 4 main sections of code below:
//
// Utilities Section: 
//    for general utilities used by multiple other functions
//
// Clock / Bitrate Detection Section:
//    for clock detection functions for each modulation
//
// Modulation Demods &/or Decoding Section:
//    for main general modulation demodulating and encoding decoding code.
//
// Tag format detection section:
//    for detection of specific tag formats within demodulated data
//
// marshmellow
//-----------------------------------------------------------------------------

#include <string.h>  // for memset, memcmp and size_t
#include "lfdemod.h"
#include <stdint.h>  // for uint_32+
#include <stdbool.h> // for bool
#include "parity.h"  // for parity test

//**********************************************************************************************
//---------------------------------Utilities Section--------------------------------------------
//**********************************************************************************************
#define LOWEST_DEFAULT_CLOCK 32
#define FSK_PSK_THRESHOLD   123
//might not be high enough for noisy environments
#define NOICE_AMPLITUDE_THRESHOLD 10
//to allow debug print calls when used not on dev

//void dummy(char *fmt, ...){}
extern void Dbprintf(const char *fmt, ...);

#ifndef ON_DEVICE
#include "ui.h"
# include "cmdparser.h"
# include "cmddata.h"
# define prnt PrintAndLog
#else 
  uint8_t g_debugMode = 0;
# define prnt Dbprintf
#endif

signal_t signalprop = { 255, -255, 0, 0, true };
signal_t* getSignalProperties(void) {
	return &signalprop;
}

static void resetSignal(void) {
	signalprop.low = 255;
	signalprop.high = -255;
	signalprop.mean = 0;
	signalprop.amplitude = 0;
	signalprop.isnoise = true;
}
static void printSignal(void) {
	prnt("LF Signal properties:");
	prnt("  high..........%d", signalprop.high);
	prnt("  low...........%d", signalprop.low);
	prnt("  mean..........%d", signalprop.mean);
	prnt("  amplitude.....%d", signalprop.amplitude);
	prnt("  is Noise......%s", (signalprop.isnoise) ? "Yes" : "No");
	prnt("  THRESHOLD noice amplitude......%d" , NOICE_AMPLITUDE_THRESHOLD);
}

// Function to compute mean for a series
// rounded to integer..
uint32_t compute_mean_uint(uint8_t *in, size_t N) {
	uint32_t mean = 0;
	for (size_t i = 0; i < N; i++)
		mean += in[i];		

	return mean / N;
}
// Function to compute mean for a series
// rounded to integer..
int32_t compute_mean_int(int *in, size_t N) {
	int32_t mean = 0;
	for (size_t i = 0; i < N; i++)
		mean += in[i];
	
	return mean / (int)N;
}

//test samples are not just noise
// By measuring mean and look at amplitude of signal from HIGH / LOW,   we can detect noise
bool isNoise_int(int *bits, uint32_t size) {
	resetSignal();
	if ( bits == NULL || size < 100 ) return true;

	int32_t sum = 0;
	for ( size_t i = 0; i < size; i++) {
		if ( bits[i] < signalprop.low ) signalprop.low = bits[i];
		if ( bits[i] > signalprop.high ) signalprop.high = bits[i];
		sum += bits[i];		
	}

	// measure amplitude of signal
	signalprop.mean = sum / (int)size;
	signalprop.amplitude = ABS(signalprop.high - signalprop.mean);
	signalprop.isnoise = signalprop.amplitude < NOICE_AMPLITUDE_THRESHOLD;
	
	if (g_debugMode == 1) 
		printSignal();
	
	return signalprop.isnoise;
}
//test samples are not just noise
// By measuring mean and look at amplitude of signal from HIGH / LOW, 
// we can detect noise
bool isNoise(uint8_t *bits, uint32_t size) {
	resetSignal();
	if ( bits == NULL || size < 100 ) return true;
	
	uint32_t sum = 0;
	for ( uint32_t i = 0; i < size; i++) {
		if ( bits[i] < signalprop.low ) signalprop.low = bits[i];
		if ( bits[i] > signalprop.high ) signalprop.high = bits[i];
		sum += bits[i];		
	}

	// measure amplitude of signal
	signalprop.mean = sum / size;
	signalprop.amplitude = signalprop.high - signalprop.mean;
	signalprop.isnoise =  signalprop.amplitude < NOICE_AMPLITUDE_THRESHOLD;
	
	if (g_debugMode == 1) 
		printSignal();

	return signalprop.isnoise;
}

//by marshmellow
//get high and low values of a wave with passed in fuzz factor. also return noise test = 1 for passed or 0 for only noise
int getHiLo(uint8_t *bits, size_t size, int *high, int *low, uint8_t fuzzHi, uint8_t fuzzLo) {

	// just noise - no super good detection. good enough
	if (signalprop.isnoise) return -1; 
	
	// add fuzz.
	*high = ((signalprop.high - 128) * fuzzHi + 12800)/100;
	*low = ((signalprop.low - 128) * fuzzLo + 12800)/100;
	
	if (g_debugMode == 1) 
		prnt("getHiLo fuzzed: High %d | Low %d", *high, *low);
	return 1;
}

// by marshmellow
// pass bits to be tested in bits, length bits passed in bitLen, and parity type (even=0 | odd=1) in pType
// returns 1 if passed
bool parityTest(uint32_t bits, uint8_t bitLen, uint8_t pType) {
	return oddparity32(bits) ^ pType;
}

//by marshmellow
// takes a array of binary values, start position, length of bits per parity (includes parity bit - MAX 32),
//   Parity Type (1 for odd; 0 for even; 2 for Always 1's; 3 for Always 0's), and binary Length (length to run) 
size_t removeParity(uint8_t *bits, size_t startIdx, uint8_t pLen, uint8_t pType, size_t bLen) {
	uint32_t parityWd = 0;
	size_t bitCnt = 0;
	for (int word = 0; word < (bLen); word += pLen){
		for (int bit=0; bit < pLen; bit++){
			if (word+bit >= bLen) break;
			parityWd = (parityWd << 1) | bits[startIdx+word+bit];
			bits[bitCnt++] = (bits[startIdx+word+bit]);
		}
		if (word+pLen > bLen) break;

		bitCnt--; // overwrite parity with next data
		// if parity fails then return 0
		switch (pType) {
			case 3: if (bits[bitCnt]==1) {return 0;} break; //should be 0 spacer bit
			case 2: if (bits[bitCnt]==0) {return 0;} break; //should be 1 spacer bit
			default: if (parityTest(parityWd, pLen, pType) == 0) { return 0; } break; //test parity
		}
		parityWd = 0;
	}
	// if we got here then all the parities passed
	//return size
	return bitCnt;
}

// by marshmellow
// takes a array of binary values, length of bits per parity (includes parity bit),
//   Parity Type (1 for odd; 0 for even; 2 Always 1's; 3 Always 0's), and binary Length (length to run)
//   Make sure *dest is long enough to store original sourceLen + #_of_parities_to_be_added
size_t addParity(uint8_t *src, uint8_t *dest, uint8_t sourceLen, uint8_t pLen, uint8_t pType) {
	uint32_t parityWd = 0;
	size_t j = 0, bitCnt = 0;
	for (int word = 0; word < sourceLen; word += pLen-1) {
		for (int bit=0; bit < pLen-1; bit++){
			parityWd = (parityWd << 1) | src[word+bit];
			dest[j++] = (src[word+bit]);
		}
		// if parity fails then return 0
		switch (pType) {
			case 3: dest[j++]=0; break; // marker bit which should be a 0
			case 2: dest[j++]=1; break; // marker bit which should be a 1
			default: 
				dest[j++] = parityTest(parityWd, pLen-1, pType) ^ 1;
				break;
		}
		bitCnt += pLen;
		parityWd = 0;
	}
	// if we got here then all the parities passed
	//return ID start index and size
	return bitCnt;
}

// array must be size dividable with 8
uint8_t bits_to_array(const uint8_t *bits, size_t size, uint8_t *dest) {
	if ( (size == 0) || (size % 8) != 0) return 0;
	
	for(uint32_t i = 0; i < (size / 8); i++)
		dest[i] = bytebits_to_byte((uint8_t *) bits + (i * 8), 8);

	return 0;
}

uint32_t bytebits_to_byte(uint8_t *src, size_t numbits) {
	uint32_t num = 0;
	for(int i = 0 ; i < numbits ; i++) {
		num = (num << 1) | (*src);
		src++;
	}
	return num;
}

//least significant bit first
uint32_t bytebits_to_byteLSBF(uint8_t *src, size_t numbits) {
	uint32_t num = 0;
	for(int i = 0 ; i < numbits ; i++) {
		num = (num << 1) | *(src + (numbits-(i+1)));
	}
	return num;
}

//by marshmellow
//search for given preamble in given BitStream and return success = TRUE or fail = FALSE and startIndex and length
bool preambleSearch(uint8_t *bits, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx){
	return preambleSearchEx(bits, preamble, pLen, size, startIdx, false);
}
//by marshmellow
// search for given preamble in given BitStream and return success=1 or fail=0 and startIndex (where it was found) and length if not fineone 
// fineone does not look for a repeating preamble for em4x05/4x69 sends preamble once, so look for it once in the first pLen bits
//(iceman) FINDONE,  only finds start index. NOT SIZE!.  I see Em410xDecode (lfdemod.c) uses SIZE to determine success
bool preambleSearchEx(uint8_t *bits, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx, bool findone)
{
	// Sanity check.  If preamble length is bigger than bits length.
	if ( *size <= pLen ) return false;
	
	uint8_t foundCnt = 0;
	for (size_t idx = 0; idx < *size - pLen; idx++) {
		if (memcmp(bits+idx, preamble, pLen) == 0){
			//first index found
			foundCnt++;
			if (foundCnt == 1){
				if (g_debugMode) prnt("DEBUG: (preambleSearchEx) preamble found at %i", idx);
				*startIdx = idx;
				if (findone) return true;
			}
			if (foundCnt == 2){
				if (g_debugMode) prnt("DEBUG: (preambleSearchEx) preamble 2 found at %i", idx);
				*size = idx - *startIdx;
				return true;
			}
		}
	}
	return (foundCnt > 0);
}

// find start of modulating data (for fsk and psk) in case of beginning noise or slow chip startup.
size_t findModStart(uint8_t *src, size_t size, uint8_t expWaveSize) {
	size_t i = 0;
	size_t waveSizeCnt = 0;
	uint8_t thresholdCnt = 0;
	bool isAboveThreshold = src[i++] >= FSK_PSK_THRESHOLD;
	for (; i < size-20; i++ ) {
		if(src[i] < FSK_PSK_THRESHOLD && isAboveThreshold) {
			thresholdCnt++;
			if (thresholdCnt > 2 && waveSizeCnt < expWaveSize+1) break;			
			isAboveThreshold = false;
			waveSizeCnt = 0;
		} else if (src[i] >= FSK_PSK_THRESHOLD && !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;
}

int getClosestClock(int testclk) {
	uint8_t clocks[] = {8,16,32,40,50,64,128};

	for (uint8_t i = 0; i < 7; i++)
		if ( testclk >= clocks[i] - (clocks[i]/8) && testclk <= clocks[i]+1 )
			return clocks[i];

	return 0;
}

void getNextLow(uint8_t *samples, size_t size, int low, size_t *i) {
	while ((samples[*i] > low) && (*i < size))
		*i += 1;
}

void getNextHigh(uint8_t *samples, size_t size, int high, size_t *i) {
	while ((samples[*i] < high) && (*i < size))
		*i += 1;
}

// load wave counters
bool loadWaveCounters(uint8_t *samples, size_t size, int lowToLowWaveLen[], int highToLowWaveLen[], int *waveCnt, int *skip, int *minClk, int *high, int *low) {
	size_t i=0, firstLow, firstHigh;
	size_t testsize = (size < 512) ? size : 512;

	if ( getHiLo(samples, testsize, high, low, 80, 80) == -1 ) {
		if (g_debugMode==2) prnt("DEBUG STT: just noise detected - quitting");
		return false; //just noise
	}

	// get to first full low to prime loop and skip incomplete first pulse
	getNextHigh(samples, size, *high, &i);
	getNextLow(samples, size, *low, &i);
	*skip = i;

	// populate tmpbuff buffer with pulse lengths
	while (i < size) {
		// measure from low to low
		firstLow = i;
		//find first high point for this wave
		getNextHigh(samples, size, *high, &i);
		firstHigh = i;

		getNextLow(samples, size, *low, &i);

		if (*waveCnt >= (size/LOWEST_DEFAULT_CLOCK))
			break;

		highToLowWaveLen[*waveCnt] = i - firstHigh; //first high to first low
		lowToLowWaveLen[*waveCnt] = i - firstLow;
		*waveCnt += 1;
		if (i-firstLow < *minClk && i < size) {
			*minClk = i - firstLow;
		}
	}
	return true;
}

size_t pskFindFirstPhaseShift(uint8_t *samples, size_t size, uint8_t *curPhase, size_t waveStart, uint16_t fc, uint16_t *fullWaveLen) {
	uint16_t loopCnt = (size+3 < 4096) ? size : 4096;  //don't need to loop through entire array...

	uint16_t avgWaveVal=0, lastAvgWaveVal=0;
	size_t i = waveStart, waveEnd, waveLenCnt, firstFullWave;
	for (; i<loopCnt; i++) {
		// find peak // was "samples[i] + fc" but why?  must have been used to weed out some wave error... removed..
		if (samples[i] < samples[i+1] && samples[i+1] >= samples[i+2]){
			waveEnd = i+1;
			if (g_debugMode == 2) prnt("DEBUG PSK: waveEnd: %u, waveStart: %u", waveEnd, waveStart);
			waveLenCnt = waveEnd-waveStart;
			if (waveLenCnt > fc && waveStart > fc && !(waveLenCnt > fc+8)){ //not first peak and is a large wave but not out of whack
				lastAvgWaveVal = avgWaveVal/(waveLenCnt);
				firstFullWave = waveStart;
				*fullWaveLen = waveLenCnt;
				//if average wave value is > graph 0 then it is an up wave or a 1 (could cause inverting)
				if (lastAvgWaveVal > FSK_PSK_THRESHOLD) *curPhase ^= 1;
				return firstFullWave;
			}
			waveStart = i+1;
			avgWaveVal = 0;
		}
		avgWaveVal += samples[i+2];
	}
	return 0;
}

//by marshmellow
//amplify based on ask edge detection  -  not accurate enough to use all the time
void askAmp(uint8_t *bits, size_t size) {
	uint8_t last = 128;
	for(size_t i = 1; i < size; ++i){
		if ( bits[i] - bits[i-1] >= 30) //large jump up
			last = 255;
		else if ( bits[i-1] - bits[i] >= 20) //large jump down
			last = 0;
		
		bits[i] = last;
	}
}

// iceman, simplify this
uint32_t manchesterEncode2Bytes(uint16_t datain) {
	uint32_t output = 0;
	uint8_t curBit = 0;
	for (uint8_t i = 0; i < 16; i++) {
		curBit = (datain >> (15-i) & 1);
		output |= ( 1 << ( ( (15-i) * 2 ) + curBit));
	}
	return output;
}

//by marshmellow
//encode binary data into binary manchester 
//NOTE: bitstream must have triple the size of "size" available in memory to do the swap
int ManchesterEncode(uint8_t *bits, size_t size) {
	//allow up to 4096b out (means bits must be at least 2048+4096 to handle the swap)
	size = (size > 2048) ? 2048 : size;
	size_t modIdx = size;
	size_t i;
	for (size_t idx=0; idx < size; idx++){
		bits[idx+modIdx++] = bits[idx];
		bits[idx+modIdx++] = bits[idx]^1;
	}
	for (i=0; i < (size*2); i++){
		bits[i] = bits[i+size];
	}
	return i;
}

// by marshmellow
// to detect a wave that has heavily clipped (clean) samples
uint8_t DetectCleanAskWave(uint8_t *dest, size_t size, uint8_t high, uint8_t low) {
	bool allArePeaks = true;
	uint16_t cntPeaks = 0;
	size_t loopEnd = 512 + 160;
	
	// sanity check
	if (loopEnd > size) loopEnd = size;
	
	for (size_t i = 160; i < loopEnd; i++){
		
		if (dest[i] > low && dest[i] < high) 
			allArePeaks = false;
		else
			cntPeaks++;
	}
	if (!allArePeaks){
		if (cntPeaks > 300) return true;
	}
	return allArePeaks;
}


//**********************************************************************************************
//-------------------Clock / Bitrate Detection Section------------------------------------------
//**********************************************************************************************


// by marshmellow
// to help detect clocks on heavily clipped samples
// based on count of low to low
int DetectStrongAskClock(uint8_t *dest, size_t size, int high, int low, int *clock) {
	size_t startwave;
	size_t i = 100;
	size_t minClk = 512;
	int shortestWaveIdx = 0;

	// get to first full low to prime loop and skip incomplete first pulse
	getNextHigh(dest, size, high, &i);
	getNextLow(dest, size, low, &i);

	// loop through all samples
	while (i < size) {
		// measure from low to low
		startwave= i;

		getNextHigh(dest, size, high, &i);
		getNextLow(dest, size, low, &i);
		
		//get minimum measured distance
		if (i-startwave < minClk && i < size) {
			minClk = i - startwave;
			shortestWaveIdx = startwave;
		}
	}
	
	// set clock
	if (g_debugMode==2) prnt("DEBUG ASK: DetectStrongAskClock smallest wave: %d", minClk);
	*clock = getClosestClock(minClk);
	if (*clock == 0) 
		return 0;
	
	return shortestWaveIdx;
}

// by marshmellow
// not perfect especially with lower clocks or VERY good antennas (heavy wave clipping)
// maybe somehow adjust peak trimming value based on samples to fix?
// return start index of best starting position for that clock and return clock (by reference)
int DetectASKClock(uint8_t *dest, size_t size, int *clock, int maxErr) {
	size_t i = 1;
	uint16_t clk[] = {255,8,16,32,40,50,64,100,128,255};
	uint16_t clkEnd = 9;
	uint16_t loopCnt = 1500;  //don't need to loop through entire array...  (cotag has clock of 384)
	if (size <= loopCnt + 60) return -1; //not enough samples
	size -= 60; //sometimes there is a strange end wave - filter out this....
	//if we already have a valid clock
	uint8_t clockFnd = 0;
	for (; i < clkEnd; ++i)
		if (clk[i] == *clock) clockFnd = i;
		//clock found but continue to find best startpos

	//get high and low peak
	int peak, low;
	if (getHiLo(dest, loopCnt, &peak, &low, 75, 75) < 1) return -1;
	
	//test for large clean peaks
	if (!clockFnd){
		if (DetectCleanAskWave(dest, size, peak, low)==1){
			int ans = DetectStrongAskClock(dest, size, peak, low, clock);
			if (g_debugMode==2) prnt("DEBUG ASK: detectaskclk Clean Ask Wave Detected: clk %i, ShortestWave: %i", *clock ,ans);
			if (ans > 0){
				return ans; //return shortest wave start position
			}
		}
	}
	// test clock if given as cmd parameter
	if ( *clock > 0 )
		clk[0] = *clock;
	
	uint16_t ii;
	uint8_t clkCnt, tol = 0;
	uint16_t bestErr[]={1000,1000,1000,1000,1000,1000,1000,1000,1000};
	uint8_t bestStart[]={0,0,0,0,0,0,0,0,0};
	size_t errCnt = 0;
	size_t arrLoc, loopEnd;

	if (clockFnd > 0) {
		clkCnt = clockFnd;
		clkEnd = clockFnd+1;
	} else {
		clkCnt = 1;
	}

	//test each valid clock from smallest to greatest to see which lines up
	for (; clkCnt < clkEnd; clkCnt++) {
		if (clk[clkCnt] <= 32) {
			tol=1;
		} else {
			tol=0;
		}
		//if no errors allowed - keep start within the first clock
		if (!maxErr && size > clk[clkCnt]*2 + tol && clk[clkCnt] < 128) 
			loopCnt = clk[clkCnt] * 2;

		bestErr[clkCnt] = 1000;

		//try lining up the peaks by moving starting point (try first few clocks)
		for (ii=0; ii < loopCnt; ii++){
			if (dest[ii] < peak && dest[ii] > low) continue;

			errCnt = 0;
			// now that we have the first one lined up test rest of wave array
			loopEnd = ((size-ii-tol) / clk[clkCnt]) - 1;
			for (i=0; i < loopEnd; ++i){
				arrLoc = ii + (i * clk[clkCnt]);
				if (dest[arrLoc] >= peak || dest[arrLoc] <= low){
				}else if (dest[arrLoc-tol] >= peak || dest[arrLoc-tol] <= low){
				}else if (dest[arrLoc+tol] >= peak || dest[arrLoc+tol] <= low){
				}else{  //error no peak detected
					errCnt++;
				}
			}
			//if we found no errors then we can stop here and a low clock (common clocks)
			//  this is correct one - return this clock
			if (g_debugMode == 2) prnt("DEBUG ASK: clk %d, err %d, startpos %d, endpos %d", clk[clkCnt], errCnt, ii, i);
			if (errCnt==0 && clkCnt<7) { 
				if (!clockFnd) *clock = clk[clkCnt];
				return ii;
			}
			//if we found errors see if it is lowest so far and save it as best run
			if (errCnt < bestErr[clkCnt]) {
				bestErr[clkCnt] = errCnt;
				bestStart[clkCnt] = ii;
			}
		}
	}
	uint8_t k;
	uint8_t best = 0;
	for (k=1; k < clkEnd; ++k){
		if (bestErr[k] < bestErr[best]){
			if (bestErr[k] == 0) bestErr[k]=1;
			// current best bit to error ratio     vs  new bit to error ratio
			if ( (size/clk[best])/bestErr[best] < (size/clk[k])/bestErr[k] ){
				best = k;
			}
		}
		if (g_debugMode == 2) prnt("DEBUG ASK: clk %d, # Errors %d, Current Best Clk %d, bestStart %d", clk[k], bestErr[k], clk[best], bestStart[best]);
	}
	if (!clockFnd) *clock = clk[best];
	
	return bestStart[best];
}

int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low, bool *strong) {
	//find shortest transition from high to low
	*strong = false;
	size_t i = 0;
	size_t transition1 = 0;
	int lowestTransition = 255;
	bool lastWasHigh = false;
	size_t transitionSampleCount = 0;
	//find first valid beginning of a high or low wave
	while ((dest[i] >= peak || dest[i] <= low) && (i < size))
		++i;
	while ((dest[i] < peak && dest[i] > low) && (i < size))
		++i;

	lastWasHigh = (dest[i] >= peak);

	if (i == size)
		return 0;

	transition1 = i;

	for (;i < size; i++) {
		if ((dest[i] >= peak && !lastWasHigh) || (dest[i] <= low && lastWasHigh)) {
			lastWasHigh = (dest[i] >= peak);
			if (i-transition1 < lowestTransition) 
				lowestTransition = i-transition1;
			transition1 = i;
		} else if (dest[i] < peak && dest[i] > low) {
			transitionSampleCount++;
		}
	}
	if (lowestTransition == 255) 
		lowestTransition = 0;
	
	if (g_debugMode==2) prnt("DEBUG NRZ: detectstrongNRZclk smallest wave: %d", lowestTransition);
	// if less than 10% of the samples were not peaks (or 90% were peaks) then we have a strong wave
	if (transitionSampleCount / size < 10) {
		*strong = true;
		lowestTransition = getClosestClock(lowestTransition);
	}
	return lowestTransition;
}

//by marshmellow
//detect nrz clock by reading #peaks vs no peaks(or errors)
int DetectNRZClock(uint8_t *dest, size_t size, int clock, size_t *clockStartIdx) {
	size_t i = 0;
	uint8_t clk[] = {8,16,32,40,50,64,100,128,255};
	size_t loopCnt = 4096;  //don't need to loop through entire array...

	//if we already have a valid clock quit
	for (; i < 8; ++i)
		if (clk[i] == clock) return clock;
	
	if (size < 20) return 0;
	// size must be larger than 20 here
	if (size < loopCnt) loopCnt = size-20;

	//get high and low peak
	int peak, low;
	if (getHiLo(dest, loopCnt, &peak, &low, 90, 90) < 1) return 0;

	bool strong = false;
	int lowestTransition = DetectStrongNRZClk(dest, size-20, peak, low, &strong);
	if (strong) return lowestTransition;
	size_t ii;
	uint8_t clkCnt;
	uint8_t tol = 0;
	uint16_t smplCnt = 0;
	int16_t peakcnt = 0;
	int16_t peaksdet[] = {0,0,0,0,0,0,0,0};
	uint16_t minPeak = 255;
	bool firstpeak = true;
	//test for large clipped waves - ignore first peak
	for (i=0; i<loopCnt; i++){
		if (dest[i] >= peak || dest[i] <= low){
			if (firstpeak) continue;
			smplCnt++;
		} else {
			firstpeak = false;
			if (smplCnt > 0) {
				if (minPeak > smplCnt && smplCnt > 7) minPeak = smplCnt;
				peakcnt++;
				if (g_debugMode == 2) prnt("DEBUG NRZ: minPeak: %d, smplCnt: %d, peakcnt: %d",minPeak,smplCnt,peakcnt);
				smplCnt = 0;
			}
		}
	}
	if (minPeak < 8) return 0;
	
	bool errBitHigh = 0, bitHigh = 0, lastPeakHigh = 0;
	uint8_t ignoreCnt = 0, ignoreWindow = 4;
	int lastBit = 0; 
	size_t bestStart[] = {0,0,0,0,0,0,0,0,0};
	peakcnt = 0;
	//test each valid clock from smallest to greatest to see which lines up
	for (clkCnt=0; clkCnt < 8; ++clkCnt){
		//ignore clocks smaller than smallest peak
		if (clk[clkCnt] < minPeak - (clk[clkCnt]/4)) continue;
		//try lining up the peaks by moving starting point (try first 256)
		for (ii=20; ii < loopCnt; ++ii){
			if ((dest[ii] >= peak) || (dest[ii] <= low)){
				peakcnt=0;
				bitHigh = false;
				ignoreCnt = 0;
				lastBit = ii-clk[clkCnt]; 
				//loop through to see if this start location works
				for (i = ii; i < size-20; ++i) {
					//if we are at a clock bit
					if ((i >= lastBit + clk[clkCnt] - tol) && (i <= lastBit + clk[clkCnt] + tol)) {
						//test high/low
						if (dest[i] >= peak || dest[i] <= low) {
							//if same peak don't count it
							if ((dest[i] >= peak && !lastPeakHigh) || (dest[i] <= low && lastPeakHigh)) {
								peakcnt++;
							}
							lastPeakHigh = (dest[i] >= peak);
							bitHigh = true;
							errBitHigh = false;
							ignoreCnt = ignoreWindow;
							lastBit += clk[clkCnt];
						} else if (i == lastBit + clk[clkCnt] + tol) {
							lastBit += clk[clkCnt];
						}
					//else if not a clock bit and no peaks
					} else if (dest[i] < peak && dest[i] > low){
						if (ignoreCnt == 0){
							bitHigh = false;
							if (errBitHigh == true) 
								peakcnt--;
							errBitHigh = false;
						} else {
							ignoreCnt--;
						}
						// else if not a clock bit but we have a peak
					} else if ((dest[i] >= peak || dest[i] <= low) && (!bitHigh)) {
						//error bar found no clock...
						errBitHigh = true;
					}
				}
				if (peakcnt > peaksdet[clkCnt]) {
					bestStart[clkCnt] = ii;
					peaksdet[clkCnt] = peakcnt;
				}
			}
		}
	}

	uint8_t best = 0;
	for (int m = 7; m > 0; m--){
		if ((peaksdet[m] >= (peaksdet[best]-1)) && (peaksdet[m] <= peaksdet[best]+1) && lowestTransition) {
			if (clk[m] > (lowestTransition - (clk[m]/8)) && clk[m] < (lowestTransition + (clk[m]/8))) {
				best = m;
			}
		} else if (peaksdet[m] > peaksdet[best]){
			best = m;
		}
		if (g_debugMode==2) prnt("DEBUG NRZ: Clk: %d, peaks: %d, minPeak: %d, bestClk: %d, lowestTrs: %d", clk[m], peaksdet[m], minPeak, clk[best], lowestTransition);
	}
	*clockStartIdx	= bestStart[best];
	return clk[best];
}

//by marshmellow
//countFC is to detect the field clock lengths.
//counts and returns the 2 most common wave lengths
//mainly used for FSK field clock detection
uint16_t countFC(uint8_t *bits, size_t size, uint8_t fskAdj) {
	uint8_t fcLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
	uint16_t fcCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
	uint8_t fcLensFnd = 0;
	uint8_t lastFCcnt = 0;
	uint8_t fcCounter = 0;
	size_t i;
	if (size < 180) return 0;

	// prime i to first up transition
	for (i = 160; i < size-20; i++)
		if (bits[i] > bits[i-1] && bits[i] >= bits[i+1])
			break;

	for (; i < size-20; i++){
		if (bits[i] > bits[i-1] && bits[i] >= bits[i+1]){
			// new up transition
			fcCounter++;
			if (fskAdj){
				//if we had 5 and now have 9 then go back to 8 (for when we get a fc 9 instead of an 8)
				if (lastFCcnt==5 && fcCounter==9) fcCounter--;
				//if fc=9 or 4 add one (for when we get a fc 9 instead of 10 or a 4 instead of a 5)
				if ((fcCounter==9) || fcCounter==4) fcCounter++;
			// save last field clock count  (fc/xx)
			lastFCcnt = fcCounter;
			}
			// find which fcLens to save it to:
			for (int ii=0; ii<15; ii++){
				if (fcLens[ii]==fcCounter){
					fcCnts[ii]++;
					fcCounter=0;
					break;
				}
			}
			if (fcCounter>0 && fcLensFnd<15){
				//add new fc length 
				fcCnts[fcLensFnd]++;
				fcLens[fcLensFnd++] = fcCounter;
			}
			fcCounter=0;
		} else {
			// count sample
			fcCounter++;
		}
	}
	
	uint8_t best1=14, best2=14, best3=14;
	uint16_t maxCnt1=0;
	// go through fclens and find which ones are bigest 2  
	for (i=0; i<15; i++){
		// get the 3 best FC values
		if (fcCnts[i]>maxCnt1) {
			best3=best2;
			best2=best1;
			maxCnt1=fcCnts[i];
			best1=i;
		} else if(fcCnts[i]>fcCnts[best2]){
			best3=best2;
			best2=i;
		} else if(fcCnts[i]>fcCnts[best3]){
			best3=i;
		}
		if (g_debugMode==2) prnt("DEBUG countfc: FC %u, Cnt %u, best fc: %u, best2 fc: %u",fcLens[i],fcCnts[i],fcLens[best1],fcLens[best2]);
		if (fcLens[i]==0) break;
	}
	if (fcLens[best1]==0) return 0;
	uint8_t fcH=0, fcL=0;
	if (fcLens[best1]>fcLens[best2]){
		fcH=fcLens[best1];
		fcL=fcLens[best2];
	} else{
		fcH=fcLens[best2];
		fcL=fcLens[best1];
	}
	if ((size-180)/fcH/3 > fcCnts[best1]+fcCnts[best2]) {
		if (g_debugMode==2) prnt("DEBUG countfc: fc is too large: %u > %u. Not psk or fsk",(size-180)/fcH/3,fcCnts[best1]+fcCnts[best2]);
		return 0; //lots of waves not psk or fsk
	}
	// TODO: take top 3 answers and compare to known Field clocks to get top 2

	uint16_t fcs = (((uint16_t)fcH)<<8) | fcL;
	if (fskAdj) return fcs;	
	return (uint16_t)fcLens[best2] << 8 | fcLens[best1];
}

//by marshmellow
//detect psk clock by reading each phase shift
// a phase shift is determined by measuring the sample length of each wave
int DetectPSKClock(uint8_t *dest, size_t size, int clock, size_t *firstPhaseShift, uint8_t *curPhase, uint8_t *fc) {
	uint8_t clk[] = {255,16,32,40,50,64,100,128,255}; //255 is not a valid clock
	uint16_t loopCnt = 4096;  //don't need to loop through entire array...

	//if we already have a valid clock quit
	size_t i = 1;
	for (; i < 8; ++i)
		if (clk[i] == clock) return clock;

	if (size < 160+20) return 0;
	// size must be larger than 20 here, and 160 later on.
	if (size < loopCnt) loopCnt = size-20;	

	uint16_t fcs = countFC(dest, size, 0);
	
	*fc = fcs & 0xFF;
	
	if (g_debugMode==2) prnt("DEBUG PSK: FC: %d, FC2: %d",*fc, fcs>>8);
	
	if ((fcs >> 8) == 10 && *fc == 8) return 0;
	
	if (*fc != 2 && *fc != 4 && *fc != 8) return 0;


	size_t waveStart=0, waveEnd=0, firstFullWave=0, lastClkBit=0;

	uint8_t clkCnt, tol=1;
	uint16_t peakcnt=0, errCnt=0, waveLenCnt=0, fullWaveLen=0;
	uint16_t bestErr[] = {1000,1000,1000,1000,1000,1000,1000,1000,1000};
	uint16_t peaksdet[] = {0,0,0,0,0,0,0,0,0};

	//find start of modulating data in trace 
	i = findModStart(dest, size, *fc);

	firstFullWave = pskFindFirstPhaseShift(dest, size, curPhase, i, *fc, &fullWaveLen);
	if (firstFullWave == 0) {
		// no phase shift detected - could be all 1's or 0's - doesn't matter where we start
		// so skip a little to ensure we are past any Start Signal
		firstFullWave = 160;
		fullWaveLen = 0;
	}

	*firstPhaseShift = firstFullWave;
	if (g_debugMode == 2) prnt("DEBUG PSK: firstFullWave: %d, waveLen: %d",firstFullWave,fullWaveLen);
	
	//test each valid clock from greatest to smallest to see which lines up
	for (clkCnt=7; clkCnt >= 1 ; clkCnt--){
		tol = *fc/2;
		lastClkBit = firstFullWave; //set end of wave as clock align
		waveStart = 0;
		errCnt = 0;
		peakcnt = 0;
		if (g_debugMode == 2) prnt("DEBUG PSK: clk: %d, lastClkBit: %d", clk[clkCnt], lastClkBit);

		for (i = firstFullWave+fullWaveLen-1; i < loopCnt-2; i++){
			//top edge of wave = start of new wave 
			if (dest[i] < dest[i+1] && dest[i+1] >= dest[i+2]){
				if (waveStart == 0) {
					waveStart = i+1;
					waveLenCnt = 0;
				} else { //waveEnd
					waveEnd = i+1;
					waveLenCnt = waveEnd-waveStart;
					if (waveLenCnt > *fc){ 
						//if this wave is a phase shift
						if (g_debugMode == 2) prnt("DEBUG PSK: phase shift at: %d, len: %d, nextClk: %d, i: %d, fc: %d", waveStart, waveLenCnt, lastClkBit + clk[clkCnt] - tol, i+1, *fc);
						if (i+1 >= lastClkBit + clk[clkCnt] - tol){ //should be a clock bit
							peakcnt++;
							lastClkBit += clk[clkCnt];
						} else if (i < lastClkBit+8){
							//noise after a phase shift - ignore
						} else { //phase shift before supposed to based on clock
							errCnt++;
						}
					} else if (i+1 > lastClkBit + clk[clkCnt] + tol + *fc){
						lastClkBit+=clk[clkCnt]; //no phase shift but clock bit
					}
					waveStart = i+1;
				}
			}
		}
		if (errCnt == 0) return clk[clkCnt];
		if (errCnt <= bestErr[clkCnt]) bestErr[clkCnt] = errCnt;
		if (peakcnt > peaksdet[clkCnt]) peaksdet[clkCnt] = peakcnt;
	} 
	//all tested with errors 
	//return the highest clk with the most peaks found
	uint8_t best = 7;
	for (i=7; i >= 1; i--){
		if (peaksdet[i] > peaksdet[best])
			best = i;

		if (g_debugMode == 2) prnt("DEBUG PSK: Clk: %d, peaks: %d, errs: %d, bestClk: %d",clk[i],peaksdet[i],bestErr[i],clk[best]);
	}
	return clk[best];
}

//by marshmellow
//detects the bit clock for FSK given the high and low Field Clocks
uint8_t detectFSKClk(uint8_t *bits, size_t size, uint8_t fcHigh, uint8_t fcLow, int *firstClockEdge) {

	if (size == 0) 
		return 0;
	
	uint8_t clk[] = {8,16,32,40,50,64,100,128,0};
	uint16_t rfLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
	uint8_t rfCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
	uint8_t rfLensFnd = 0;
	uint8_t lastFCcnt = 0;
	uint16_t fcCounter = 0;
	uint16_t rfCounter = 0;
	uint8_t firstBitFnd = 0;
	size_t i;
	uint8_t fcTol = ((fcHigh*100 - fcLow*100)/2 + 50)/100; //(uint8_t)(0.5+(float)(fcHigh-fcLow)/2);

	// prime i to first peak / up transition
	for (i = 160; i < size-20; i++)
		if (bits[i] > bits[i-1] && bits[i] >= bits[i+1])
			break;

	for (; i < size-20; i++){
		fcCounter++;
		rfCounter++;

		if (bits[i] <= bits[i-1] || bits[i] < bits[i+1]) 
			continue;		
		// else new peak 
		// if we got less than the small fc + tolerance then set it to the small fc
		// if it is inbetween set it to the last counter
		if (fcCounter < fcHigh && fcCounter > fcLow)
			fcCounter = lastFCcnt;
		else if (fcCounter < fcLow+fcTol) 
			fcCounter = fcLow;
		else //set it to the large fc
			fcCounter = fcHigh;

		//look for bit clock  (rf/xx)
		if ((fcCounter < lastFCcnt || fcCounter > lastFCcnt)){
			//not the same size as the last wave - start of new bit sequence
			if (firstBitFnd > 1){ //skip first wave change - probably not a complete bit
				for (int ii=0; ii<15; ii++){
					if (rfLens[ii] >= (rfCounter-4) && rfLens[ii] <= (rfCounter+4)){
						rfCnts[ii]++;
						rfCounter = 0;
						break;
					}
				}
				if (rfCounter > 0 && rfLensFnd < 15){
					//prnt("DEBUG: rfCntr %d, fcCntr %d",rfCounter,fcCounter);
					rfCnts[rfLensFnd]++;
					rfLens[rfLensFnd++] = rfCounter;
				}
			} else {
				*firstClockEdge = i;
				firstBitFnd++;
			}
			rfCounter = 0;
			lastFCcnt = fcCounter;
		}
		fcCounter = 0;
	}
	uint8_t rfHighest=15, rfHighest2=15, rfHighest3=15;

	for (i=0; i<15; i++){
		//get highest 2 RF values  (might need to get more values to compare or compare all?)
		if (rfCnts[i] > rfCnts[rfHighest]){
			rfHighest3 = rfHighest2;
			rfHighest2 = rfHighest;
			rfHighest = i;
		} else if(rfCnts[i] > rfCnts[rfHighest2]){
			rfHighest3 = rfHighest2;
			rfHighest2 = i;
		} else if(rfCnts[i] > rfCnts[rfHighest3]){
			rfHighest3 = i;
		}
		if (g_debugMode==2) 
			prnt("DEBUG FSK: RF %d, cnts %d", rfLens[i], rfCnts[i]);
	}  
	// set allowed clock remainder tolerance to be 1 large field clock length+1 
	//   we could have mistakenly made a 9 a 10 instead of an 8 or visa versa so rfLens could be 1 FC off  
	uint8_t tol1 = fcHigh+1; 
	
	if (g_debugMode==2) 
		prnt("DEBUG FSK: most counted rf values: 1 %d, 2 %d, 3 %d", rfLens[rfHighest], rfLens[rfHighest2], rfLens[rfHighest3]);

	// loop to find the highest clock that has a remainder less than the tolerance
	//   compare samples counted divided by
	// test 128 down to 32 (shouldn't be possible to have fc/10 & fc/8 and rf/16 or less)
	int ii=7;
	for (; ii>=2; ii--){
		if (rfLens[rfHighest] % clk[ii] < tol1 || rfLens[rfHighest] % clk[ii] > clk[ii]-tol1){
			if (rfLens[rfHighest2] % clk[ii] < tol1 || rfLens[rfHighest2] % clk[ii] > clk[ii]-tol1){
				if (rfLens[rfHighest3] % clk[ii] < tol1 || rfLens[rfHighest3] % clk[ii] > clk[ii]-tol1){
					if (g_debugMode==2) 
						prnt("DEBUG FSK: clk %d divides into the 3 most rf values within tolerance",clk[ii]);
					break;
				}
			}
		}
	}

	if (ii < 2) return 0; // oops we went too far

	return clk[ii];
}


//**********************************************************************************************
//--------------------Modulation Demods &/or Decoding Section-----------------------------------
//**********************************************************************************************


// look for Sequence Terminator - should be pulses of clk*(1 or 2), clk*2, clk*(1.5 or 2), by idx we mean graph position index...
bool findST(int *stStopLoc, int *stStartIdx, int lowToLowWaveLen[], int highToLowWaveLen[], int clk, int tol, int buffSize, size_t *i) {
	if (buffSize < *i+4) return false;

	for (; *i < buffSize - 4; *i+=1) {
		*stStartIdx += lowToLowWaveLen[*i]; //caution part of this wave may be data and part may be ST....  to be accounted for in main function for now...
		if (lowToLowWaveLen[*i] >= clk*1-tol && lowToLowWaveLen[*i] <= (clk*2)+tol && highToLowWaveLen[*i] < clk+tol) {           //1 to 2 clocks depending on 2 bits prior
			if (lowToLowWaveLen[*i+1] >= clk*2-tol && lowToLowWaveLen[*i+1] <= clk*2+tol && highToLowWaveLen[*i+1] > clk*3/2-tol) {       //2 clocks and wave size is 1 1/2
				if (lowToLowWaveLen[*i+2] >= (clk*3)/2-tol && lowToLowWaveLen[*i+2] <= clk*2+tol && highToLowWaveLen[*i+2] > clk-tol) { //1 1/2 to 2 clocks and at least one full clock wave
					if (lowToLowWaveLen[*i+3] >= clk*1-tol && lowToLowWaveLen[*i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
						*stStopLoc = *i + 3;
						return true;
					}
				}
			}
		}
	}
	return false;
}
//by marshmellow
//attempt to identify a Sequence Terminator in ASK modulated raw wave
bool DetectST(uint8_t *buffer, size_t *size, int *foundclock, size_t *ststart, size_t *stend) {
	size_t bufsize = *size;
	//need to loop through all samples and identify our clock, look for the ST pattern
	int clk = 0; 
	int tol = 0;
	int j=0, high, low, skip=0, start=0, end=0, minClk=255;
	size_t i = 0;
	//probably should malloc... || test if memory is available ... handle device side? memory danger!!! [marshmellow]
	int tmpbuff[bufsize / LOWEST_DEFAULT_CLOCK]; // low to low wave count //guess rf/32 clock, if click is smaller we will only have room for a fraction of the samples captured
	int waveLen[bufsize / LOWEST_DEFAULT_CLOCK]; // high to low wave count //if clock is larger then we waste memory in array size that is not needed...
	//size_t testsize = (bufsize < 512) ? bufsize : 512;
	int phaseoff = 0;
	high = low = 128;
	memset(tmpbuff, 0, sizeof(tmpbuff));
	memset(waveLen, 0, sizeof(waveLen));

	if (!loadWaveCounters(buffer, bufsize, tmpbuff, waveLen, &j, &skip, &minClk, &high, &low)) return false;
	// set clock  - might be able to get this externally and remove this work...
	clk = getClosestClock(minClk);
		// clock not found - ERROR
		if (!clk) {
			if (g_debugMode==2) prnt("DEBUG STT: clock not found - quitting");
			return false;
		}
	*foundclock = clk;

	tol = clk/8;
	if (!findST(&start, &skip, tmpbuff, waveLen, clk, tol, j, &i)) {
	// first ST not found - ERROR
		if (g_debugMode==2) prnt("DEBUG STT: first STT not found - quitting");
		return false;
	} else {
		if (g_debugMode==2) prnt("DEBUG STT: first STT found at wave: %i, skip: %i, j=%i", start, skip, j);
	}
	if (waveLen[i+2] > clk*1+tol)
		phaseoff = 0;
	else
		phaseoff = clk/2;
	
	// skip over the remainder of ST
	skip += clk*7/2; //3.5 clocks from tmpbuff[i] = end of st - also aligns for ending point

	// now do it again to find the end
	int dummy1 = 0;
	end = skip;
	i += 3;
	if (!findST(&dummy1, &end, tmpbuff, waveLen, clk, tol, j, &i)) {
	//didn't find second ST - ERROR
		if (g_debugMode==2) prnt("DEBUG STT: second STT not found - quitting");
		return false;
	}
	end -= phaseoff;
	if (g_debugMode==2) prnt("DEBUG STT: start of data: %d end of data: %d, datalen: %d, clk: %d, bits: %d, phaseoff: %d", skip, end, end-skip, clk, (end-skip)/clk, phaseoff);
	//now begin to trim out ST so we can use normal demod cmds
	start = skip;
	size_t datalen = end - start;
	// check validity of datalen (should be even clock increments)  - use a tolerance of up to 1/8th a clock
	if ( clk - (datalen % clk) <= clk/8) {
		// padd the amount off - could be problematic...  but shouldn't happen often
		datalen += clk - (datalen % clk);
	} else if ( (datalen % clk) <= clk/8 ) {
		// padd the amount off - could be problematic...  but shouldn't happen often
		datalen -= datalen % clk;
	} else {
		if (g_debugMode==2) prnt("DEBUG STT: datalen not divisible by clk: %u %% %d = %d - quitting", datalen, clk, datalen % clk);
		return false;
	}
	// if datalen is less than one t55xx block - ERROR
	if (datalen/clk < 8*4) {
		if (g_debugMode==2) prnt("DEBUG STT: datalen is less than 1 full t55xx block - quitting");		
		return false;
	}
	size_t dataloc = start;
	if (buffer[dataloc-(clk*4)-(clk/4)] <= low && buffer[dataloc] <= low && buffer[dataloc-(clk*4)] >= high) {
		//we have low drift (and a low just before the ST and a low just after the ST) - compensate by backing up the start 
		for ( i=0; i <= (clk/4); ++i ) {
			if ( buffer[dataloc - (clk*4) - i] <= low ) {
				dataloc -= i;
				break;
			}
		}
	}
	
	size_t newloc = 0;
	i=0;
	if (g_debugMode==2) prnt("DEBUG STT: Starting STT trim - start: %d, datalen: %d ",dataloc, datalen);		
	bool firstrun = true;
	// warning - overwriting buffer given with raw wave data with ST removed...
	while ( dataloc < bufsize-(clk/2) ) {
		//compensate for long high at end of ST not being high due to signal loss... (and we cut out the start of wave high part)
		if (buffer[dataloc]<high && buffer[dataloc]>low && buffer[dataloc+clk/4]<high && buffer[dataloc+clk/4]>low) {
			for(i=0; i < clk/2-tol; ++i) {
				buffer[dataloc+i] = high+5;
			}
		} //test for small spike outlier (high between two lows) in the case of very strong waves
		if (buffer[dataloc] > low && buffer[dataloc+clk/4] <= low) {
			for(i=0; i < clk/4; ++i) {
				buffer[dataloc+i] = buffer[dataloc+clk/4];
			}
		}
		if (firstrun) {
			*stend = dataloc;
			*ststart = dataloc-(clk*4);
			firstrun=false;
		}
		for (i=0; i<datalen; ++i) {
			if (i+newloc < bufsize) {
				if (i+newloc < dataloc)
					buffer[i+newloc] = buffer[dataloc];

				dataloc++;				
			}
		}
		newloc += i;
		//skip next ST  -  we just assume it will be there from now on...
		if (g_debugMode==2) prnt("DEBUG STT: skipping STT at %d to %d", dataloc, dataloc+(clk*4));
		dataloc += clk*4;
	}
	*size = newloc;
	return true;
}

//by marshmellow
//take 11 10 01 11 00 and make 01100 ... miller decoding 
//check for phase errors - should never have half a 1 or 0 by itself and should never exceed 1111 or 0000 in a row
//decodes miller encoded binary
//NOTE  askrawdemod will NOT demod miller encoded ask unless the clock is manually set to 1/2 what it is detected as!
int millerRawDecode(uint8_t *bits, size_t *size, int invert) {
	if (*size < 16) return -1;
	
	uint16_t MaxBits = 512, errCnt = 0;
	size_t i, bitCnt = 0;
	uint8_t alignCnt = 0, curBit = bits[0], alignedIdx = 0, halfClkErr = 0;
	
	//find alignment, needs 4 1s or 0s to properly align
	for (i=1; i < *size-1; i++) {
		alignCnt = (bits[i] == curBit) ? alignCnt+1 : 0;
		curBit = bits[i];
		if (alignCnt == 4) break;
	}
	// for now error if alignment not found.  later add option to run it with multiple offsets...
	if (alignCnt != 4) {
		if (g_debugMode) prnt("ERROR MillerDecode: alignment not found so either your bits is not miller or your data does not have a 101 in it");
		return -1;
	}
	alignedIdx = (i-1) % 2;
	for (i = alignedIdx; i < *size-3; i += 2) {
		halfClkErr = (uint8_t)((halfClkErr << 1 | bits[i]) & 0xFF);
		if ( (halfClkErr & 0x7) == 5 || (halfClkErr & 0x7) == 2 || (i > 2 && (halfClkErr & 0x7) == 0) || (halfClkErr & 0x1F) == 0x1F) {
			errCnt++;
			bits[bitCnt++] = 7;
			continue;
		}
		bits[bitCnt++] = bits[i] ^ bits[i+1] ^ invert;

		if (bitCnt > MaxBits) break;
	}
	*size = bitCnt;
	return errCnt;
}

//by marshmellow
//take 01 or 10 = 1 and 11 or 00 = 0
//check for phase errors - should never have 111 or 000 should be 01001011 or 10110100 for 1010
//decodes biphase or if inverted it is AKA conditional dephase encoding AKA differential manchester encoding
int BiphaseRawDecode(uint8_t *bits, size_t *size, int *offset, int invert) {
	//sanity check
	if (*size < 51) return -1;
	
	uint16_t bitnum = 0;
	uint16_t errCnt = 0;
	size_t i = *offset;
	uint16_t maxbits = 512;

	//check for phase change faults - skip one sample if faulty
	bool offsetA = true, offsetB = true;
	for (; i < *offset+48; i += 2){
		if (bits[i+1] == bits[i+2]) offsetA = false;
		if (bits[i+2] == bits[i+3]) offsetB = false;
	}
	if (!offsetA && offsetB) ++*offset;
	
	for (i = *offset; i < *size-3; i += 2){
		//check for phase error
		if (bits[i+1] == bits[i+2]) {
			bits[bitnum++] = 7;
			errCnt++;
		}
		if((bits[i]==1 && bits[i+1]==0) || (bits[i]==0 && bits[i+1]==1)){
			bits[bitnum++] = 1 ^ invert;
		} else if((bits[i]==0 && bits[i+1]==0) || (bits[i]==1 && bits[i+1]==1)){
			bits[bitnum++] = invert;
		} else {
			bits[bitnum++] = 7;
			errCnt++;
		}
		if (bitnum > maxbits) break;
	}
	*size = bitnum;
	return errCnt;
}

//by marshmellow
//take 10 and 01 and manchester decode
//run through 2 times and take least errCnt
int manrawdecode(uint8_t *bits, size_t *size, uint8_t invert, uint8_t *alignPos){

	// sanity check
	if (*size < 16) return -1;
	
	int errCnt = 0, bestErr = 1000;
	uint16_t bitnum = 0, maxBits = 512, bestRun = 0;
	size_t i, k;

	//find correct start position [alignment]
	for (k = 0; k < 2; ++k){
		for (i = k; i < *size-3; i += 2) {
			if (bits[i] == bits[i+1])
				errCnt++;
		}
		if (bestErr > errCnt){
			bestErr = errCnt;
			bestRun = k;
		}
		errCnt = 0;
	}
	*alignPos = bestRun;
	//decode
	for (i = bestRun; i < *size-3; i += 2){
		if (bits[i] == 1 && (bits[i+1] == 0)){
			bits[bitnum++] = invert;
		} else if ((bits[i] == 0) && bits[i+1] == 1){
			bits[bitnum++] = invert^1;
		} else {
			bits[bitnum++] = 7;
		}
		if (bitnum > maxBits) break;
	}
	*size = bitnum;
	return bestErr;
}

//by marshmellow
//demodulates strong heavily clipped samples
//RETURN: num of errors.  if 0, is ok.
int cleanAskRawDemod(uint8_t *bits, size_t *size, int clk, int invert, int high, int low, int *startIdx) {
	*startIdx = 0;
	size_t bitCnt=0, smplCnt=1, errCnt=0;
	bool waveHigh = (bits[0] >= high);
	
	for (size_t i=1; i < *size; i++){
		if (bits[i] >= high && waveHigh){
			smplCnt++;
		} else if (bits[i] <= low && !waveHigh){
			smplCnt++;
		} else { //transition
			if ((bits[i] >= high && !waveHigh) || (bits[i] <= low && waveHigh)){

				if (smplCnt > clk-(clk/4)-1) { //full clock
					if (smplCnt > clk + (clk/4)+1) { //too many samples
						errCnt++;
						if (g_debugMode==2) prnt("DEBUG:(cleanAskRawDemod) ASK Modulation Error at: %u", i);
						bits[bitCnt++] = 7;
					} else if (waveHigh) {
						bits[bitCnt++] = invert;
						bits[bitCnt++] = invert;
					} else if (!waveHigh) {
						bits[bitCnt++] = invert ^ 1;
						bits[bitCnt++] = invert ^ 1;
					}
					if (*startIdx==0)
						*startIdx = i-clk;
					waveHigh = !waveHigh;  
					smplCnt = 0;
				} else if (smplCnt > (clk/2) - (clk/4)-1) { //half clock
					if (waveHigh) {
						bits[bitCnt++] = invert;
					} else if (!waveHigh) {
						bits[bitCnt++] = invert ^ 1;
					}
					if (*startIdx==0)
						*startIdx = i-(clk/2);
					waveHigh = !waveHigh;  
					smplCnt = 0;
				} else {
					smplCnt++;
					//transition bit oops
				}
			} else { //haven't hit new high or new low yet
				smplCnt++;
			}
		}
	}
	*size = bitCnt;
	return errCnt;
}

//by marshmellow
//attempts to demodulate ask modulations, askType == 0 for ask/raw, askType==1 for ask/manchester
int askdemod_ext(uint8_t *bits, size_t *size, int *clk, int *invert, int maxErr, uint8_t amp, uint8_t askType, int *startIdx) {
	if (*size==0) return -1;
	int start = DetectASKClock(bits, *size, clk, maxErr); //clock default
	if (*clk==0 || start < 0) return -3;
	if (*invert != 1) *invert = 0;
	if (amp==1) askAmp(bits, *size);
	if (g_debugMode==2) prnt("DEBUG ASK: clk %d, beststart %d, amp %d", *clk, start, amp);
		
	//start pos from detect ask clock is 1/2 clock offset
	// NOTE: can be negative (demod assumes rest of wave was there)
	*startIdx = start - (*clk/2); 
	uint16_t initLoopMax = 1024;
	if (initLoopMax > *size) initLoopMax = *size;
	// Detect high and lows
	//25% clip in case highs and lows aren't clipped [marshmellow]
	int high, low;
	if (getHiLo(bits, initLoopMax, &high, &low, 75, 75) < 1) 
		return -2; //just noise

	size_t errCnt = 0;
	// if clean clipped waves detected run alternate demod
	if (DetectCleanAskWave(bits, *size, high, low)) {

		if (g_debugMode==2) prnt("DEBUG ASK: Clean Wave Detected - using clean wave demod");
		
		errCnt = cleanAskRawDemod(bits, size, *clk, *invert, high, low, startIdx);

		if (askType) { //ask/manchester
			uint8_t alignPos = 0;
			errCnt = manrawdecode(bits, size, 0, &alignPos);
			*startIdx += *clk/2 * alignPos;
			if (g_debugMode) 
				prnt("DEBUG: (askdemod_ext) CLEAN: startIdx %i, alignPos %u", *startIdx, alignPos);
		} 
		return errCnt;
	}
	if (g_debugMode) prnt("DEBUG: (askdemod_ext) Weak wave detected: startIdx %i", *startIdx);
	
	int lastBit;  //set first clock check - can go negative
	size_t i, bitnum = 0;     //output counter
	uint8_t midBit = 0;
	uint8_t tol = 0;  //clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
	if (*clk <= 32) tol = 1;    //clock tolerance may not be needed anymore currently set to + or - 1 but could be increased for poor waves or removed entirely
	size_t MaxBits = 3072;    //max bits to collect
	lastBit = start - *clk;

	for (i = start; i < *size; ++i) {
		if (i-lastBit >= *clk-tol){
			if (bits[i] >= high) {
				bits[bitnum++] = *invert;
			} else if (bits[i] <= low) {
				bits[bitnum++] = *invert ^ 1;
			} else if (i-lastBit >= *clk+tol) {
				if (bitnum > 0) {
					if (g_debugMode==2) prnt("DEBUG: (askdemod_ext) Modulation Error at: %u", i);
					bits[bitnum++]=7;
					errCnt++;						
				} 
			} else { //in tolerance - looking for peak
				continue;
			}
			midBit = 0;
			lastBit += *clk;
		} else if (i-lastBit >= (*clk/2-tol) && !midBit && !askType){
			if (bits[i] >= high) {
				bits[bitnum++] = *invert;
			} else if (bits[i] <= low) {
				bits[bitnum++] = *invert ^ 1;
			} else if (i-lastBit >= *clk/2+tol) {
				bits[bitnum] = bits[bitnum-1];
				bitnum++;
			} else { //in tolerance - looking for peak
				continue;
			}
			midBit = 1;
		}
		if (bitnum >= MaxBits) break;
	}
	*size = bitnum;
	return errCnt;
}

int askdemod(uint8_t *bits, size_t *size, int *clk, int *invert, int maxErr, uint8_t amp, uint8_t askType) {
	int start = 0;
	return askdemod_ext(bits, size, clk, invert, maxErr, amp, askType, &start);
}

// by marshmellow - demodulate NRZ wave - requires a read with strong signal
// peaks invert bit (high=1 low=0) each clock cycle = 1 bit determined by last peak
int nrzRawDemod(uint8_t *dest, size_t *size, int *clk, int *invert, int *startIdx) {
	if (signalprop.isnoise) return -1;
	
	size_t clkStartIdx = 0;
	*clk = DetectNRZClock(dest, *size, *clk, &clkStartIdx);
	if (*clk == 0) return -2;
	
	size_t i, gLen = 4096;
	if (gLen > *size) 
		gLen = *size-20;
	
	int high, low;
	if (getHiLo(dest, gLen, &high, &low, 75, 75) < 1) return -3; //25% fuzz on high 25% fuzz on low

	uint8_t bit=0;
	//convert wave samples to 1's and 0's
	for(i=20; i < *size-20; i++){
		if (dest[i] >= high) bit = 1;
		if (dest[i] <= low)  bit = 0;
		dest[i] = bit;
	}
	//now demod based on clock (rf/32 = 32 1's for one 1 bit, 32 0's for one 0 bit) 
	size_t lastBit = 0;
	size_t numBits = 0;
	for(i=21; i < *size-20; i++) {
		//if transition detected or large number of same bits - store the passed bits
		if (dest[i] != dest[i-1] || (i-lastBit) == (10 * *clk)) {
			memset(dest+numBits, dest[i-1] ^ *invert, (i - lastBit + (*clk/4)) / *clk);
			numBits += (i - lastBit + (*clk/4)) / *clk;
			if (lastBit == 0) {
				*startIdx = i - (numBits * *clk);
				if (g_debugMode==2) prnt("DEBUG NRZ: startIdx %i", *startIdx);
			}
			lastBit = i-1;
		}
	}
	*size = numBits;
	return 0;
}

//translate wave to 11111100000 (1 for each short wave [higher freq] 0 for each long wave [lower freq])
size_t fsk_wave_demod(uint8_t *dest, size_t size, uint8_t fchigh, uint8_t fclow, int *startIdx) {
	
	if ( size < 1024 ) return 0; // not enough samples
	
	if (fchigh == 0) fchigh = 10;
	if (fclow == 0) fclow = 8;

	//set the threshold close to 0 (graph) or 128 std to avoid static
	size_t preLastSample = 0;
	size_t LastSample = 0;
	size_t currSample = 0;
	size_t last_transition = 0;
	size_t idx = 1;
	size_t numBits = 0;
	
	//find start of modulating data in trace 	
	idx = findModStart(dest, size, fchigh);
	// Need to threshold first sample
	dest[0] = (dest[idx] < FSK_PSK_THRESHOLD) ? 0 : 1;
	
	last_transition = idx;
	idx++;
	
	// Definition:  cycles between consecutive lo-hi transitions
	// Lets define some expected lengths. FSK1 is easier since it has bigger differences between.
	// FSK1 8/5 
	// 50/8 = 6		| 40/8 = 5  | 64/8 = 8
	// 50/5 = 10	| 40/5 = 8	| 64/5 = 12

	// FSK2 10/8
	// 50/10 = 5	| 40/10 = 4 | 64/10 = 6
	// 50/8  = 6	| 40/8  = 5 | 64/8  = 8
	
	// count cycles between consecutive lo-hi transitions,
	// in practice due to noise etc we may end up with anywhere
	// To allow fuzz would mean  +-1 on expected cycle width.
	// FSK1 8/5
	// 50/8 = 6 (5-7)	| 40/8 = 5 (4-6)	| 64/8 = 8 (7-9)
	// 50/5 = 10 (9-11)	| 40/5 = 8 (7-9)	| 64/5 = 12 (11-13)

	// FSK2 10/8
	// 50/10 = 5 (4-6)	| 40/10 = 4 (3-5)	| 64/10 = 6 (5-7)
	// 50/8  = 6 (5-7)	| 40/8  = 5 (4-6)	| 64/8  = 8	(7-9)
	//
	// It easy to see to the overgaping, but luckily we the group value also,  like 1111000001111
	// to separate between which bit to demodulate to.

	// process: 
	// count width from 0-1 transition to  1-0.  
	// determine the width is withing FUZZ_min and FUZZ_max tolerances
	// width should be divided with exp_one.  i:e 6+7+6+2=21,  21/5 = 4, 
	// the 1-0 to 0-1  width should be divided with exp_zero.   Ie: 3+5+6+7 = 21/6 = 3	
	
	for(; idx < size-20; idx++) {
		
		// threshold current value
		dest[idx] = (dest[idx] < FSK_PSK_THRESHOLD) ? 0 : 1;

		// Check for 0->1 transition
		if (dest[idx-1] < dest[idx]) {
			preLastSample = LastSample;
			LastSample = currSample;
			currSample = idx-last_transition;
			if (currSample < (fclow-2)){            //0-5 = garbage noise (or 0-3)
				//do nothing with extra garbage
			} else if (currSample < (fchigh-1)) {           //6-8 = 8 sample waves  (or 3-6 = 5)
				//correct previous 9 wave surrounded by 8 waves (or 6 surrounded by 5)
				if (numBits > 1 && LastSample > (fchigh-2) && (preLastSample < (fchigh-1))){
					dest[numBits-1]=1;
				}
				dest[numBits++]=1;
				
				
				if (numBits > 0 && *startIdx == 0)
					*startIdx = idx - fclow;
				
			} else if (currSample > (fchigh+1) && numBits < 3) { //12 + and first two bit = unusable garbage
				//do nothing with beginning garbage and reset..  should be rare..
				numBits = 0; 
			} else if (currSample == (fclow+1) && LastSample == (fclow-1)) { // had a 7 then a 9 should be two 8's (or 4 then a 6 should be two 5's)
				dest[numBits++]=1;
				if (numBits > 0 && *startIdx == 0) {
					*startIdx = idx - fclow;
				}
			} else {                                        //9+ = 10 sample waves (or 6+ = 7)
				dest[numBits++]=0;
					if (numBits > 0 && *startIdx == 0) {
						*startIdx = idx - fchigh;
					}
			}
			last_transition = idx;
		}
	}
	return numBits; //Actually, it returns the number of bytes, but each byte represents a bit: 1 or 0
}

//translate 11111100000 to 10
//rfLen = clock, fchigh = larger field clock, fclow = smaller field clock
size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t clk, uint8_t invert, uint8_t fchigh, uint8_t fclow, int *startIdx) {

	uint8_t lastval = dest[0];
	size_t i = 0;
	size_t numBits = 0;
	uint32_t n = 1;
	uint8_t hclk = clk/2;
	
	for( i = 1; i < size; i++) {
		n++;
		if (dest[i] == lastval) continue; //skip until we hit a transition
		
		//find out how many bits (n) we collected (use 1/2 clk tolerance)
		
		if (dest[i-1] == 1)
		//if lastval was 1, we have a 1->0 crossing
			n = (n * fclow + hclk) / clk;
		else 
			// 0->1 crossing 
			n = (n * fchigh + hclk) / clk; 

		if (n == 0) 
			n = 1;

		//first transition - save startidx
		if (numBits == 0) {
			if (lastval == 1) {  //high to low
				*startIdx += (fclow * i) - (n*clk);
				if (g_debugMode == 2) prnt("DEBUG (aggregate_bits) FSK startIdx %i, fclow*idx %i, n*clk %u", *startIdx, fclow*i, n*clk);
			} else {
				*startIdx += (fchigh * i) - (n*clk);
				if (g_debugMode == 2) prnt("DEBUG (aggregate_bits) FSK startIdx %i, fchigh*idx %i, n*clk %u", *startIdx, fchigh*i, n*clk);
			}
		}

		//add to our destination the bits we collected		
		memset(dest+numBits, dest[i-1] ^ invert , n);

		numBits += n;
		n = 0;
		lastval = dest[i];

	}//end for
	
	// if valid extra bits at the end were all the same frequency - add them in
	if (n > clk/fchigh) {
		if (dest[i-2] == 1) {
			n = (n * fclow + clk/2) / clk;
		} else {
			n = (n * fchigh + clk/2) / clk;
		}
		memset(dest+numBits, dest[i-1] ^ invert , n);
		numBits += n;
	}
	return numBits;
}

//by marshmellow  (from holiman's base)
// full fsk demod from GraphBuffer wave to decoded 1s and 0s (no mandemod)
size_t fskdemod(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow, int *start_idx) {
	if (signalprop.isnoise) return 0;
	// FSK demodulator
	size = fsk_wave_demod(dest, size, fchigh, fclow, start_idx);
	size = aggregate_bits(dest, size, rfLen, invert, fchigh, fclow, start_idx);
	return size;
}

// by marshmellow
// convert psk1 demod to psk2 demod
// only transition waves are 1s
//TODO: Iceman - hard coded value 7,  should be #define
void psk1TOpsk2(uint8_t *bits, size_t size) {
	uint8_t lastbit = bits[0];
	for (size_t i = 1; i < size; i++){
		//ignore errors		
		if (bits[i] == 7) continue;
			
		if (lastbit != bits[i]){
			lastbit = bits[i];
			bits[i] = 1;
		} else {
			bits[i] = 0;
		}
	}
}

// by marshmellow
// convert psk2 demod to psk1 demod
// from only transition waves are 1s to phase shifts change bit
void psk2TOpsk1(uint8_t *bits, size_t size) {
	uint8_t phase = 0;
	for (size_t i = 0; i < size; i++){
		if (bits[i] == 1){
			phase ^= 1;
		}
		bits[i] = phase;
	}
}

//by marshmellow - demodulate PSK1 wave 
//uses wave lengths (# Samples) 
//TODO: Iceman - hard coded value 7,  should be #define
int pskRawDemod_ext(uint8_t *dest, size_t *size, int *clock, int *invert, int *startIdx) {
	
	// sanity check
	if (*size < 170) return -1;

	uint8_t curPhase = *invert;
	uint8_t fc=0;
	size_t i=0, numBits=0, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0;
	uint16_t fullWaveLen=0, waveLenCnt=0, avgWaveVal=0;
	uint16_t errCnt=0, errCnt2=0;

	*clock = DetectPSKClock(dest, *size, *clock, &firstFullWave, &curPhase, &fc);
	if (*clock <= 0) return -1;
	//if clock detect found firstfullwave...
	uint16_t tol = fc/2;
	if (firstFullWave == 0) {
		//find start of modulating data in trace 
		i = findModStart(dest, *size, fc);
		//find first phase shift
		firstFullWave = pskFindFirstPhaseShift(dest, *size, &curPhase, i, fc, &fullWaveLen);
		if (firstFullWave == 0) {
			// no phase shift detected - could be all 1's or 0's - doesn't matter where we start
			// so skip a little to ensure we are past any Start Signal
			firstFullWave = 160;
			memset(dest, curPhase, firstFullWave / *clock);
		} else {
			memset(dest, curPhase^1, firstFullWave / *clock);
		}
	} else {
		memset(dest, curPhase^1, firstFullWave / *clock);
	}
	//advance bits
	numBits += (firstFullWave / *clock);
	*startIdx = firstFullWave - (*clock * numBits)+2;
	//set start of wave as clock align
	lastClkBit = firstFullWave;
	if (g_debugMode==2) prnt("DEBUG PSK: firstFullWave: %u, waveLen: %u, startIdx %i",firstFullWave,fullWaveLen, *startIdx);
	if (g_debugMode == 2) prnt("DEBUG PSK: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit, fc);
	waveStart = 0;
	dest[numBits++] = curPhase; //set first read bit
	for (i = firstFullWave + fullWaveLen - 1; i < *size-3; i++){
		//top edge of wave = start of new wave 
		if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
			if (waveStart == 0) {
				waveStart = i+1;
				waveLenCnt = 0;
				avgWaveVal = dest[i+1];
			} else { //waveEnd
				waveEnd = i+1;
				waveLenCnt = waveEnd-waveStart;
				if (waveLenCnt > fc){  
					//this wave is a phase shift
					//prnt("DEBUG: phase shift at: %d, len: %d, nextClk: %d, i: %d, fc: %d",waveStart,waveLenCnt,lastClkBit+*clock-tol,i+1,fc);
					if (i+1 >= lastClkBit + *clock - tol){ //should be a clock bit
						curPhase ^= 1;
						dest[numBits++] = curPhase;
						lastClkBit += *clock;
					} else if (i < lastClkBit+10+fc){
						//noise after a phase shift - ignore
					} else { //phase shift before supposed to based on clock
						errCnt++;
						dest[numBits++] = 7;
					}
				} 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 += dest[i+1];
					continue;
				}
				avgWaveVal = 0;
				waveStart = i+1;
			}
		}
		avgWaveVal += dest[i+1];
	}
	*size = numBits;
	return errCnt;
}

int pskRawDemod(uint8_t *dest, size_t *size, int *clock, int *invert) {
	int start_idx = 0;
	return pskRawDemod_ext(dest, size, clock, invert, &start_idx);
}


//**********************************************************************************************
//-----------------Tag format detection section-------------------------------------------------
//**********************************************************************************************


// by marshmellow
// FSK Demod then try to locate an AWID ID
int detectAWID(uint8_t *dest, size_t *size, int *waveStartIdx) {
	//make sure buffer has enough data (96bits * 50clock samples)
	if (*size < 96*50) return -1;

	if (signalprop.isnoise) return -2;

	// FSK2a demodulator  clock 50, invert 1, fcHigh 10, fcLow 8
	*size = fskdemod(dest, *size, 50, 1, 10, 8, waveStartIdx); //awid fsk2a

	//did we get a good demod?
	if (*size < 96) return -3;

	size_t start_idx = 0;
	uint8_t preamble[] = {0,0,0,0,0,0,0,1};
	if (!preambleSearch(dest, preamble, sizeof(preamble), size, &start_idx))
		return -4; //preamble not found
	
	// wrong size?  (between to preambles)
	if (*size != 96) return -5;
	
	return (int)start_idx;
}

//by marshmellow
//takes 1s and 0s and searches for EM410x format - output EM ID
int Em410xDecode(uint8_t *bits, size_t *size, size_t *start_idx, uint32_t *hi, uint64_t *lo) {
	// sanity check
	if (bits[1] > 1) return -1; 
	if (*size < 64) return -2;	

	uint8_t fmtlen;
	*start_idx = 0;
	
	// preamble 0111111111
	// include 0 in front to help get start pos
	uint8_t preamble[] = {0,1,1,1,1,1,1,1,1,1};
	if (!preambleSearch(bits, preamble, sizeof(preamble), size, start_idx))
		return -4;

	// (iceman) if the preamble doesn't find two occuriences, this identification fails.
	fmtlen = (*size == 128) ? 22 : 10;

	//skip last 4bit parity row for simplicity
	*size = removeParity(bits, *start_idx + sizeof(preamble), 5, 0, fmtlen * 5);  
	
	switch (*size) {
	   case 40: { 
	    // std em410x format
		*hi = 0;
		*lo = ((uint64_t)(bytebits_to_byte(bits, 8)) << 32) | (bytebits_to_byte(bits + 8, 32));
		break;
	    } 
	    case 88:  { 
	    // long em format
		*hi = (bytebits_to_byte(bits, 24)); 
		*lo = ((uint64_t)(bytebits_to_byte(bits + 24, 32)) << 32) | (bytebits_to_byte(bits + 24 + 32, 32));
		break;
	    } 
	    default: return -6;	
	}
	return 1;
}

// loop to get raw HID waveform then FSK demodulate the TAG ID from it
int HIDdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo, int *waveStartIdx) {
	//make sure buffer has data
	if (*size < 96*50) return -1;
	
	if (signalprop.isnoise) return -2;
		
	// zero mean data
	int i, accum = 0;
	for (i = 10; i < *size; ++i)
		accum += dest[i];
	
	accum /= (*size - 10);
	
	for (i = 0; i < *size; ++i)
		dest[i] -= accum;
	
	// FSK demodulator  fsk2a so invert and fc/10/8
	*size = fskdemod(dest, *size, 50, 1, 10, 8, waveStartIdx); //hid fsk2a

	//did we get a good demod?
	if (*size < 96*2) return -3;

	// 00011101 bit pattern represent start of frame, 01 pattern represents a 0 and 10 represents a 1
	size_t start_idx = 0;	
	uint8_t preamble[] = {0,0,0,1,1,1,0,1};
	if (!preambleSearch(dest, preamble, sizeof(preamble), size, &start_idx)) 
		return -4; //preamble not found

	// wrong size?  (between to preambles)
	//if (*size != 96) return -5;
	
	size_t num_start = start_idx + sizeof(preamble);
	// final loop, go over previously decoded FSK data and manchester decode into usable tag ID
	for (size_t idx = num_start; (idx - num_start) < *size - sizeof(preamble); idx += 2) {
		if (dest[idx] == dest[idx+1]){
			return -5; //not manchester data
		}
		*hi2 = (*hi2 << 1) | (*hi >> 31);
		*hi = (*hi << 1) | (*lo >> 31);
		//Then, shift in a 0 or one into low
		*lo <<= 1;
		if (dest[idx] && !dest[idx+1])  // 1 0
			*lo |= 1;
		else // 0 1
			*lo |= 0;
	}
	return (int)start_idx;
}

// Find IDTEC PSK1, RF  Preamble == 0x4944544B, Demodsize 64bits
// by iceman
int detectIdteck(uint8_t *dest, size_t *size) {
	//make sure buffer has data
	if (*size < 64*2) return -1;	
	
	if (signalprop.isnoise) return -2;
	
	size_t start_idx = 0;
	uint8_t preamble[] = {0,1,0,0,1,0,0,1,0,1,0,0,0,1,0,0,0,1,0,1,0,1,0,0,0,1,0,0,1,0,1,1};
	
	//preamble not found
	if (!preambleSearch(dest, preamble, sizeof(preamble), size, &start_idx))
		return -3; 
	
	 // wrong demoded size
	if (*size != 64) return -4;
	return (int)start_idx;
}

int detectIOProx(uint8_t *dest, size_t *size, int *waveStartIdx) {
	//make sure buffer has data
	if (*size < 66*64) return -1;
	
	if (signalprop.isnoise) return -2;
	
	// FSK demodulator  RF/64, fsk2a so invert, and fc/10/8
	*size = fskdemod(dest, *size, 64, 1, 10, 8, waveStartIdx);  //io fsk2a
	
	//did we get enough demod data?
	if (*size < 64) return -3;
	
	//Index map
	//0           10          20          30          40          50          60
	//|           |           |           |           |           |           |
	//01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
	//-----------------------------------------------------------------------------
	//00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
	//
	//XSF(version)facility:codeone+codetwo

	size_t start_idx = 0;
	uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,1};
	if (!preambleSearch(dest, preamble, sizeof(preamble), size, &start_idx))
		return -4; //preamble not found

	// wrong size?  (between to preambles)
	if (*size != 64) return -5;
	
	if (  !dest[start_idx + 8] 
		&& dest[start_idx + 17] == 1 
		&& dest[start_idx + 26] == 1 
		&& dest[start_idx + 35] == 1
		&& dest[start_idx + 44] == 1 
		&& dest[start_idx + 53] == 1) {
		//confirmed proper separator bits found
		//return start position
		return (int) start_idx;
	}
	return -6;
}