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1 //-----------------------------------------------------------------------------
2 // Copyright (C) 2014
3 //
4 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
5 // at your option, any later version. See the LICENSE.txt file for the text of
6 // the license.
7 //-----------------------------------------------------------------------------
8 // Low frequency demod/decode commands
9 //-----------------------------------------------------------------------------
10
11 #include <stdlib.h>
12 #include "lfdemod.h"
13 #include <string.h>
14
15 //to allow debug print calls when used not on device
16 void dummy(char *fmt, ...){}
17
18 #ifndef ON_DEVICE
19 #include "ui.h"
20 #include "cmdparser.h"
21 #include "cmddata.h"
22 #define prnt PrintAndLog
23 #else
24 uint8_t g_debugMode=0;
25 #define prnt dummy
26 #endif
27
28 uint8_t justNoise(uint8_t *BitStream, size_t size)
29 {
30 static const uint8_t THRESHOLD = 123;
31 //test samples are not just noise
32 uint8_t justNoise1 = 1;
33 for(size_t idx=0; idx < size && justNoise1 ;idx++){
34 justNoise1 = BitStream[idx] < THRESHOLD;
35 }
36 return justNoise1;
37 }
38
39 //by marshmellow
40 //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
41 int getHiLo(uint8_t *BitStream, size_t size, int *high, int *low, uint8_t fuzzHi, uint8_t fuzzLo)
42 {
43 *high=0;
44 *low=255;
45 // get high and low thresholds
46 for (size_t i=0; i < size; i++){
47 if (BitStream[i] > *high) *high = BitStream[i];
48 if (BitStream[i] < *low) *low = BitStream[i];
49 }
50 if (*high < 123) return -1; // just noise
51 *high = ((*high-128)*fuzzHi + 12800)/100;
52 *low = ((*low-128)*fuzzLo + 12800)/100;
53 return 1;
54 }
55
56 // by marshmellow
57 // pass bits to be tested in bits, length bits passed in bitLen, and parity type (even=0 | odd=1) in pType
58 // returns 1 if passed
59 uint8_t parityTest(uint32_t bits, uint8_t bitLen, uint8_t pType)
60 {
61 uint8_t ans = 0;
62 for (uint8_t i = 0; i < bitLen; i++){
63 ans ^= ((bits >> i) & 1);
64 }
65 //PrintAndLog("DEBUG: ans: %d, ptype: %d",ans,pType);
66 return (ans == pType);
67 }
68
69 // by marshmellow
70 // takes a array of binary values, start position, length of bits per parity (includes parity bit),
71 // Parity Type (1 for odd; 0 for even; 2 for Always 1's; 3 for Always 0's), and binary Length (length to run)
72 size_t removeParity(uint8_t *BitStream, size_t startIdx, uint8_t pLen, uint8_t pType, size_t bLen)
73 {
74 uint32_t parityWd = 0;
75 size_t j = 0, bitCnt = 0;
76 for (int word = 0; word < (bLen); word+=pLen){
77 for (int bit=0; bit < pLen; bit++){
78 parityWd = (parityWd << 1) | BitStream[startIdx+word+bit];
79 BitStream[j++] = (BitStream[startIdx+word+bit]);
80 }
81 j--; // overwrite parity with next data
82 // if parity fails then return 0
83 switch (pType) {
84 case 3: if (BitStream[j]==1) {return 0;} break; //should be 0 spacer bit
85 case 2: if (BitStream[j]==0) {return 0;} break; //should be 1 spacer bit
86 default: if (parityTest(parityWd, pLen, pType) == 0) {return 0;} break; //test parity
87 }
88 bitCnt+=(pLen-1);
89 parityWd = 0;
90 }
91 // if we got here then all the parities passed
92 //return ID start index and size
93 return bitCnt;
94 }
95
96 // by marshmellow
97 // takes a array of binary values, length of bits per parity (includes parity bit),
98 // Parity Type (1 for odd; 0 for even; 2 Always 1's; 3 Always 0's), and binary Length (length to run)
99 // Make sure *dest is long enough to store original sourceLen + #_of_parities_to_be_added
100 size_t addParity(uint8_t *BitSource, uint8_t *dest, uint8_t sourceLen, uint8_t pLen, uint8_t pType)
101 {
102 uint32_t parityWd = 0;
103 size_t j = 0, bitCnt = 0;
104 for (int word = 0; word < sourceLen; word+=pLen-1) {
105 for (int bit=0; bit < pLen-1; bit++){
106 parityWd = (parityWd << 1) | BitSource[word+bit];
107 dest[j++] = (BitSource[word+bit]);
108 }
109 // if parity fails then return 0
110 switch (pType) {
111 case 3: dest[j++]=0; break; // marker bit which should be a 0
112 case 2: dest[j++]=1; break; // marker bit which should be a 1
113 default:
114 dest[j++] = parityTest(parityWd, pLen-1, pType) ^ 1;
115 break;
116 }
117 bitCnt += pLen;
118 parityWd = 0;
119 }
120 // if we got here then all the parities passed
121 //return ID start index and size
122 return bitCnt;
123 }
124
125 uint32_t bytebits_to_byte(uint8_t *src, size_t numbits)
126 {
127 uint32_t num = 0;
128 for(int i = 0 ; i < numbits ; i++)
129 {
130 num = (num << 1) | (*src);
131 src++;
132 }
133 return num;
134 }
135
136 //least significant bit first
137 uint32_t bytebits_to_byteLSBF(uint8_t *src, size_t numbits)
138 {
139 uint32_t num = 0;
140 for(int i = 0 ; i < numbits ; i++)
141 {
142 num = (num << 1) | *(src + (numbits-(i+1)));
143 }
144 return num;
145 }
146
147 //by marshmellow
148 //search for given preamble in given BitStream and return success=1 or fail=0 and startIndex and length
149 uint8_t preambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx)
150 {
151 uint8_t foundCnt=0;
152 for (int idx=0; idx < *size - pLen; idx++){
153 if (memcmp(BitStream+idx, preamble, pLen) == 0){
154 //first index found
155 foundCnt++;
156 if (foundCnt == 1){
157 *startIdx = idx;
158 }
159 if (foundCnt == 2){
160 *size = idx - *startIdx;
161 return 1;
162 }
163 }
164 }
165 return 0;
166 }
167
168 //by marshmellow
169 //takes 1s and 0s and searches for EM410x format - output EM ID
170 uint8_t Em410xDecode(uint8_t *BitStream, size_t *size, size_t *startIdx, uint32_t *hi, uint64_t *lo)
171 {
172 //no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
173 // otherwise could be a void with no arguments
174 //set defaults
175 uint32_t i = 0;
176 if (BitStream[1]>1) return 0; //allow only 1s and 0s
177
178 // 111111111 bit pattern represent start of frame
179 // include 0 in front to help get start pos
180 uint8_t preamble[] = {0,1,1,1,1,1,1,1,1,1};
181 uint32_t idx = 0;
182 uint32_t parityBits = 0;
183 uint8_t errChk = 0;
184 uint8_t FmtLen = 10;
185 *startIdx = 0;
186 errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, startIdx);
187 if (errChk == 0 || *size < 64) return 0;
188 if (*size > 64) FmtLen = 22;
189 *startIdx += 1; //get rid of 0 from preamble
190 idx = *startIdx + 9;
191 for (i=0; i<FmtLen; i++){ //loop through 10 or 22 sets of 5 bits (50-10p = 40 bits or 88 bits)
192 parityBits = bytebits_to_byte(BitStream+(i*5)+idx,5);
193 //check even parity - quit if failed
194 if (parityTest(parityBits, 5, 0) == 0) return 0;
195 //set uint64 with ID from BitStream
196 for (uint8_t ii=0; ii<4; ii++){
197 *hi = (*hi << 1) | (*lo >> 63);
198 *lo = (*lo << 1) | (BitStream[(i*5)+ii+idx]);
199 }
200 }
201 if (errChk != 0) return 1;
202 //skip last 5 bit parity test for simplicity.
203 // *size = 64 | 128;
204 return 0;
205 }
206
207 //by marshmellow
208 //demodulates strong heavily clipped samples
209 int cleanAskRawDemod(uint8_t *BinStream, size_t *size, int clk, int invert, int high, int low)
210 {
211 size_t bitCnt=0, smplCnt=0, errCnt=0;
212 uint8_t waveHigh = 0;
213 for (size_t i=0; i < *size; i++){
214 if (BinStream[i] >= high && waveHigh){
215 smplCnt++;
216 } else if (BinStream[i] <= low && !waveHigh){
217 smplCnt++;
218 } else { //transition
219 if ((BinStream[i] >= high && !waveHigh) || (BinStream[i] <= low && waveHigh)){
220 if (smplCnt > clk-(clk/4)-1) { //full clock
221 if (smplCnt > clk + (clk/4)+1) { //too many samples
222 errCnt++;
223 if (g_debugMode==2) prnt("DEBUG ASK: Modulation Error at: %u", i);
224 BinStream[bitCnt++]=7;
225 } else if (waveHigh) {
226 BinStream[bitCnt++] = invert;
227 BinStream[bitCnt++] = invert;
228 } else if (!waveHigh) {
229 BinStream[bitCnt++] = invert ^ 1;
230 BinStream[bitCnt++] = invert ^ 1;
231 }
232 waveHigh ^= 1;
233 smplCnt = 0;
234 } else if (smplCnt > (clk/2) - (clk/4)-1) {
235 if (waveHigh) {
236 BinStream[bitCnt++] = invert;
237 } else if (!waveHigh) {
238 BinStream[bitCnt++] = invert ^ 1;
239 }
240 waveHigh ^= 1;
241 smplCnt = 0;
242 } else if (!bitCnt) {
243 //first bit
244 waveHigh = (BinStream[i] >= high);
245 smplCnt = 1;
246 } else {
247 smplCnt++;
248 //transition bit oops
249 }
250 } else { //haven't hit new high or new low yet
251 smplCnt++;
252 }
253 }
254 }
255 *size = bitCnt;
256 return errCnt;
257 }
258
259 //by marshmellow
260 void askAmp(uint8_t *BitStream, size_t size)
261 {
262 uint8_t Last = 128;
263 for(size_t i = 1; i<size; i++){
264 if (BitStream[i]-BitStream[i-1]>=30) //large jump up
265 Last = 255;
266 else if(BitStream[i-1]-BitStream[i]>=20) //large jump down
267 Last = 0;
268
269 BitStream[i-1] = Last;
270 }
271 return;
272 }
273
274 //by marshmellow
275 //attempts to demodulate ask modulations, askType == 0 for ask/raw, askType==1 for ask/manchester
276 int askdemod(uint8_t *BinStream, size_t *size, int *clk, int *invert, int maxErr, uint8_t amp, uint8_t askType)
277 {
278 if (*size==0) return -1;
279 int start = DetectASKClock(BinStream, *size, clk, maxErr); //clock default
280 if (*clk==0 || start < 0) return -3;
281 if (*invert != 1) *invert = 0;
282 if (amp==1) askAmp(BinStream, *size);
283 if (g_debugMode==2) prnt("DEBUG ASK: clk %d, beststart %d, amp %d", *clk, start, amp);
284
285 uint8_t initLoopMax = 255;
286 if (initLoopMax > *size) initLoopMax = *size;
287 // Detect high and lows
288 //25% clip in case highs and lows aren't clipped [marshmellow]
289 int high, low;
290 if (getHiLo(BinStream, initLoopMax, &high, &low, 75, 75) < 1)
291 return -2; //just noise
292
293 size_t errCnt = 0;
294 // if clean clipped waves detected run alternate demod
295 if (DetectCleanAskWave(BinStream, *size, high, low)) {
296 if (g_debugMode==2) prnt("DEBUG ASK: Clean Wave Detected - using clean wave demod");
297 errCnt = cleanAskRawDemod(BinStream, size, *clk, *invert, high, low);
298 if (askType) //askman
299 return manrawdecode(BinStream, size, 0);
300 else //askraw
301 return errCnt;
302 }
303 if (g_debugMode==2) prnt("DEBUG ASK: Weak Wave Detected - using weak wave demod");
304
305 int lastBit; //set first clock check - can go negative
306 size_t i, bitnum = 0; //output counter
307 uint8_t midBit = 0;
308 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
309 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
310 size_t MaxBits = 3072; //max bits to collect
311 lastBit = start - *clk;
312
313 for (i = start; i < *size; ++i) {
314 if (i-lastBit >= *clk-tol){
315 if (BinStream[i] >= high) {
316 BinStream[bitnum++] = *invert;
317 } else if (BinStream[i] <= low) {
318 BinStream[bitnum++] = *invert ^ 1;
319 } else if (i-lastBit >= *clk+tol) {
320 if (bitnum > 0) {
321 if (g_debugMode==2) prnt("DEBUG ASK: Modulation Error at: %u", i);
322 BinStream[bitnum++]=7;
323 errCnt++;
324 }
325 } else { //in tolerance - looking for peak
326 continue;
327 }
328 midBit = 0;
329 lastBit += *clk;
330 } else if (i-lastBit >= (*clk/2-tol) && !midBit && !askType){
331 if (BinStream[i] >= high) {
332 BinStream[bitnum++] = *invert;
333 } else if (BinStream[i] <= low) {
334 BinStream[bitnum++] = *invert ^ 1;
335 } else if (i-lastBit >= *clk/2+tol) {
336 BinStream[bitnum] = BinStream[bitnum-1];
337 bitnum++;
338 } else { //in tolerance - looking for peak
339 continue;
340 }
341 midBit = 1;
342 }
343 if (bitnum >= MaxBits) break;
344 }
345 *size = bitnum;
346 return errCnt;
347 }
348
349 //by marshmellow
350 //take 10 and 01 and manchester decode
351 //run through 2 times and take least errCnt
352 int manrawdecode(uint8_t * BitStream, size_t *size, uint8_t invert)
353 {
354 uint16_t bitnum=0, MaxBits = 512, errCnt = 0;
355 size_t i, ii;
356 uint16_t bestErr = 1000, bestRun = 0;
357 if (*size < 16) return -1;
358 //find correct start position [alignment]
359 for (ii=0;ii<2;++ii){
360 for (i=ii; i<*size-3; i+=2)
361 if (BitStream[i]==BitStream[i+1])
362 errCnt++;
363
364 if (bestErr>errCnt){
365 bestErr=errCnt;
366 bestRun=ii;
367 }
368 errCnt=0;
369 }
370 //decode
371 for (i=bestRun; i < *size-3; i+=2){
372 if(BitStream[i] == 1 && (BitStream[i+1] == 0)){
373 BitStream[bitnum++]=invert;
374 } else if((BitStream[i] == 0) && BitStream[i+1] == 1){
375 BitStream[bitnum++]=invert^1;
376 } else {
377 BitStream[bitnum++]=7;
378 }
379 if(bitnum>MaxBits) break;
380 }
381 *size=bitnum;
382 return bestErr;
383 }
384
385 uint32_t manchesterEncode2Bytes(uint16_t datain) {
386 uint32_t output = 0;
387 uint8_t curBit = 0;
388 for (uint8_t i=0; i<16; i++) {
389 curBit = (datain >> (15-i) & 1);
390 output |= (1<<(((15-i)*2)+curBit));
391 }
392 return output;
393 }
394
395 //by marshmellow
396 //encode binary data into binary manchester
397 int ManchesterEncode(uint8_t *BitStream, size_t size)
398 {
399 size_t modIdx=20000, i=0;
400 if (size>modIdx) return -1;
401 for (size_t idx=0; idx < size; idx++){
402 BitStream[idx+modIdx++] = BitStream[idx];
403 BitStream[idx+modIdx++] = BitStream[idx]^1;
404 }
405 for (; i<(size*2); i++){
406 BitStream[i] = BitStream[i+20000];
407 }
408 return i;
409 }
410
411 //by marshmellow
412 //take 01 or 10 = 1 and 11 or 00 = 0
413 //check for phase errors - should never have 111 or 000 should be 01001011 or 10110100 for 1010
414 //decodes biphase or if inverted it is AKA conditional dephase encoding AKA differential manchester encoding
415 int BiphaseRawDecode(uint8_t *BitStream, size_t *size, int offset, int invert)
416 {
417 uint16_t bitnum = 0;
418 uint16_t errCnt = 0;
419 size_t i = offset;
420 uint16_t MaxBits=512;
421 //if not enough samples - error
422 if (*size < 51) return -1;
423 //check for phase change faults - skip one sample if faulty
424 uint8_t offsetA = 1, offsetB = 1;
425 for (; i<48; i+=2){
426 if (BitStream[i+1]==BitStream[i+2]) offsetA=0;
427 if (BitStream[i+2]==BitStream[i+3]) offsetB=0;
428 }
429 if (!offsetA && offsetB) offset++;
430 for (i=offset; i<*size-3; i+=2){
431 //check for phase error
432 if (BitStream[i+1]==BitStream[i+2]) {
433 BitStream[bitnum++]=7;
434 errCnt++;
435 }
436 if((BitStream[i]==1 && BitStream[i+1]==0) || (BitStream[i]==0 && BitStream[i+1]==1)){
437 BitStream[bitnum++]=1^invert;
438 } else if((BitStream[i]==0 && BitStream[i+1]==0) || (BitStream[i]==1 && BitStream[i+1]==1)){
439 BitStream[bitnum++]=invert;
440 } else {
441 BitStream[bitnum++]=7;
442 errCnt++;
443 }
444 if(bitnum>MaxBits) break;
445 }
446 *size=bitnum;
447 return errCnt;
448 }
449
450 // by marshmellow
451 // demod gProxIIDemod
452 // error returns as -x
453 // success returns start position in BitStream
454 // BitStream must contain previously askrawdemod and biphasedemoded data
455 int gProxII_Demod(uint8_t BitStream[], size_t *size)
456 {
457 size_t startIdx=0;
458 uint8_t preamble[] = {1,1,1,1,1,0};
459
460 uint8_t errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, &startIdx);
461 if (errChk == 0) return -3; //preamble not found
462 if (*size != 96) return -2; //should have found 96 bits
463 //check first 6 spacer bits to verify format
464 if (!BitStream[startIdx+5] && !BitStream[startIdx+10] && !BitStream[startIdx+15] && !BitStream[startIdx+20] && !BitStream[startIdx+25] && !BitStream[startIdx+30]){
465 //confirmed proper separator bits found
466 //return start position
467 return (int) startIdx;
468 }
469 return -5; //spacer bits not found - not a valid gproxII
470 }
471
472 //translate wave to 11111100000 (1 for each short wave [higher freq] 0 for each long wave [lower freq])
473 size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow)
474 {
475 size_t last_transition = 0;
476 size_t idx = 1;
477 //uint32_t maxVal=0;
478 if (fchigh==0) fchigh=10;
479 if (fclow==0) fclow=8;
480 //set the threshold close to 0 (graph) or 128 std to avoid static
481 uint8_t threshold_value = 123;
482 size_t preLastSample = 0;
483 size_t LastSample = 0;
484 size_t currSample = 0;
485 // sync to first lo-hi transition, and threshold
486
487 // Need to threshold first sample
488 // skip 160 samples to allow antenna/samples to settle
489 if(dest[160] < threshold_value) dest[0] = 0;
490 else dest[0] = 1;
491
492 size_t numBits = 0;
493 // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
494 // or 10 (fc/10) cycles but in practice due to noise etc we may end up with anywhere
495 // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
496 // (could also be fc/5 && fc/7 for fsk1 = 4-9)
497 for(idx = 161; idx < size-20; idx++) {
498 // threshold current value
499
500 if (dest[idx] < threshold_value) dest[idx] = 0;
501 else dest[idx] = 1;
502
503 // Check for 0->1 transition
504 if (dest[idx-1] < dest[idx]) {
505 preLastSample = LastSample;
506 LastSample = currSample;
507 currSample = idx-last_transition;
508 if (currSample < (fclow-2)) { //0-5 = garbage noise (or 0-3)
509 //do nothing with extra garbage
510 } else if (currSample < (fchigh-1)) { //6-8 = 8 sample waves (or 3-6 = 5)
511 //correct previous 9 wave surrounded by 8 waves (or 6 surrounded by 5)
512 if (LastSample > (fchigh-2) && (preLastSample < (fchigh-1) || preLastSample == 0 )){
513 dest[numBits-1]=1;
514 }
515 dest[numBits++]=1;
516
517 } else if (currSample > (fchigh) && !numBits) { //12 + and first bit = unusable garbage
518 //do nothing with beginning garbage
519 } 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)
520 dest[numBits++]=1;
521 } else { //9+ = 10 sample waves (or 6+ = 7)
522 dest[numBits++]=0;
523 }
524 last_transition = idx;
525 }
526 }
527 return numBits; //Actually, it returns the number of bytes, but each byte represents a bit: 1 or 0
528 }
529
530 //translate 11111100000 to 10
531 //rfLen = clock, fchigh = larger field clock, fclow = smaller field clock
532 size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen,
533 uint8_t invert, uint8_t fchigh, uint8_t fclow)
534 {
535 uint8_t lastval=dest[0];
536 size_t idx=0;
537 size_t numBits=0;
538 uint32_t n=1;
539 for( idx=1; idx < size; idx++) {
540 n++;
541 if (dest[idx]==lastval) continue; //skip until we hit a transition
542
543 //find out how many bits (n) we collected
544 //if lastval was 1, we have a 1->0 crossing
545 if (dest[idx-1]==1) {
546 n = (n * fclow + rfLen/2) / rfLen;
547 } else {// 0->1 crossing
548 n = (n * fchigh + rfLen/2) / rfLen;
549 }
550 if (n == 0) n = 1;
551
552 //add to our destination the bits we collected
553 memset(dest+numBits, dest[idx-1]^invert , n);
554 numBits += n;
555 n=0;
556 lastval=dest[idx];
557 }//end for
558 // if valid extra bits at the end were all the same frequency - add them in
559 if (n > rfLen/fchigh) {
560 if (dest[idx-2]==1) {
561 n = (n * fclow + rfLen/2) / rfLen;
562 } else {
563 n = (n * fchigh + rfLen/2) / rfLen;
564 }
565 memset(dest+numBits, dest[idx-1]^invert , n);
566 numBits += n;
567 }
568 return numBits;
569 }
570
571 //by marshmellow (from holiman's base)
572 // full fsk demod from GraphBuffer wave to decoded 1s and 0s (no mandemod)
573 int fskdemod(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow)
574 {
575 // FSK demodulator
576 size = fsk_wave_demod(dest, size, fchigh, fclow);
577 size = aggregate_bits(dest, size, rfLen, invert, fchigh, fclow);
578 return size;
579 }
580
581 // loop to get raw HID waveform then FSK demodulate the TAG ID from it
582 int HIDdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
583 {
584 if (justNoise(dest, *size)) return -1;
585
586 size_t numStart=0, size2=*size, startIdx=0;
587 // FSK demodulator
588 *size = fskdemod(dest, size2,50,1,10,8); //fsk2a
589 if (*size < 96*2) return -2;
590 // 00011101 bit pattern represent start of frame, 01 pattern represents a 0 and 10 represents a 1
591 uint8_t preamble[] = {0,0,0,1,1,1,0,1};
592 // find bitstring in array
593 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
594 if (errChk == 0) return -3; //preamble not found
595
596 numStart = startIdx + sizeof(preamble);
597 // final loop, go over previously decoded FSK data and manchester decode into usable tag ID
598 for (size_t idx = numStart; (idx-numStart) < *size - sizeof(preamble); idx+=2){
599 if (dest[idx] == dest[idx+1]){
600 return -4; //not manchester data
601 }
602 *hi2 = (*hi2<<1)|(*hi>>31);
603 *hi = (*hi<<1)|(*lo>>31);
604 //Then, shift in a 0 or one into low
605 if (dest[idx] && !dest[idx+1]) // 1 0
606 *lo=(*lo<<1)|1;
607 else // 0 1
608 *lo=(*lo<<1)|0;
609 }
610 return (int)startIdx;
611 }
612
613 // loop to get raw paradox waveform then FSK demodulate the TAG ID from it
614 int ParadoxdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
615 {
616 if (justNoise(dest, *size)) return -1;
617
618 size_t numStart=0, size2=*size, startIdx=0;
619 // FSK demodulator
620 *size = fskdemod(dest, size2,50,1,10,8); //fsk2a
621 if (*size < 96) return -2;
622
623 // 00001111 bit pattern represent start of frame, 01 pattern represents a 0 and 10 represents a 1
624 uint8_t preamble[] = {0,0,0,0,1,1,1,1};
625
626 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
627 if (errChk == 0) return -3; //preamble not found
628
629 numStart = startIdx + sizeof(preamble);
630 // final loop, go over previously decoded FSK data and manchester decode into usable tag ID
631 for (size_t idx = numStart; (idx-numStart) < *size - sizeof(preamble); idx+=2){
632 if (dest[idx] == dest[idx+1])
633 return -4; //not manchester data
634 *hi2 = (*hi2<<1)|(*hi>>31);
635 *hi = (*hi<<1)|(*lo>>31);
636 //Then, shift in a 0 or one into low
637 if (dest[idx] && !dest[idx+1]) // 1 0
638 *lo=(*lo<<1)|1;
639 else // 0 1
640 *lo=(*lo<<1)|0;
641 }
642 return (int)startIdx;
643 }
644
645 int IOdemodFSK(uint8_t *dest, size_t size)
646 {
647 if (justNoise(dest, size)) return -1;
648 //make sure buffer has data
649 if (size < 66*64) return -2;
650 // FSK demodulator
651 size = fskdemod(dest, size, 64, 1, 10, 8); // FSK2a RF/64
652 if (size < 65) return -3; //did we get a good demod?
653 //Index map
654 //0 10 20 30 40 50 60
655 //| | | | | | |
656 //01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
657 //-----------------------------------------------------------------------------
658 //00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
659 //
660 //XSF(version)facility:codeone+codetwo
661 //Handle the data
662 size_t startIdx = 0;
663 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,1};
664 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), &size, &startIdx);
665 if (errChk == 0) return -4; //preamble not found
666
667 if (!dest[startIdx+8] && dest[startIdx+17]==1 && dest[startIdx+26]==1 && dest[startIdx+35]==1 && dest[startIdx+44]==1 && dest[startIdx+53]==1){
668 //confirmed proper separator bits found
669 //return start position
670 return (int) startIdx;
671 }
672 return -5;
673 }
674
675 // by marshmellow
676 // find viking preamble 0xF200 in already demoded data
677 int VikingDemod_AM(uint8_t *dest, size_t *size) {
678 //make sure buffer has data
679 if (*size < 64*2) return -2;
680
681 size_t startIdx = 0;
682 uint8_t preamble[] = {1,1,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
683 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
684 if (errChk == 0) return -4; //preamble not found
685 uint32_t checkCalc = bytebits_to_byte(dest+startIdx,8) ^ bytebits_to_byte(dest+startIdx+8,8) ^ bytebits_to_byte(dest+startIdx+16,8)
686 ^ bytebits_to_byte(dest+startIdx+24,8) ^ bytebits_to_byte(dest+startIdx+32,8) ^ bytebits_to_byte(dest+startIdx+40,8)
687 ^ bytebits_to_byte(dest+startIdx+48,8) ^ bytebits_to_byte(dest+startIdx+56,8);
688 if ( checkCalc != 0xA8 ) return -5;
689 if (*size != 64) return -6;
690 //return start position
691 return (int) startIdx;
692 }
693
694 // find presco preamble 0x10D in already demoded data
695 int PrescoDemod(uint8_t *dest, size_t *size) {
696 //make sure buffer has data
697 if (*size < 64*2) return -2;
698
699 size_t startIdx = 0;
700 uint8_t preamble[] = {1,0,0,0,0,1,1,0,1,0,0,0,0,0,0,0,0,0,0,0};
701 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
702 if (errChk == 0) return -4; //preamble not found
703 //return start position
704 return (int) startIdx;
705 }
706
707 // Ask/Biphase Demod then try to locate an ISO 11784/85 ID
708 // BitStream must contain previously askrawdemod and biphasedemoded data
709 int FDXBdemodBI(uint8_t *dest, size_t *size)
710 {
711 //make sure buffer has enough data
712 if (*size < 128) return -1;
713
714 size_t startIdx = 0;
715 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,1};
716
717 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
718 if (errChk == 0) return -2; //preamble not found
719 return (int)startIdx;
720 }
721
722 // by marshmellow
723 // FSK Demod then try to locate an AWID ID
724 int AWIDdemodFSK(uint8_t *dest, size_t *size)
725 {
726 //make sure buffer has enough data
727 if (*size < 96*50) return -1;
728
729 if (justNoise(dest, *size)) return -2;
730
731 // FSK demodulator
732 *size = fskdemod(dest, *size, 50, 1, 10, 8); // fsk2a RF/50
733 if (*size < 96) return -3; //did we get a good demod?
734
735 uint8_t preamble[] = {0,0,0,0,0,0,0,1};
736 size_t startIdx = 0;
737 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
738 if (errChk == 0) return -4; //preamble not found
739 if (*size != 96) return -5;
740 return (int)startIdx;
741 }
742
743 // by marshmellow
744 // FSK Demod then try to locate a Farpointe Data (pyramid) ID
745 int PyramiddemodFSK(uint8_t *dest, size_t *size)
746 {
747 //make sure buffer has data
748 if (*size < 128*50) return -5;
749
750 //test samples are not just noise
751 if (justNoise(dest, *size)) return -1;
752
753 // FSK demodulator
754 *size = fskdemod(dest, *size, 50, 1, 10, 8); // fsk2a RF/50
755 if (*size < 128) return -2; //did we get a good demod?
756
757 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
758 size_t startIdx = 0;
759 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
760 if (errChk == 0) return -4; //preamble not found
761 if (*size != 128) return -3;
762 return (int)startIdx;
763 }
764
765 // by marshmellow
766 // to detect a wave that has heavily clipped (clean) samples
767 uint8_t DetectCleanAskWave(uint8_t dest[], size_t size, uint8_t high, uint8_t low)
768 {
769 bool allArePeaks = true;
770 uint16_t cntPeaks=0;
771 size_t loopEnd = 512+160;
772 if (loopEnd > size) loopEnd = size;
773 for (size_t i=160; i<loopEnd; i++){
774 if (dest[i]>low && dest[i]<high)
775 allArePeaks = false;
776 else
777 cntPeaks++;
778 }
779 if (!allArePeaks){
780 if (cntPeaks > 300) return true;
781 }
782 return allArePeaks;
783 }
784 // by marshmellow
785 // to help detect clocks on heavily clipped samples
786 // based on count of low to low
787 int DetectStrongAskClock(uint8_t dest[], size_t size, uint8_t high, uint8_t low)
788 {
789 uint8_t fndClk[] = {8,16,32,40,50,64,128};
790 size_t startwave;
791 size_t i = 100;
792 size_t minClk = 255;
793 // get to first full low to prime loop and skip incomplete first pulse
794 while ((dest[i] < high) && (i < size))
795 ++i;
796 while ((dest[i] > low) && (i < size))
797 ++i;
798
799 // loop through all samples
800 while (i < size) {
801 // measure from low to low
802 while ((dest[i] > low) && (i < size))
803 ++i;
804 startwave= i;
805 while ((dest[i] < high) && (i < size))
806 ++i;
807 while ((dest[i] > low) && (i < size))
808 ++i;
809 //get minimum measured distance
810 if (i-startwave < minClk && i < size)
811 minClk = i - startwave;
812 }
813 // set clock
814 if (g_debugMode==2) prnt("DEBUG ASK: detectstrongASKclk smallest wave: %d",minClk);
815 for (uint8_t clkCnt = 0; clkCnt<7; clkCnt++) {
816 if (minClk >= fndClk[clkCnt]-(fndClk[clkCnt]/8) && minClk <= fndClk[clkCnt]+1)
817 return fndClk[clkCnt];
818 }
819 return 0;
820 }
821
822 // by marshmellow
823 // not perfect especially with lower clocks or VERY good antennas (heavy wave clipping)
824 // maybe somehow adjust peak trimming value based on samples to fix?
825 // return start index of best starting position for that clock and return clock (by reference)
826 int DetectASKClock(uint8_t dest[], size_t size, int *clock, int maxErr)
827 {
828 size_t i=1;
829 uint8_t clk[] = {255,8,16,32,40,50,64,100,128,255};
830 uint8_t clkEnd = 9;
831 uint8_t loopCnt = 255; //don't need to loop through entire array...
832 if (size <= loopCnt+60) return -1; //not enough samples
833 size -= 60; //sometimes there is a strange end wave - filter out this....
834 //if we already have a valid clock
835 uint8_t clockFnd=0;
836 for (;i<clkEnd;++i)
837 if (clk[i] == *clock) clockFnd = i;
838 //clock found but continue to find best startpos
839
840 //get high and low peak
841 int peak, low;
842 if (getHiLo(dest, loopCnt, &peak, &low, 75, 75) < 1) return -1;
843
844 //test for large clean peaks
845 if (!clockFnd){
846 if (DetectCleanAskWave(dest, size, peak, low)==1){
847 int ans = DetectStrongAskClock(dest, size, peak, low);
848 if (g_debugMode==2) prnt("DEBUG ASK: detectaskclk Clean Ask Wave Detected: clk %d",ans);
849 for (i=clkEnd-1; i>0; i--){
850 if (clk[i] == ans) {
851 *clock = ans;
852 //clockFnd = i;
853 return 0; // for strong waves i don't use the 'best start position' yet...
854 //break; //clock found but continue to find best startpos [not yet]
855 }
856 }
857 }
858 }
859 uint8_t ii;
860 uint8_t clkCnt, tol = 0;
861 uint16_t bestErr[]={1000,1000,1000,1000,1000,1000,1000,1000,1000};
862 uint8_t bestStart[]={0,0,0,0,0,0,0,0,0};
863 size_t errCnt = 0;
864 size_t arrLoc, loopEnd;
865
866 if (clockFnd>0) {
867 clkCnt = clockFnd;
868 clkEnd = clockFnd+1;
869 }
870 else clkCnt=1;
871
872 //test each valid clock from smallest to greatest to see which lines up
873 for(; clkCnt < clkEnd; clkCnt++){
874 if (clk[clkCnt] <= 32){
875 tol=1;
876 }else{
877 tol=0;
878 }
879 //if no errors allowed - keep start within the first clock
880 if (!maxErr && size > clk[clkCnt]*2 + tol && clk[clkCnt]<128) loopCnt=clk[clkCnt]*2;
881 bestErr[clkCnt]=1000;
882 //try lining up the peaks by moving starting point (try first few clocks)
883 for (ii=0; ii < loopCnt; ii++){
884 if (dest[ii] < peak && dest[ii] > low) continue;
885
886 errCnt=0;
887 // now that we have the first one lined up test rest of wave array
888 loopEnd = ((size-ii-tol) / clk[clkCnt]) - 1;
889 for (i=0; i < loopEnd; ++i){
890 arrLoc = ii + (i * clk[clkCnt]);
891 if (dest[arrLoc] >= peak || dest[arrLoc] <= low){
892 }else if (dest[arrLoc-tol] >= peak || dest[arrLoc-tol] <= low){
893 }else if (dest[arrLoc+tol] >= peak || dest[arrLoc+tol] <= low){
894 }else{ //error no peak detected
895 errCnt++;
896 }
897 }
898 //if we found no errors then we can stop here and a low clock (common clocks)
899 // this is correct one - return this clock
900 if (g_debugMode == 2) prnt("DEBUG ASK: clk %d, err %d, startpos %d, endpos %d",clk[clkCnt],errCnt,ii,i);
901 if(errCnt==0 && clkCnt<7) {
902 if (!clockFnd) *clock = clk[clkCnt];
903 return ii;
904 }
905 //if we found errors see if it is lowest so far and save it as best run
906 if(errCnt<bestErr[clkCnt]){
907 bestErr[clkCnt]=errCnt;
908 bestStart[clkCnt]=ii;
909 }
910 }
911 }
912 uint8_t iii;
913 uint8_t best=0;
914 for (iii=1; iii<clkEnd; ++iii){
915 if (bestErr[iii] < bestErr[best]){
916 if (bestErr[iii] == 0) bestErr[iii]=1;
917 // current best bit to error ratio vs new bit to error ratio
918 if ( (size/clk[best])/bestErr[best] < (size/clk[iii])/bestErr[iii] ){
919 best = iii;
920 }
921 }
922 if (g_debugMode == 2) prnt("DEBUG ASK: clk %d, # Errors %d, Current Best Clk %d, bestStart %d",clk[iii],bestErr[iii],clk[best],bestStart[best]);
923 }
924 if (!clockFnd) *clock = clk[best];
925 return bestStart[best];
926 }
927
928 //by marshmellow
929 //detect psk clock by reading each phase shift
930 // a phase shift is determined by measuring the sample length of each wave
931 int DetectPSKClock(uint8_t dest[], size_t size, int clock)
932 {
933 uint8_t clk[]={255,16,32,40,50,64,100,128,255}; //255 is not a valid clock
934 uint16_t loopCnt = 4096; //don't need to loop through entire array...
935 if (size == 0) return 0;
936 if (size<loopCnt) loopCnt = size-20;
937
938 //if we already have a valid clock quit
939 size_t i=1;
940 for (; i < 8; ++i)
941 if (clk[i] == clock) return clock;
942
943 size_t waveStart=0, waveEnd=0, firstFullWave=0, lastClkBit=0;
944 uint8_t clkCnt, fc=0, fullWaveLen=0, tol=1;
945 uint16_t peakcnt=0, errCnt=0, waveLenCnt=0;
946 uint16_t bestErr[]={1000,1000,1000,1000,1000,1000,1000,1000,1000};
947 uint16_t peaksdet[]={0,0,0,0,0,0,0,0,0};
948 fc = countFC(dest, size, 0);
949 if (fc!=2 && fc!=4 && fc!=8) return -1;
950 if (g_debugMode==2) prnt("DEBUG PSK: FC: %d",fc);
951
952 //find first full wave
953 for (i=160; i<loopCnt; i++){
954 if (dest[i] < dest[i+1] && dest[i+1] >= dest[i+2]){
955 if (waveStart == 0) {
956 waveStart = i+1;
957 //prnt("DEBUG: waveStart: %d",waveStart);
958 } else {
959 waveEnd = i+1;
960 //prnt("DEBUG: waveEnd: %d",waveEnd);
961 waveLenCnt = waveEnd-waveStart;
962 if (waveLenCnt > fc){
963 firstFullWave = waveStart;
964 fullWaveLen=waveLenCnt;
965 break;
966 }
967 waveStart=0;
968 }
969 }
970 }
971 if (g_debugMode ==2) prnt("DEBUG PSK: firstFullWave: %d, waveLen: %d",firstFullWave,fullWaveLen);
972
973 //test each valid clock from greatest to smallest to see which lines up
974 for(clkCnt=7; clkCnt >= 1 ; clkCnt--){
975 lastClkBit = firstFullWave; //set end of wave as clock align
976 waveStart = 0;
977 errCnt=0;
978 peakcnt=0;
979 if (g_debugMode == 2) prnt("DEBUG PSK: clk: %d, lastClkBit: %d",clk[clkCnt],lastClkBit);
980
981 for (i = firstFullWave+fullWaveLen-1; i < loopCnt-2; i++){
982 //top edge of wave = start of new wave
983 if (dest[i] < dest[i+1] && dest[i+1] >= dest[i+2]){
984 if (waveStart == 0) {
985 waveStart = i+1;
986 waveLenCnt=0;
987 } else { //waveEnd
988 waveEnd = i+1;
989 waveLenCnt = waveEnd-waveStart;
990 if (waveLenCnt > fc){
991 //if this wave is a phase shift
992 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);
993 if (i+1 >= lastClkBit + clk[clkCnt] - tol){ //should be a clock bit
994 peakcnt++;
995 lastClkBit+=clk[clkCnt];
996 } else if (i<lastClkBit+8){
997 //noise after a phase shift - ignore
998 } else { //phase shift before supposed to based on clock
999 errCnt++;
1000 }
1001 } else if (i+1 > lastClkBit + clk[clkCnt] + tol + fc){
1002 lastClkBit+=clk[clkCnt]; //no phase shift but clock bit
1003 }
1004 waveStart=i+1;
1005 }
1006 }
1007 }
1008 if (errCnt == 0){
1009 return clk[clkCnt];
1010 }
1011 if (errCnt <= bestErr[clkCnt]) bestErr[clkCnt]=errCnt;
1012 if (peakcnt > peaksdet[clkCnt]) peaksdet[clkCnt]=peakcnt;
1013 }
1014 //all tested with errors
1015 //return the highest clk with the most peaks found
1016 uint8_t best=7;
1017 for (i=7; i>=1; i--){
1018 if (peaksdet[i] > peaksdet[best]) {
1019 best = i;
1020 }
1021 if (g_debugMode == 2) prnt("DEBUG PSK: Clk: %d, peaks: %d, errs: %d, bestClk: %d",clk[i],peaksdet[i],bestErr[i],clk[best]);
1022 }
1023 return clk[best];
1024 }
1025
1026 int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low){
1027 //find shortest transition from high to low
1028 size_t i = 0;
1029 size_t transition1 = 0;
1030 int lowestTransition = 255;
1031 bool lastWasHigh = false;
1032
1033 //find first valid beginning of a high or low wave
1034 while ((dest[i] >= peak || dest[i] <= low) && (i < size))
1035 ++i;
1036 while ((dest[i] < peak && dest[i] > low) && (i < size))
1037 ++i;
1038 lastWasHigh = (dest[i] >= peak);
1039
1040 if (i==size) return 0;
1041 transition1 = i;
1042
1043 for (;i < size; i++) {
1044 if ((dest[i] >= peak && !lastWasHigh) || (dest[i] <= low && lastWasHigh)) {
1045 lastWasHigh = (dest[i] >= peak);
1046 if (i-transition1 < lowestTransition) lowestTransition = i-transition1;
1047 transition1 = i;
1048 }
1049 }
1050 if (lowestTransition == 255) lowestTransition = 0;
1051 if (g_debugMode==2) prnt("DEBUG NRZ: detectstrongNRZclk smallest wave: %d",lowestTransition);
1052 return lowestTransition;
1053 }
1054
1055 //by marshmellow
1056 //detect nrz clock by reading #peaks vs no peaks(or errors)
1057 int DetectNRZClock(uint8_t dest[], size_t size, int clock)
1058 {
1059 size_t i=0;
1060 uint8_t clk[]={8,16,32,40,50,64,100,128,255};
1061 size_t loopCnt = 4096; //don't need to loop through entire array...
1062 if (size == 0) return 0;
1063 if (size<loopCnt) loopCnt = size-20;
1064 //if we already have a valid clock quit
1065 for (; i < 8; ++i)
1066 if (clk[i] == clock) return clock;
1067
1068 //get high and low peak
1069 int peak, low;
1070 if (getHiLo(dest, loopCnt, &peak, &low, 75, 75) < 1) return 0;
1071
1072 int lowestTransition = DetectStrongNRZClk(dest, size-20, peak, low);
1073 size_t ii;
1074 uint8_t clkCnt;
1075 uint8_t tol = 0;
1076 uint16_t smplCnt = 0;
1077 int16_t peakcnt = 0;
1078 int16_t peaksdet[] = {0,0,0,0,0,0,0,0};
1079 uint16_t maxPeak = 255;
1080 bool firstpeak = false;
1081 //test for large clipped waves
1082 for (i=0; i<loopCnt; i++){
1083 if (dest[i] >= peak || dest[i] <= low){
1084 if (!firstpeak) continue;
1085 smplCnt++;
1086 } else {
1087 firstpeak=true;
1088 if (smplCnt > 6 ){
1089 if (maxPeak > smplCnt){
1090 maxPeak = smplCnt;
1091 //prnt("maxPk: %d",maxPeak);
1092 }
1093 peakcnt++;
1094 //prnt("maxPk: %d, smplCnt: %d, peakcnt: %d",maxPeak,smplCnt,peakcnt);
1095 smplCnt=0;
1096 }
1097 }
1098 }
1099 bool errBitHigh = 0;
1100 bool bitHigh = 0;
1101 uint8_t ignoreCnt = 0;
1102 uint8_t ignoreWindow = 4;
1103 bool lastPeakHigh = 0;
1104 int lastBit = 0;
1105 peakcnt=0;
1106 //test each valid clock from smallest to greatest to see which lines up
1107 for(clkCnt=0; clkCnt < 8; ++clkCnt){
1108 //ignore clocks smaller than smallest peak
1109 if (clk[clkCnt] < maxPeak - (clk[clkCnt]/4)) continue;
1110 //try lining up the peaks by moving starting point (try first 256)
1111 for (ii=20; ii < loopCnt; ++ii){
1112 if ((dest[ii] >= peak) || (dest[ii] <= low)){
1113 peakcnt = 0;
1114 bitHigh = false;
1115 ignoreCnt = 0;
1116 lastBit = ii-clk[clkCnt];
1117 //loop through to see if this start location works
1118 for (i = ii; i < size-20; ++i) {
1119 //if we are at a clock bit
1120 if ((i >= lastBit + clk[clkCnt] - tol) && (i <= lastBit + clk[clkCnt] + tol)) {
1121 //test high/low
1122 if (dest[i] >= peak || dest[i] <= low) {
1123 //if same peak don't count it
1124 if ((dest[i] >= peak && !lastPeakHigh) || (dest[i] <= low && lastPeakHigh)) {
1125 peakcnt++;
1126 }
1127 lastPeakHigh = (dest[i] >= peak);
1128 bitHigh = true;
1129 errBitHigh = false;
1130 ignoreCnt = ignoreWindow;
1131 lastBit += clk[clkCnt];
1132 } else if (i == lastBit + clk[clkCnt] + tol) {
1133 lastBit += clk[clkCnt];
1134 }
1135 //else if not a clock bit and no peaks
1136 } else if (dest[i] < peak && dest[i] > low){
1137 if (ignoreCnt==0){
1138 bitHigh=false;
1139 if (errBitHigh==true) peakcnt--;
1140 errBitHigh=false;
1141 } else {
1142 ignoreCnt--;
1143 }
1144 // else if not a clock bit but we have a peak
1145 } else if ((dest[i]>=peak || dest[i]<=low) && (!bitHigh)) {
1146 //error bar found no clock...
1147 errBitHigh=true;
1148 }
1149 }
1150 if(peakcnt>peaksdet[clkCnt]) {
1151 peaksdet[clkCnt]=peakcnt;
1152 }
1153 }
1154 }
1155 }
1156 int iii=7;
1157 uint8_t best=0;
1158 for (iii=7; iii > 0; iii--){
1159 if ((peaksdet[iii] >= (peaksdet[best]-1)) && (peaksdet[iii] <= peaksdet[best]+1) && lowestTransition) {
1160 if (clk[iii] > (lowestTransition - (clk[iii]/8)) && clk[iii] < (lowestTransition + (clk[iii]/8))) {
1161 best = iii;
1162 }
1163 } else if (peaksdet[iii] > peaksdet[best]){
1164 best = iii;
1165 }
1166 if (g_debugMode==2) prnt("DEBUG NRZ: Clk: %d, peaks: %d, maxPeak: %d, bestClk: %d, lowestTrs: %d",clk[iii],peaksdet[iii],maxPeak, clk[best], lowestTransition);
1167 }
1168
1169 return clk[best];
1170 }
1171
1172 // by marshmellow
1173 // convert psk1 demod to psk2 demod
1174 // only transition waves are 1s
1175 void psk1TOpsk2(uint8_t *BitStream, size_t size)
1176 {
1177 size_t i=1;
1178 uint8_t lastBit=BitStream[0];
1179 for (; i<size; i++){
1180 if (BitStream[i]==7){
1181 //ignore errors
1182 } else if (lastBit!=BitStream[i]){
1183 lastBit=BitStream[i];
1184 BitStream[i]=1;
1185 } else {
1186 BitStream[i]=0;
1187 }
1188 }
1189 return;
1190 }
1191
1192 // by marshmellow
1193 // convert psk2 demod to psk1 demod
1194 // from only transition waves are 1s to phase shifts change bit
1195 void psk2TOpsk1(uint8_t *BitStream, size_t size)
1196 {
1197 uint8_t phase=0;
1198 for (size_t i=0; i<size; i++){
1199 if (BitStream[i]==1){
1200 phase ^=1;
1201 }
1202 BitStream[i]=phase;
1203 }
1204 return;
1205 }
1206
1207 // redesigned by marshmellow adjusted from existing decode functions
1208 // indala id decoding - only tested on 26 bit tags, but attempted to make it work for more
1209 int indala26decode(uint8_t *bitStream, size_t *size, uint8_t *invert)
1210 {
1211 //26 bit 40134 format (don't know other formats)
1212 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
1213 uint8_t preamble_i[] = {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0};
1214 size_t startidx = 0;
1215 if (!preambleSearch(bitStream, preamble, sizeof(preamble), size, &startidx)){
1216 // if didn't find preamble try again inverting
1217 if (!preambleSearch(bitStream, preamble_i, sizeof(preamble_i), size, &startidx)) return -1;
1218 *invert ^= 1;
1219 }
1220 if (*size != 64 && *size != 224) return -2;
1221 if (*invert==1)
1222 for (size_t i = startidx; i < *size; i++)
1223 bitStream[i] ^= 1;
1224
1225 return (int) startidx;
1226 }
1227
1228 // by marshmellow - demodulate NRZ wave - requires a read with strong signal
1229 // peaks invert bit (high=1 low=0) each clock cycle = 1 bit determined by last peak
1230 int nrzRawDemod(uint8_t *dest, size_t *size, int *clk, int *invert){
1231 if (justNoise(dest, *size)) return -1;
1232 *clk = DetectNRZClock(dest, *size, *clk);
1233 if (*clk==0) return -2;
1234 size_t i, gLen = 4096;
1235 if (gLen>*size) gLen = *size-20;
1236 int high, low;
1237 if (getHiLo(dest, gLen, &high, &low, 75, 75) < 1) return -3; //25% fuzz on high 25% fuzz on low
1238
1239 uint8_t bit=0;
1240 //convert wave samples to 1's and 0's
1241 for(i=20; i < *size-20; i++){
1242 if (dest[i] >= high) bit = 1;
1243 if (dest[i] <= low) bit = 0;
1244 dest[i] = bit;
1245 }
1246 //now demod based on clock (rf/32 = 32 1's for one 1 bit, 32 0's for one 0 bit)
1247 size_t lastBit = 0;
1248 size_t numBits = 0;
1249 for(i=21; i < *size-20; i++) {
1250 //if transition detected or large number of same bits - store the passed bits
1251 if (dest[i] != dest[i-1] || (i-lastBit) == (10 * *clk)) {
1252 memset(dest+numBits, dest[i-1] ^ *invert, (i - lastBit + (*clk/4)) / *clk);
1253 numBits += (i - lastBit + (*clk/4)) / *clk;
1254 lastBit = i-1;
1255 }
1256 }
1257 *size = numBits;
1258 return 0;
1259 }
1260
1261 //by marshmellow
1262 //detects the bit clock for FSK given the high and low Field Clocks
1263 uint8_t detectFSKClk(uint8_t *BitStream, size_t size, uint8_t fcHigh, uint8_t fcLow)
1264 {
1265 uint8_t clk[] = {8,16,32,40,50,64,100,128,0};
1266 uint16_t rfLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1267 uint8_t rfCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1268 uint8_t rfLensFnd = 0;
1269 uint8_t lastFCcnt = 0;
1270 uint16_t fcCounter = 0;
1271 uint16_t rfCounter = 0;
1272 uint8_t firstBitFnd = 0;
1273 size_t i;
1274 if (size == 0) return 0;
1275
1276 uint8_t fcTol = ((fcHigh*100 - fcLow*100)/2 + 50)/100; //(uint8_t)(0.5+(float)(fcHigh-fcLow)/2);
1277 rfLensFnd=0;
1278 fcCounter=0;
1279 rfCounter=0;
1280 firstBitFnd=0;
1281 //PrintAndLog("DEBUG: fcTol: %d",fcTol);
1282 // prime i to first peak / up transition
1283 for (i = 160; i < size-20; i++)
1284 if (BitStream[i] > BitStream[i-1] && BitStream[i]>=BitStream[i+1])
1285 break;
1286
1287 for (; i < size-20; i++){
1288 fcCounter++;
1289 rfCounter++;
1290
1291 if (BitStream[i] <= BitStream[i-1] || BitStream[i] < BitStream[i+1])
1292 continue;
1293 // else new peak
1294 // if we got less than the small fc + tolerance then set it to the small fc
1295 if (fcCounter < fcLow+fcTol)
1296 fcCounter = fcLow;
1297 else //set it to the large fc
1298 fcCounter = fcHigh;
1299
1300 //look for bit clock (rf/xx)
1301 if ((fcCounter < lastFCcnt || fcCounter > lastFCcnt)){
1302 //not the same size as the last wave - start of new bit sequence
1303 if (firstBitFnd > 1){ //skip first wave change - probably not a complete bit
1304 for (int ii=0; ii<15; ii++){
1305 if (rfLens[ii] >= (rfCounter-4) && rfLens[ii] <= (rfCounter+4)){
1306 rfCnts[ii]++;
1307 rfCounter = 0;
1308 break;
1309 }
1310 }
1311 if (rfCounter > 0 && rfLensFnd < 15){
1312 //PrintAndLog("DEBUG: rfCntr %d, fcCntr %d",rfCounter,fcCounter);
1313 rfCnts[rfLensFnd]++;
1314 rfLens[rfLensFnd++] = rfCounter;
1315 }
1316 } else {
1317 firstBitFnd++;
1318 }
1319 rfCounter=0;
1320 lastFCcnt=fcCounter;
1321 }
1322 fcCounter=0;
1323 }
1324 uint8_t rfHighest=15, rfHighest2=15, rfHighest3=15;
1325
1326 for (i=0; i<15; i++){
1327 //get highest 2 RF values (might need to get more values to compare or compare all?)
1328 if (rfCnts[i]>rfCnts[rfHighest]){
1329 rfHighest3=rfHighest2;
1330 rfHighest2=rfHighest;
1331 rfHighest=i;
1332 } else if(rfCnts[i]>rfCnts[rfHighest2]){
1333 rfHighest3=rfHighest2;
1334 rfHighest2=i;
1335 } else if(rfCnts[i]>rfCnts[rfHighest3]){
1336 rfHighest3=i;
1337 }
1338 if (g_debugMode==2) prnt("DEBUG FSK: RF %d, cnts %d",rfLens[i], rfCnts[i]);
1339 }
1340 // set allowed clock remainder tolerance to be 1 large field clock length+1
1341 // we could have mistakenly made a 9 a 10 instead of an 8 or visa versa so rfLens could be 1 FC off
1342 uint8_t tol1 = fcHigh+1;
1343
1344 if (g_debugMode==2) prnt("DEBUG FSK: most counted rf values: 1 %d, 2 %d, 3 %d",rfLens[rfHighest],rfLens[rfHighest2],rfLens[rfHighest3]);
1345
1346 // loop to find the highest clock that has a remainder less than the tolerance
1347 // compare samples counted divided by
1348 // test 128 down to 32 (shouldn't be possible to have fc/10 & fc/8 and rf/16 or less)
1349 int ii=7;
1350 for (; ii>=2; ii--){
1351 if (rfLens[rfHighest] % clk[ii] < tol1 || rfLens[rfHighest] % clk[ii] > clk[ii]-tol1){
1352 if (rfLens[rfHighest2] % clk[ii] < tol1 || rfLens[rfHighest2] % clk[ii] > clk[ii]-tol1){
1353 if (rfLens[rfHighest3] % clk[ii] < tol1 || rfLens[rfHighest3] % clk[ii] > clk[ii]-tol1){
1354 if (g_debugMode==2) prnt("DEBUG FSK: clk %d divides into the 3 most rf values within tolerance",clk[ii]);
1355 break;
1356 }
1357 }
1358 }
1359 }
1360
1361 if (ii<0) return 0; // oops we went too far
1362
1363 return clk[ii];
1364 }
1365
1366 //by marshmellow
1367 //countFC is to detect the field clock lengths.
1368 //counts and returns the 2 most common wave lengths
1369 //mainly used for FSK field clock detection
1370 uint16_t countFC(uint8_t *BitStream, size_t size, uint8_t fskAdj)
1371 {
1372 uint8_t fcLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1373 uint16_t fcCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1374 uint8_t fcLensFnd = 0;
1375 uint8_t lastFCcnt=0;
1376 uint8_t fcCounter = 0;
1377 size_t i;
1378 if (size == 0) return 0;
1379
1380 // prime i to first up transition
1381 for (i = 160; i < size-20; i++)
1382 if (BitStream[i] > BitStream[i-1] && BitStream[i] >= BitStream[i+1])
1383 break;
1384
1385 for (; i < size-20; i++){
1386 if (BitStream[i] > BitStream[i-1] && BitStream[i] >= BitStream[i+1]){
1387 // new up transition
1388 fcCounter++;
1389 if (fskAdj){
1390 //if we had 5 and now have 9 then go back to 8 (for when we get a fc 9 instead of an 8)
1391 if (lastFCcnt==5 && fcCounter==9) fcCounter--;
1392 //if fc=9 or 4 add one (for when we get a fc 9 instead of 10 or a 4 instead of a 5)
1393 if ((fcCounter==9) || fcCounter==4) fcCounter++;
1394 // save last field clock count (fc/xx)
1395 lastFCcnt = fcCounter;
1396 }
1397 // find which fcLens to save it to:
1398 for (int ii=0; ii<15; ii++){
1399 if (fcLens[ii]==fcCounter){
1400 fcCnts[ii]++;
1401 fcCounter=0;
1402 break;
1403 }
1404 }
1405 if (fcCounter>0 && fcLensFnd<15){
1406 //add new fc length
1407 fcCnts[fcLensFnd]++;
1408 fcLens[fcLensFnd++]=fcCounter;
1409 }
1410 fcCounter=0;
1411 } else {
1412 // count sample
1413 fcCounter++;
1414 }
1415 }
1416
1417 uint8_t best1=14, best2=14, best3=14;
1418 uint16_t maxCnt1=0;
1419 // go through fclens and find which ones are bigest 2
1420 for (i=0; i<15; i++){
1421 // get the 3 best FC values
1422 if (fcCnts[i]>maxCnt1) {
1423 best3=best2;
1424 best2=best1;
1425 maxCnt1=fcCnts[i];
1426 best1=i;
1427 } else if(fcCnts[i]>fcCnts[best2]){
1428 best3=best2;
1429 best2=i;
1430 } else if(fcCnts[i]>fcCnts[best3]){
1431 best3=i;
1432 }
1433 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]);
1434 }
1435 if (fcLens[best1]==0) return 0;
1436 uint8_t fcH=0, fcL=0;
1437 if (fcLens[best1]>fcLens[best2]){
1438 fcH=fcLens[best1];
1439 fcL=fcLens[best2];
1440 } else{
1441 fcH=fcLens[best2];
1442 fcL=fcLens[best1];
1443 }
1444 if ((size-180)/fcH/3 > fcCnts[best1]+fcCnts[best2]) {
1445 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]);
1446 return 0; //lots of waves not psk or fsk
1447 }
1448 // TODO: take top 3 answers and compare to known Field clocks to get top 2
1449
1450 uint16_t fcs = (((uint16_t)fcH)<<8) | fcL;
1451 if (fskAdj) return fcs;
1452 return fcLens[best1];
1453 }
1454
1455 //by marshmellow - demodulate PSK1 wave
1456 //uses wave lengths (# Samples)
1457 int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
1458 {
1459 if (size == 0) return -1;
1460 uint16_t loopCnt = 4096; //don't need to loop through entire array...
1461 if (*size<loopCnt) loopCnt = *size;
1462
1463 size_t numBits=0;
1464 uint8_t curPhase = *invert;
1465 size_t i, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0;
1466 uint8_t fc=0, fullWaveLen=0, tol=1;
1467 uint16_t errCnt=0, waveLenCnt=0;
1468 fc = countFC(dest, *size, 0);
1469 if (fc!=2 && fc!=4 && fc!=8) return -1;
1470 //PrintAndLog("DEBUG: FC: %d",fc);
1471 *clock = DetectPSKClock(dest, *size, *clock);
1472 if (*clock == 0) return -1;
1473 int avgWaveVal=0, lastAvgWaveVal=0;
1474 //find first phase shift
1475 for (i=0; i<loopCnt; i++){
1476 if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
1477 waveEnd = i+1;
1478 //PrintAndLog("DEBUG: waveEnd: %d",waveEnd);
1479 waveLenCnt = waveEnd-waveStart;
1480 if (waveLenCnt > fc && waveStart > fc && !(waveLenCnt > fc+2)){ //not first peak and is a large wave but not out of whack
1481 lastAvgWaveVal = avgWaveVal/(waveLenCnt);
1482 firstFullWave = waveStart;
1483 fullWaveLen=waveLenCnt;
1484 //if average wave value is > graph 0 then it is an up wave or a 1
1485 if (lastAvgWaveVal > 123) curPhase ^= 1; //fudge graph 0 a little 123 vs 128
1486 break;
1487 }
1488 waveStart = i+1;
1489 avgWaveVal = 0;
1490 }
1491 avgWaveVal += dest[i+2];
1492 }
1493 if (firstFullWave == 0) {
1494 // no phase shift detected - could be all 1's or 0's - doesn't matter where we start
1495 // so skip a little to ensure we are past any Start Signal
1496 firstFullWave = 160;
1497 memset(dest, curPhase, firstFullWave / *clock);
1498 } else {
1499 memset(dest, curPhase^1, firstFullWave / *clock);
1500 }
1501 //advance bits
1502 numBits += (firstFullWave / *clock);
1503 //set start of wave as clock align
1504 lastClkBit = firstFullWave;
1505 if (g_debugMode==2) prnt("DEBUG PSK: firstFullWave: %u, waveLen: %u",firstFullWave,fullWaveLen);
1506 if (g_debugMode==2) prnt("DEBUG: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit,(unsigned int) fc);
1507 waveStart = 0;
1508 dest[numBits++] = curPhase; //set first read bit
1509 for (i = firstFullWave + fullWaveLen - 1; i < *size-3; i++){
1510 //top edge of wave = start of new wave
1511 if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
1512 if (waveStart == 0) {
1513 waveStart = i+1;
1514 waveLenCnt = 0;
1515 avgWaveVal = dest[i+1];
1516 } else { //waveEnd
1517 waveEnd = i+1;
1518 waveLenCnt = waveEnd-waveStart;
1519 lastAvgWaveVal = avgWaveVal/waveLenCnt;
1520 if (waveLenCnt > fc){
1521 //PrintAndLog("DEBUG: avgWaveVal: %d, waveSum: %d",lastAvgWaveVal,avgWaveVal);
1522 //this wave is a phase shift
1523 //PrintAndLog("DEBUG: phase shift at: %d, len: %d, nextClk: %d, i: %d, fc: %d",waveStart,waveLenCnt,lastClkBit+*clock-tol,i+1,fc);
1524 if (i+1 >= lastClkBit + *clock - tol){ //should be a clock bit
1525 curPhase ^= 1;
1526 dest[numBits++] = curPhase;
1527 lastClkBit += *clock;
1528 } else if (i < lastClkBit+10+fc){
1529 //noise after a phase shift - ignore
1530 } else { //phase shift before supposed to based on clock
1531 errCnt++;
1532 dest[numBits++] = 7;
1533 }
1534 } else if (i+1 > lastClkBit + *clock + tol + fc){
1535 lastClkBit += *clock; //no phase shift but clock bit
1536 dest[numBits++] = curPhase;
1537 }
1538 avgWaveVal = 0;
1539 waveStart = i+1;
1540 }
1541 }
1542 avgWaveVal += dest[i+1];
1543 }
1544 *size = numBits;
1545 return errCnt;
1546 }
1547
1548 //by marshmellow
1549 //attempt to identify a Sequence Terminator in ASK modulated raw wave
1550 bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
1551 size_t bufsize = *size;
1552 //need to loop through all samples and identify our clock, look for the ST pattern
1553 uint8_t fndClk[] = {8,16,32,40,50,64,128};
1554 int clk = 0;
1555 int tol = 0;
1556 int i, j, skip, start, end, low, high, minClk, waveStart;
1557 bool complete = false;
1558 int tmpbuff[bufsize / 32]; //guess rf/32 clock, if click is smaller we will only have room for a fraction of the samples captured
1559 int waveLen[bufsize / 32]; // if clock is larger then we waste memory in array size that is not needed...
1560 size_t testsize = (bufsize < 512) ? bufsize : 512;
1561 int phaseoff = 0;
1562 high = low = 128;
1563 memset(tmpbuff, 0, sizeof(tmpbuff));
1564
1565 if ( getHiLo(buffer, testsize, &high, &low, 80, 80) == -1 ) {
1566 if (g_debugMode==2) prnt("DEBUG STT: just noise detected - quitting");
1567 return false; //just noise
1568 }
1569 i = 0;
1570 j = 0;
1571 minClk = 255;
1572 // get to first full low to prime loop and skip incomplete first pulse
1573 while ((buffer[i] < high) && (i < bufsize))
1574 ++i;
1575 while ((buffer[i] > low) && (i < bufsize))
1576 ++i;
1577 skip = i;
1578
1579 // populate tmpbuff buffer with pulse lengths
1580 while (i < bufsize) {
1581 // measure from low to low
1582 while ((buffer[i] > low) && (i < bufsize))
1583 ++i;
1584 start= i;
1585 while ((buffer[i] < high) && (i < bufsize))
1586 ++i;
1587 //first high point for this wave
1588 waveStart = i;
1589 while ((buffer[i] > low) && (i < bufsize))
1590 ++i;
1591 if (j >= (bufsize/32)) {
1592 break;
1593 }
1594 waveLen[j] = i - waveStart; //first high to first low
1595 tmpbuff[j++] = i - start;
1596 if (i-start < minClk && i < bufsize) {
1597 minClk = i - start;
1598 }
1599 }
1600 // set clock - might be able to get this externally and remove this work...
1601 if (!clk) {
1602 for (uint8_t clkCnt = 0; clkCnt<7; clkCnt++) {
1603 tol = fndClk[clkCnt]/8;
1604 if (minClk >= fndClk[clkCnt]-tol && minClk <= fndClk[clkCnt]+1) {
1605 clk=fndClk[clkCnt];
1606 break;
1607 }
1608 }
1609 // clock not found - ERROR
1610 if (!clk) {
1611 if (g_debugMode==2) prnt("DEBUG STT: clock not found - quitting");
1612 return false;
1613 }
1614 } else tol = clk/8;
1615
1616 *foundclock = clk;
1617
1618 // look for Sequence Terminator - should be pulses of clk*(1 or 1.5), clk*2, clk*(1.5 or 2)
1619 start = -1;
1620 for (i = 0; i < j - 4; ++i) {
1621 skip += tmpbuff[i];
1622 if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior
1623 if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol && waveLen[i+1] > clk*3/2-tol) { //2 clocks and wave size is 1 1/2
1624 if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol && waveLen[i+2] > clk-tol) { //1 1/2 to 2 clocks and at least one full clock wave
1625 if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
1626 start = i + 3;
1627 break;
1628 }
1629 }
1630 }
1631 }
1632 }
1633 // first ST not found - ERROR
1634 if (start < 0) {
1635 if (g_debugMode==2) prnt("DEBUG STT: first STT not found - quitting");
1636 return false;
1637 } else {
1638 if (g_debugMode==2) prnt("DEBUG STT: first STT found at: %d, j=%d",start, j);
1639 }
1640 if (waveLen[i+2] > clk*1+tol)
1641 phaseoff = 0;
1642 else
1643 phaseoff = clk/2;
1644
1645 // skip over the remainder of ST
1646 skip += clk*7/2; //3.5 clocks from tmpbuff[i] = end of st - also aligns for ending point
1647
1648 // now do it again to find the end
1649 end = skip;
1650 for (i += 3; i < j - 4; ++i) {
1651 end += tmpbuff[i];
1652 if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior
1653 if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol && waveLen[i+1] > clk*3/2-tol) { //2 clocks and wave size is 1 1/2
1654 if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol && waveLen[i+2] > clk-tol) { //1 1/2 to 2 clocks and at least one full clock wave
1655 if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
1656 complete = true;
1657 break;
1658 }
1659 }
1660 }
1661 }
1662 }
1663 end -= phaseoff;
1664 //didn't find second ST - ERROR
1665 if (!complete) {
1666 if (g_debugMode==2) prnt("DEBUG STT: second STT not found - quitting");
1667 return false;
1668 }
1669 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);
1670 //now begin to trim out ST so we can use normal demod cmds
1671 start = skip;
1672 size_t datalen = end - start;
1673 // check validity of datalen (should be even clock increments) - use a tolerance of up to 1/8th a clock
1674 if ( clk - (datalen % clk) <= clk/8) {
1675 // padd the amount off - could be problematic... but shouldn't happen often
1676 datalen += clk - (datalen % clk);
1677 } else if ( (datalen % clk) <= clk/8 ) {
1678 // padd the amount off - could be problematic... but shouldn't happen often
1679 datalen -= datalen % clk;
1680 } else {
1681 if (g_debugMode==2) prnt("DEBUG STT: datalen not divisible by clk: %u %% %d = %d - quitting", datalen, clk, datalen % clk);
1682 return false;
1683 }
1684 // if datalen is less than one t55xx block - ERROR
1685 if (datalen/clk < 8*4) {
1686 if (g_debugMode==2) prnt("DEBUG STT: datalen is less than 1 full t55xx block - quitting");
1687 return false;
1688 }
1689 size_t dataloc = start;
1690 if (buffer[dataloc-(clk*4)-(clk/8)] <= low && buffer[dataloc] <= low && buffer[dataloc-(clk*4)] >= high) {
1691 //we have low drift (and a low just before the ST and a low just after the ST) - compensate by backing up the start
1692 for ( i=0; i <= (clk/8); ++i ) {
1693 if ( buffer[dataloc - (clk*4) - i] <= low ) {
1694 dataloc -= i;
1695 break;
1696 }
1697 }
1698 }
1699
1700 size_t newloc = 0;
1701 i=0;
1702 if (g_debugMode==2) prnt("DEBUG STT: Starting STT trim - start: %d, datalen: %d ",dataloc, datalen);
1703
1704 // warning - overwriting buffer given with raw wave data with ST removed...
1705 while ( dataloc < bufsize-(clk/2) ) {
1706 //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)
1707 if (buffer[dataloc]<high && buffer[dataloc]>low && buffer[dataloc+3]<high && buffer[dataloc+3]>low) {
1708 for(i=0; i < clk/2-tol; ++i) {
1709 buffer[dataloc+i] = high+5;
1710 }
1711 }
1712 for (i=0; i<datalen; ++i) {
1713 if (i+newloc < bufsize) {
1714 if (i+newloc < dataloc)
1715 buffer[i+newloc] = buffer[dataloc];
1716
1717 dataloc++;
1718 }
1719 }
1720 newloc += i;
1721 //skip next ST - we just assume it will be there from now on...
1722 if (g_debugMode==2) prnt("DEBUG STT: skipping STT at %d to %d", dataloc, dataloc+(clk*4));
1723 dataloc += clk*4;
1724 }
1725 *size = newloc;
1726 return true;
1727 }
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