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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 // Sanity check. If preamble length is bigger than bitstream length.
152 if ( *size <= pLen ) return 0;
153
154 uint8_t foundCnt=0;
155 for (int idx=0; idx < *size - pLen; idx++){
156 if (memcmp(BitStream+idx, preamble, pLen) == 0){
157 //first index found
158 foundCnt++;
159 if (foundCnt == 1){
160 *startIdx = idx;
161 }
162 if (foundCnt == 2){
163 *size = idx - *startIdx;
164 return 1;
165 }
166 }
167 }
168 return 0;
169 }
170
171 //by marshmellow
172 //takes 1s and 0s and searches for EM410x format - output EM ID
173 uint8_t Em410xDecode(uint8_t *BitStream, size_t *size, size_t *startIdx, uint32_t *hi, uint64_t *lo)
174 {
175 //no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
176 // otherwise could be a void with no arguments
177 //set defaults
178 uint32_t i = 0;
179 if (BitStream[1]>1) return 0; //allow only 1s and 0s
180
181 // 111111111 bit pattern represent start of frame
182 // include 0 in front to help get start pos
183 uint8_t preamble[] = {0,1,1,1,1,1,1,1,1,1};
184 uint32_t idx = 0;
185 uint32_t parityBits = 0;
186 uint8_t errChk = 0;
187 uint8_t FmtLen = 10;
188 *startIdx = 0;
189 errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, startIdx);
190 if (errChk == 0 || *size < 64) return 0;
191 if (*size > 64) FmtLen = 22;
192 *startIdx += 1; //get rid of 0 from preamble
193 idx = *startIdx + 9;
194 for (i=0; i<FmtLen; i++){ //loop through 10 or 22 sets of 5 bits (50-10p = 40 bits or 88 bits)
195 parityBits = bytebits_to_byte(BitStream+(i*5)+idx,5);
196 //check even parity - quit if failed
197 if (parityTest(parityBits, 5, 0) == 0) return 0;
198 //set uint64 with ID from BitStream
199 for (uint8_t ii=0; ii<4; ii++){
200 *hi = (*hi << 1) | (*lo >> 63);
201 *lo = (*lo << 1) | (BitStream[(i*5)+ii+idx]);
202 }
203 }
204 if (errChk != 0) return 1;
205 //skip last 5 bit parity test for simplicity.
206 // *size = 64 | 128;
207 return 0;
208 }
209
210 //by marshmellow
211 //demodulates strong heavily clipped samples
212 int cleanAskRawDemod(uint8_t *BinStream, size_t *size, int clk, int invert, int high, int low)
213 {
214 size_t bitCnt=0, smplCnt=0, errCnt=0;
215 uint8_t waveHigh = 0;
216 for (size_t i=0; i < *size; i++){
217 if (BinStream[i] >= high && waveHigh){
218 smplCnt++;
219 } else if (BinStream[i] <= low && !waveHigh){
220 smplCnt++;
221 } else { //transition
222 if ((BinStream[i] >= high && !waveHigh) || (BinStream[i] <= low && waveHigh)){
223 if (smplCnt > clk-(clk/4)-1) { //full clock
224 if (smplCnt > clk + (clk/4)+1) { //too many samples
225 errCnt++;
226 if (g_debugMode==2) prnt("DEBUG ASK: Modulation Error at: %u", i);
227 BinStream[bitCnt++]=7;
228 } else if (waveHigh) {
229 BinStream[bitCnt++] = invert;
230 BinStream[bitCnt++] = invert;
231 } else if (!waveHigh) {
232 BinStream[bitCnt++] = invert ^ 1;
233 BinStream[bitCnt++] = invert ^ 1;
234 }
235 waveHigh ^= 1;
236 smplCnt = 0;
237 } else if (smplCnt > (clk/2) - (clk/4)-1) {
238 if (waveHigh) {
239 BinStream[bitCnt++] = invert;
240 } else if (!waveHigh) {
241 BinStream[bitCnt++] = invert ^ 1;
242 }
243 waveHigh ^= 1;
244 smplCnt = 0;
245 } else if (!bitCnt) {
246 //first bit
247 waveHigh = (BinStream[i] >= high);
248 smplCnt = 1;
249 } else {
250 smplCnt++;
251 //transition bit oops
252 }
253 } else { //haven't hit new high or new low yet
254 smplCnt++;
255 }
256 }
257 }
258 *size = bitCnt;
259 return errCnt;
260 }
261
262 //by marshmellow
263 void askAmp(uint8_t *BitStream, size_t size)
264 {
265 uint8_t Last = 128;
266 for(size_t i = 1; i<size; i++){
267 if (BitStream[i]-BitStream[i-1]>=30) //large jump up
268 Last = 255;
269 else if(BitStream[i-1]-BitStream[i]>=20) //large jump down
270 Last = 0;
271
272 BitStream[i-1] = Last;
273 }
274 return;
275 }
276
277 //by marshmellow
278 //attempts to demodulate ask modulations, askType == 0 for ask/raw, askType==1 for ask/manchester
279 int askdemod(uint8_t *BinStream, size_t *size, int *clk, int *invert, int maxErr, uint8_t amp, uint8_t askType)
280 {
281 if (*size==0) return -1;
282 int start = DetectASKClock(BinStream, *size, clk, maxErr); //clock default
283 if (*clk==0 || start < 0) return -3;
284 if (*invert != 1) *invert = 0;
285 if (amp==1) askAmp(BinStream, *size);
286 if (g_debugMode==2) prnt("DEBUG ASK: clk %d, beststart %d, amp %d", *clk, start, amp);
287
288 uint8_t initLoopMax = 255;
289 if (initLoopMax > *size) initLoopMax = *size;
290 // Detect high and lows
291 //25% clip in case highs and lows aren't clipped [marshmellow]
292 int high, low;
293 if (getHiLo(BinStream, initLoopMax, &high, &low, 75, 75) < 1)
294 return -2; //just noise
295
296 size_t errCnt = 0;
297 // if clean clipped waves detected run alternate demod
298 if (DetectCleanAskWave(BinStream, *size, high, low)) {
299 if (g_debugMode==2) prnt("DEBUG ASK: Clean Wave Detected - using clean wave demod");
300 errCnt = cleanAskRawDemod(BinStream, size, *clk, *invert, high, low);
301 if (askType) //askman
302 return manrawdecode(BinStream, size, 0);
303 else //askraw
304 return errCnt;
305 }
306 if (g_debugMode==2) prnt("DEBUG ASK: Weak Wave Detected - using weak wave demod");
307
308 int lastBit; //set first clock check - can go negative
309 size_t i, bitnum = 0; //output counter
310 uint8_t midBit = 0;
311 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
312 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
313 size_t MaxBits = 3072; //max bits to collect
314 lastBit = start - *clk;
315
316 for (i = start; i < *size; ++i) {
317 if (i-lastBit >= *clk-tol){
318 if (BinStream[i] >= high) {
319 BinStream[bitnum++] = *invert;
320 } else if (BinStream[i] <= low) {
321 BinStream[bitnum++] = *invert ^ 1;
322 } else if (i-lastBit >= *clk+tol) {
323 if (bitnum > 0) {
324 if (g_debugMode==2) prnt("DEBUG ASK: Modulation Error at: %u", i);
325 BinStream[bitnum++]=7;
326 errCnt++;
327 }
328 } else { //in tolerance - looking for peak
329 continue;
330 }
331 midBit = 0;
332 lastBit += *clk;
333 } else if (i-lastBit >= (*clk/2-tol) && !midBit && !askType){
334 if (BinStream[i] >= high) {
335 BinStream[bitnum++] = *invert;
336 } else if (BinStream[i] <= low) {
337 BinStream[bitnum++] = *invert ^ 1;
338 } else if (i-lastBit >= *clk/2+tol) {
339 BinStream[bitnum] = BinStream[bitnum-1];
340 bitnum++;
341 } else { //in tolerance - looking for peak
342 continue;
343 }
344 midBit = 1;
345 }
346 if (bitnum >= MaxBits) break;
347 }
348 *size = bitnum;
349 return errCnt;
350 }
351
352 //by marshmellow
353 //take 10 and 01 and manchester decode
354 //run through 2 times and take least errCnt
355 int manrawdecode(uint8_t * BitStream, size_t *size, uint8_t invert)
356 {
357 uint16_t bitnum=0, MaxBits = 512, errCnt = 0;
358 size_t i, ii;
359 uint16_t bestErr = 1000, bestRun = 0;
360 if (*size < 16) return -1;
361 //find correct start position [alignment]
362 for (ii=0;ii<2;++ii){
363 for (i=ii; i<*size-3; i+=2)
364 if (BitStream[i]==BitStream[i+1])
365 errCnt++;
366
367 if (bestErr>errCnt){
368 bestErr=errCnt;
369 bestRun=ii;
370 }
371 errCnt=0;
372 }
373 //decode
374 for (i=bestRun; i < *size-3; i+=2){
375 if(BitStream[i] == 1 && (BitStream[i+1] == 0)){
376 BitStream[bitnum++]=invert;
377 } else if((BitStream[i] == 0) && BitStream[i+1] == 1){
378 BitStream[bitnum++]=invert^1;
379 } else {
380 BitStream[bitnum++]=7;
381 }
382 if(bitnum>MaxBits) break;
383 }
384 *size=bitnum;
385 return bestErr;
386 }
387
388 uint32_t manchesterEncode2Bytes(uint16_t datain) {
389 uint32_t output = 0;
390 uint8_t curBit = 0;
391 for (uint8_t i=0; i<16; i++) {
392 curBit = (datain >> (15-i) & 1);
393 output |= (1<<(((15-i)*2)+curBit));
394 }
395 return output;
396 }
397
398 //by marshmellow
399 //encode binary data into binary manchester
400 int ManchesterEncode(uint8_t *BitStream, size_t size)
401 {
402 size_t modIdx=20000, i=0;
403 if (size>modIdx) return -1;
404 for (size_t idx=0; idx < size; idx++){
405 BitStream[idx+modIdx++] = BitStream[idx];
406 BitStream[idx+modIdx++] = BitStream[idx]^1;
407 }
408 for (; i<(size*2); i++){
409 BitStream[i] = BitStream[i+20000];
410 }
411 return i;
412 }
413
414 //by marshmellow
415 //take 01 or 10 = 1 and 11 or 00 = 0
416 //check for phase errors - should never have 111 or 000 should be 01001011 or 10110100 for 1010
417 //decodes biphase or if inverted it is AKA conditional dephase encoding AKA differential manchester encoding
418 int BiphaseRawDecode(uint8_t *BitStream, size_t *size, int offset, int invert)
419 {
420 uint16_t bitnum = 0;
421 uint16_t errCnt = 0;
422 size_t i = offset;
423 uint16_t MaxBits=512;
424 //if not enough samples - error
425 if (*size < 51) return -1;
426 //check for phase change faults - skip one sample if faulty
427 uint8_t offsetA = 1, offsetB = 1;
428 for (; i<48; i+=2){
429 if (BitStream[i+1]==BitStream[i+2]) offsetA=0;
430 if (BitStream[i+2]==BitStream[i+3]) offsetB=0;
431 }
432 if (!offsetA && offsetB) offset++;
433 for (i=offset; i<*size-3; i+=2){
434 //check for phase error
435 if (BitStream[i+1]==BitStream[i+2]) {
436 BitStream[bitnum++]=7;
437 errCnt++;
438 }
439 if((BitStream[i]==1 && BitStream[i+1]==0) || (BitStream[i]==0 && BitStream[i+1]==1)){
440 BitStream[bitnum++]=1^invert;
441 } else if((BitStream[i]==0 && BitStream[i+1]==0) || (BitStream[i]==1 && BitStream[i+1]==1)){
442 BitStream[bitnum++]=invert;
443 } else {
444 BitStream[bitnum++]=7;
445 errCnt++;
446 }
447 if(bitnum>MaxBits) break;
448 }
449 *size=bitnum;
450 return errCnt;
451 }
452
453 // by marshmellow
454 // demod gProxIIDemod
455 // error returns as -x
456 // success returns start position in BitStream
457 // BitStream must contain previously askrawdemod and biphasedemoded data
458 int gProxII_Demod(uint8_t BitStream[], size_t *size)
459 {
460 size_t startIdx=0;
461 uint8_t preamble[] = {1,1,1,1,1,0};
462
463 uint8_t errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, &startIdx);
464 if (errChk == 0) return -3; //preamble not found
465 if (*size != 96) return -2; //should have found 96 bits
466 //check first 6 spacer bits to verify format
467 if (!BitStream[startIdx+5] && !BitStream[startIdx+10] && !BitStream[startIdx+15] && !BitStream[startIdx+20] && !BitStream[startIdx+25] && !BitStream[startIdx+30]){
468 //confirmed proper separator bits found
469 //return start position
470 return (int) startIdx;
471 }
472 return -5; //spacer bits not found - not a valid gproxII
473 }
474
475 //translate wave to 11111100000 (1 for each short wave [higher freq] 0 for each long wave [lower freq])
476 size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow)
477 {
478 size_t last_transition = 0;
479 size_t idx = 1;
480 //uint32_t maxVal=0;
481 if (fchigh==0) fchigh=10;
482 if (fclow==0) fclow=8;
483 //set the threshold close to 0 (graph) or 128 std to avoid static
484 uint8_t threshold_value = 123;
485 size_t preLastSample = 0;
486 size_t LastSample = 0;
487 size_t currSample = 0;
488 // sync to first lo-hi transition, and threshold
489
490 // Need to threshold first sample
491 // skip 160 samples to allow antenna/samples to settle
492 if(dest[160] < threshold_value) dest[0] = 0;
493 else dest[0] = 1;
494
495 size_t numBits = 0;
496 // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
497 // or 10 (fc/10) cycles but in practice due to noise etc we may end up with anywhere
498 // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
499 // (could also be fc/5 && fc/7 for fsk1 = 4-9)
500 for(idx = 161; idx < size-20; idx++) {
501 // threshold current value
502
503 if (dest[idx] < threshold_value) dest[idx] = 0;
504 else dest[idx] = 1;
505
506 // Check for 0->1 transition
507 if (dest[idx-1] < dest[idx]) {
508 preLastSample = LastSample;
509 LastSample = currSample;
510 currSample = idx-last_transition;
511 if (currSample < (fclow-2)) { //0-5 = garbage noise (or 0-3)
512 //do nothing with extra garbage
513 } else if (currSample < (fchigh-1)) { //6-8 = 8 sample waves (or 3-6 = 5)
514 //correct previous 9 wave surrounded by 8 waves (or 6 surrounded by 5)
515 if (LastSample > (fchigh-2) && (preLastSample < (fchigh-1) || preLastSample == 0 )){
516 dest[numBits-1]=1;
517 }
518 dest[numBits++]=1;
519
520 } else if (currSample > (fchigh) && !numBits) { //12 + and first bit = unusable garbage
521 //do nothing with beginning garbage
522 } 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)
523 dest[numBits++]=1;
524 } else { //9+ = 10 sample waves (or 6+ = 7)
525 dest[numBits++]=0;
526 }
527 last_transition = idx;
528 }
529 }
530 return numBits; //Actually, it returns the number of bytes, but each byte represents a bit: 1 or 0
531 }
532
533 //translate 11111100000 to 10
534 //rfLen = clock, fchigh = larger field clock, fclow = smaller field clock
535 size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen,
536 uint8_t invert, uint8_t fchigh, uint8_t fclow)
537 {
538 uint8_t lastval=dest[0];
539 size_t idx=0;
540 size_t numBits=0;
541 uint32_t n=1;
542 for( idx=1; idx < size; idx++) {
543 n++;
544 if (dest[idx]==lastval) continue; //skip until we hit a transition
545
546 //find out how many bits (n) we collected
547 //if lastval was 1, we have a 1->0 crossing
548 if (dest[idx-1]==1) {
549 n = (n * fclow + rfLen/2) / rfLen;
550 } else {// 0->1 crossing
551 n = (n * fchigh + rfLen/2) / rfLen;
552 }
553 if (n == 0) n = 1;
554
555 //add to our destination the bits we collected
556 memset(dest+numBits, dest[idx-1]^invert , n);
557 numBits += n;
558 n=0;
559 lastval=dest[idx];
560 }//end for
561 // if valid extra bits at the end were all the same frequency - add them in
562 if (n > rfLen/fchigh) {
563 if (dest[idx-2]==1) {
564 n = (n * fclow + rfLen/2) / rfLen;
565 } else {
566 n = (n * fchigh + rfLen/2) / rfLen;
567 }
568 memset(dest+numBits, dest[idx-1]^invert , n);
569 numBits += n;
570 }
571 return numBits;
572 }
573
574 //by marshmellow (from holiman's base)
575 // full fsk demod from GraphBuffer wave to decoded 1s and 0s (no mandemod)
576 int fskdemod(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow)
577 {
578 // FSK demodulator
579 size = fsk_wave_demod(dest, size, fchigh, fclow);
580 size = aggregate_bits(dest, size, rfLen, invert, fchigh, fclow);
581 return size;
582 }
583
584 // loop to get raw HID waveform then FSK demodulate the TAG ID from it
585 int HIDdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
586 {
587 if (justNoise(dest, *size)) return -1;
588
589 size_t numStart=0, size2=*size, startIdx=0;
590 // FSK demodulator
591 *size = fskdemod(dest, size2,50,1,10,8); //fsk2a
592 if (*size < 96*2) return -2;
593 // 00011101 bit pattern represent start of frame, 01 pattern represents a 0 and 10 represents a 1
594 uint8_t preamble[] = {0,0,0,1,1,1,0,1};
595 // find bitstring in array
596 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
597 if (errChk == 0) return -3; //preamble not found
598
599 numStart = startIdx + sizeof(preamble);
600 // final loop, go over previously decoded FSK data and manchester decode into usable tag ID
601 for (size_t idx = numStart; (idx-numStart) < *size - sizeof(preamble); idx+=2){
602 if (dest[idx] == dest[idx+1]){
603 return -4; //not manchester data
604 }
605 *hi2 = (*hi2<<1)|(*hi>>31);
606 *hi = (*hi<<1)|(*lo>>31);
607 //Then, shift in a 0 or one into low
608 if (dest[idx] && !dest[idx+1]) // 1 0
609 *lo=(*lo<<1)|1;
610 else // 0 1
611 *lo=(*lo<<1)|0;
612 }
613 return (int)startIdx;
614 }
615
616 // loop to get raw paradox waveform then FSK demodulate the TAG ID from it
617 int ParadoxdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
618 {
619 if (justNoise(dest, *size)) return -1;
620
621 size_t numStart=0, size2=*size, startIdx=0;
622 // FSK demodulator
623 *size = fskdemod(dest, size2,50,1,10,8); //fsk2a
624 if (*size < 96) return -2;
625
626 // 00001111 bit pattern represent start of frame, 01 pattern represents a 0 and 10 represents a 1
627 uint8_t preamble[] = {0,0,0,0,1,1,1,1};
628
629 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
630 if (errChk == 0) return -3; //preamble not found
631
632 numStart = startIdx + sizeof(preamble);
633 // final loop, go over previously decoded FSK data and manchester decode into usable tag ID
634 for (size_t idx = numStart; (idx-numStart) < *size - sizeof(preamble); idx+=2){
635 if (dest[idx] == dest[idx+1])
636 return -4; //not manchester data
637 *hi2 = (*hi2<<1)|(*hi>>31);
638 *hi = (*hi<<1)|(*lo>>31);
639 //Then, shift in a 0 or one into low
640 if (dest[idx] && !dest[idx+1]) // 1 0
641 *lo=(*lo<<1)|1;
642 else // 0 1
643 *lo=(*lo<<1)|0;
644 }
645 return (int)startIdx;
646 }
647
648 int IOdemodFSK(uint8_t *dest, size_t size)
649 {
650 if (justNoise(dest, size)) return -1;
651 //make sure buffer has data
652 if (size < 66*64) return -2;
653 // FSK demodulator
654 size = fskdemod(dest, size, 64, 1, 10, 8); // FSK2a RF/64
655 if (size < 65) return -3; //did we get a good demod?
656 //Index map
657 //0 10 20 30 40 50 60
658 //| | | | | | |
659 //01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
660 //-----------------------------------------------------------------------------
661 //00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
662 //
663 //XSF(version)facility:codeone+codetwo
664 //Handle the data
665 size_t startIdx = 0;
666 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,1};
667 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), &size, &startIdx);
668 if (errChk == 0) return -4; //preamble not found
669
670 if (!dest[startIdx+8] && dest[startIdx+17]==1 && dest[startIdx+26]==1 && dest[startIdx+35]==1 && dest[startIdx+44]==1 && dest[startIdx+53]==1){
671 //confirmed proper separator bits found
672 //return start position
673 return (int) startIdx;
674 }
675 return -5;
676 }
677
678 // by marshmellow
679 // find viking preamble 0xF200 in already demoded data
680 int VikingDemod_AM(uint8_t *dest, size_t *size) {
681 //make sure buffer has data
682 if (*size < 64*2) return -2;
683
684 size_t startIdx = 0;
685 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};
686 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
687 if (errChk == 0) return -4; //preamble not found
688 uint32_t checkCalc = bytebits_to_byte(dest+startIdx,8) ^ bytebits_to_byte(dest+startIdx+8,8) ^ bytebits_to_byte(dest+startIdx+16,8)
689 ^ bytebits_to_byte(dest+startIdx+24,8) ^ bytebits_to_byte(dest+startIdx+32,8) ^ bytebits_to_byte(dest+startIdx+40,8)
690 ^ bytebits_to_byte(dest+startIdx+48,8) ^ bytebits_to_byte(dest+startIdx+56,8);
691 if ( checkCalc != 0xA8 ) return -5;
692 if (*size != 64) return -6;
693 //return start position
694 return (int) startIdx;
695 }
696
697 // find presco preamble 0x10D in already demoded data
698 int PrescoDemod(uint8_t *dest, size_t *size) {
699 //make sure buffer has data
700 if (*size < 64*2) return -2;
701
702 size_t startIdx = 0;
703 uint8_t preamble[] = {1,0,0,0,0,1,1,0,1,0,0,0,0,0,0,0,0,0,0,0};
704 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
705 if (errChk == 0) return -4; //preamble not found
706 //return start position
707 return (int) startIdx;
708 }
709
710 // Ask/Biphase Demod then try to locate an ISO 11784/85 ID
711 // BitStream must contain previously askrawdemod and biphasedemoded data
712 int FDXBdemodBI(uint8_t *dest, size_t *size)
713 {
714 //make sure buffer has enough data
715 if (*size < 128) return -1;
716
717 size_t startIdx = 0;
718 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,1};
719
720 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
721 if (errChk == 0) return -2; //preamble not found
722 return (int)startIdx;
723 }
724
725 // by marshmellow
726 // FSK Demod then try to locate an AWID ID
727 int AWIDdemodFSK(uint8_t *dest, size_t *size)
728 {
729 //make sure buffer has enough data
730 if (*size < 96*50) return -1;
731
732 if (justNoise(dest, *size)) return -2;
733
734 // FSK demodulator
735 *size = fskdemod(dest, *size, 50, 1, 10, 8); // fsk2a RF/50
736 if (*size < 96) return -3; //did we get a good demod?
737
738 uint8_t preamble[] = {0,0,0,0,0,0,0,1};
739 size_t startIdx = 0;
740 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
741 if (errChk == 0) return -4; //preamble not found
742 if (*size != 96) return -5;
743 return (int)startIdx;
744 }
745
746 // by marshmellow
747 // FSK Demod then try to locate a Farpointe Data (pyramid) ID
748 int PyramiddemodFSK(uint8_t *dest, size_t *size)
749 {
750 //make sure buffer has data
751 if (*size < 128*50) return -5;
752
753 //test samples are not just noise
754 if (justNoise(dest, *size)) return -1;
755
756 // FSK demodulator
757 *size = fskdemod(dest, *size, 50, 1, 10, 8); // fsk2a RF/50
758 if (*size < 128) return -2; //did we get a good demod?
759
760 uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
761 size_t startIdx = 0;
762 uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
763 if (errChk == 0) return -4; //preamble not found
764 if (*size != 128) return -3;
765 return (int)startIdx;
766 }
767
768 // by marshmellow
769 // to detect a wave that has heavily clipped (clean) samples
770 uint8_t DetectCleanAskWave(uint8_t dest[], size_t size, uint8_t high, uint8_t low)
771 {
772 bool allArePeaks = true;
773 uint16_t cntPeaks=0;
774 size_t loopEnd = 512+160;
775 if (loopEnd > size) loopEnd = size;
776 for (size_t i=160; i<loopEnd; i++){
777 if (dest[i]>low && dest[i]<high)
778 allArePeaks = false;
779 else
780 cntPeaks++;
781 }
782 if (!allArePeaks){
783 if (cntPeaks > 300) return true;
784 }
785 return allArePeaks;
786 }
787 // by marshmellow
788 // to help detect clocks on heavily clipped samples
789 // based on count of low to low
790 int DetectStrongAskClock(uint8_t dest[], size_t size, uint8_t high, uint8_t low)
791 {
792 uint8_t fndClk[] = {8,16,32,40,50,64,128};
793 size_t startwave;
794 size_t i = 100;
795 size_t minClk = 255;
796 // get to first full low to prime loop and skip incomplete first pulse
797 while ((dest[i] < high) && (i < size))
798 ++i;
799 while ((dest[i] > low) && (i < size))
800 ++i;
801
802 // loop through all samples
803 while (i < size) {
804 // measure from low to low
805 while ((dest[i] > low) && (i < size))
806 ++i;
807 startwave= i;
808 while ((dest[i] < high) && (i < size))
809 ++i;
810 while ((dest[i] > low) && (i < size))
811 ++i;
812 //get minimum measured distance
813 if (i-startwave < minClk && i < size)
814 minClk = i - startwave;
815 }
816 // set clock
817 if (g_debugMode==2) prnt("DEBUG ASK: detectstrongASKclk smallest wave: %d",minClk);
818 for (uint8_t clkCnt = 0; clkCnt<7; clkCnt++) {
819 if (minClk >= fndClk[clkCnt]-(fndClk[clkCnt]/8) && minClk <= fndClk[clkCnt]+1)
820 return fndClk[clkCnt];
821 }
822 return 0;
823 }
824
825 // by marshmellow
826 // not perfect especially with lower clocks or VERY good antennas (heavy wave clipping)
827 // maybe somehow adjust peak trimming value based on samples to fix?
828 // return start index of best starting position for that clock and return clock (by reference)
829 int DetectASKClock(uint8_t dest[], size_t size, int *clock, int maxErr)
830 {
831 size_t i=1;
832 uint8_t clk[] = {255,8,16,32,40,50,64,100,128,255};
833 uint8_t clkEnd = 9;
834 uint8_t loopCnt = 255; //don't need to loop through entire array...
835 if (size <= loopCnt+60) return -1; //not enough samples
836 size -= 60; //sometimes there is a strange end wave - filter out this....
837 //if we already have a valid clock
838 uint8_t clockFnd=0;
839 for (;i<clkEnd;++i)
840 if (clk[i] == *clock) clockFnd = i;
841 //clock found but continue to find best startpos
842
843 //get high and low peak
844 int peak, low;
845 if (getHiLo(dest, loopCnt, &peak, &low, 75, 75) < 1) return -1;
846
847 //test for large clean peaks
848 if (!clockFnd){
849 if (DetectCleanAskWave(dest, size, peak, low)==1){
850 int ans = DetectStrongAskClock(dest, size, peak, low);
851 if (g_debugMode==2) prnt("DEBUG ASK: detectaskclk Clean Ask Wave Detected: clk %d",ans);
852 for (i=clkEnd-1; i>0; i--){
853 if (clk[i] == ans) {
854 *clock = ans;
855 //clockFnd = i;
856 return 0; // for strong waves i don't use the 'best start position' yet...
857 //break; //clock found but continue to find best startpos [not yet]
858 }
859 }
860 }
861 }
862 uint8_t ii;
863 uint8_t clkCnt, tol = 0;
864 uint16_t bestErr[]={1000,1000,1000,1000,1000,1000,1000,1000,1000};
865 uint8_t bestStart[]={0,0,0,0,0,0,0,0,0};
866 size_t errCnt = 0;
867 size_t arrLoc, loopEnd;
868
869 if (clockFnd>0) {
870 clkCnt = clockFnd;
871 clkEnd = clockFnd+1;
872 }
873 else clkCnt=1;
874
875 //test each valid clock from smallest to greatest to see which lines up
876 for(; clkCnt < clkEnd; clkCnt++){
877 if (clk[clkCnt] <= 32){
878 tol=1;
879 }else{
880 tol=0;
881 }
882 //if no errors allowed - keep start within the first clock
883 if (!maxErr && size > clk[clkCnt]*2 + tol && clk[clkCnt]<128) loopCnt=clk[clkCnt]*2;
884 bestErr[clkCnt]=1000;
885 //try lining up the peaks by moving starting point (try first few clocks)
886 for (ii=0; ii < loopCnt; ii++){
887 if (dest[ii] < peak && dest[ii] > low) continue;
888
889 errCnt=0;
890 // now that we have the first one lined up test rest of wave array
891 loopEnd = ((size-ii-tol) / clk[clkCnt]) - 1;
892 for (i=0; i < loopEnd; ++i){
893 arrLoc = ii + (i * clk[clkCnt]);
894 if (dest[arrLoc] >= peak || dest[arrLoc] <= low){
895 }else if (dest[arrLoc-tol] >= peak || dest[arrLoc-tol] <= low){
896 }else if (dest[arrLoc+tol] >= peak || dest[arrLoc+tol] <= low){
897 }else{ //error no peak detected
898 errCnt++;
899 }
900 }
901 //if we found no errors then we can stop here and a low clock (common clocks)
902 // this is correct one - return this clock
903 if (g_debugMode == 2) prnt("DEBUG ASK: clk %d, err %d, startpos %d, endpos %d",clk[clkCnt],errCnt,ii,i);
904 if(errCnt==0 && clkCnt<7) {
905 if (!clockFnd) *clock = clk[clkCnt];
906 return ii;
907 }
908 //if we found errors see if it is lowest so far and save it as best run
909 if(errCnt<bestErr[clkCnt]){
910 bestErr[clkCnt]=errCnt;
911 bestStart[clkCnt]=ii;
912 }
913 }
914 }
915 uint8_t iii;
916 uint8_t best=0;
917 for (iii=1; iii<clkEnd; ++iii){
918 if (bestErr[iii] < bestErr[best]){
919 if (bestErr[iii] == 0) bestErr[iii]=1;
920 // current best bit to error ratio vs new bit to error ratio
921 if ( (size/clk[best])/bestErr[best] < (size/clk[iii])/bestErr[iii] ){
922 best = iii;
923 }
924 }
925 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]);
926 }
927 if (!clockFnd) *clock = clk[best];
928 return bestStart[best];
929 }
930
931 //by marshmellow
932 //detect psk clock by reading each phase shift
933 // a phase shift is determined by measuring the sample length of each wave
934 int DetectPSKClock(uint8_t dest[], size_t size, int clock)
935 {
936 uint8_t clk[]={255,16,32,40,50,64,100,128,255}; //255 is not a valid clock
937 uint16_t loopCnt = 4096; //don't need to loop through entire array...
938 if (size == 0) return 0;
939 if (size<loopCnt) loopCnt = size-20;
940
941 //if we already have a valid clock quit
942 size_t i=1;
943 for (; i < 8; ++i)
944 if (clk[i] == clock) return clock;
945
946 size_t waveStart=0, waveEnd=0, firstFullWave=0, lastClkBit=0;
947 uint8_t clkCnt, fc=0, fullWaveLen=0, tol=1;
948 uint16_t peakcnt=0, errCnt=0, waveLenCnt=0;
949 uint16_t bestErr[]={1000,1000,1000,1000,1000,1000,1000,1000,1000};
950 uint16_t peaksdet[]={0,0,0,0,0,0,0,0,0};
951 fc = countFC(dest, size, 0);
952 if (fc!=2 && fc!=4 && fc!=8) return -1;
953 if (g_debugMode==2) prnt("DEBUG PSK: FC: %d",fc);
954
955 //find first full wave
956 for (i=160; i<loopCnt; i++){
957 if (dest[i] < dest[i+1] && dest[i+1] >= dest[i+2]){
958 if (waveStart == 0) {
959 waveStart = i+1;
960 //prnt("DEBUG: waveStart: %d",waveStart);
961 } else {
962 waveEnd = i+1;
963 //prnt("DEBUG: waveEnd: %d",waveEnd);
964 waveLenCnt = waveEnd-waveStart;
965 if (waveLenCnt > fc){
966 firstFullWave = waveStart;
967 fullWaveLen=waveLenCnt;
968 break;
969 }
970 waveStart=0;
971 }
972 }
973 }
974 if (g_debugMode ==2) prnt("DEBUG PSK: firstFullWave: %d, waveLen: %d",firstFullWave,fullWaveLen);
975
976 //test each valid clock from greatest to smallest to see which lines up
977 for(clkCnt=7; clkCnt >= 1 ; clkCnt--){
978 lastClkBit = firstFullWave; //set end of wave as clock align
979 waveStart = 0;
980 errCnt=0;
981 peakcnt=0;
982 if (g_debugMode == 2) prnt("DEBUG PSK: clk: %d, lastClkBit: %d",clk[clkCnt],lastClkBit);
983
984 for (i = firstFullWave+fullWaveLen-1; i < loopCnt-2; i++){
985 //top edge of wave = start of new wave
986 if (dest[i] < dest[i+1] && dest[i+1] >= dest[i+2]){
987 if (waveStart == 0) {
988 waveStart = i+1;
989 waveLenCnt=0;
990 } else { //waveEnd
991 waveEnd = i+1;
992 waveLenCnt = waveEnd-waveStart;
993 if (waveLenCnt > fc){
994 //if this wave is a phase shift
995 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);
996 if (i+1 >= lastClkBit + clk[clkCnt] - tol){ //should be a clock bit
997 peakcnt++;
998 lastClkBit+=clk[clkCnt];
999 } else if (i<lastClkBit+8){
1000 //noise after a phase shift - ignore
1001 } else { //phase shift before supposed to based on clock
1002 errCnt++;
1003 }
1004 } else if (i+1 > lastClkBit + clk[clkCnt] + tol + fc){
1005 lastClkBit+=clk[clkCnt]; //no phase shift but clock bit
1006 }
1007 waveStart=i+1;
1008 }
1009 }
1010 }
1011 if (errCnt == 0){
1012 return clk[clkCnt];
1013 }
1014 if (errCnt <= bestErr[clkCnt]) bestErr[clkCnt]=errCnt;
1015 if (peakcnt > peaksdet[clkCnt]) peaksdet[clkCnt]=peakcnt;
1016 }
1017 //all tested with errors
1018 //return the highest clk with the most peaks found
1019 uint8_t best=7;
1020 for (i=7; i>=1; i--){
1021 if (peaksdet[i] > peaksdet[best]) {
1022 best = i;
1023 }
1024 if (g_debugMode == 2) prnt("DEBUG PSK: Clk: %d, peaks: %d, errs: %d, bestClk: %d",clk[i],peaksdet[i],bestErr[i],clk[best]);
1025 }
1026 return clk[best];
1027 }
1028
1029 int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low){
1030 //find shortest transition from high to low
1031 size_t i = 0;
1032 size_t transition1 = 0;
1033 int lowestTransition = 255;
1034 bool lastWasHigh = false;
1035
1036 //find first valid beginning of a high or low wave
1037 while ((dest[i] >= peak || dest[i] <= low) && (i < size))
1038 ++i;
1039 while ((dest[i] < peak && dest[i] > low) && (i < size))
1040 ++i;
1041 lastWasHigh = (dest[i] >= peak);
1042
1043 if (i==size) return 0;
1044 transition1 = i;
1045
1046 for (;i < size; i++) {
1047 if ((dest[i] >= peak && !lastWasHigh) || (dest[i] <= low && lastWasHigh)) {
1048 lastWasHigh = (dest[i] >= peak);
1049 if (i-transition1 < lowestTransition) lowestTransition = i-transition1;
1050 transition1 = i;
1051 }
1052 }
1053 if (lowestTransition == 255) lowestTransition = 0;
1054 if (g_debugMode==2) prnt("DEBUG NRZ: detectstrongNRZclk smallest wave: %d",lowestTransition);
1055 return lowestTransition;
1056 }
1057
1058 //by marshmellow
1059 //detect nrz clock by reading #peaks vs no peaks(or errors)
1060 int DetectNRZClock(uint8_t dest[], size_t size, int clock)
1061 {
1062 size_t i=0;
1063 uint8_t clk[]={8,16,32,40,50,64,100,128,255};
1064 size_t loopCnt = 4096; //don't need to loop through entire array...
1065 if (size == 0) return 0;
1066 if (size<loopCnt) loopCnt = size-20;
1067 //if we already have a valid clock quit
1068 for (; i < 8; ++i)
1069 if (clk[i] == clock) return clock;
1070
1071 //get high and low peak
1072 int peak, low;
1073 if (getHiLo(dest, loopCnt, &peak, &low, 75, 75) < 1) return 0;
1074
1075 int lowestTransition = DetectStrongNRZClk(dest, size-20, peak, low);
1076 size_t ii;
1077 uint8_t clkCnt;
1078 uint8_t tol = 0;
1079 uint16_t smplCnt = 0;
1080 int16_t peakcnt = 0;
1081 int16_t peaksdet[] = {0,0,0,0,0,0,0,0};
1082 uint16_t maxPeak = 255;
1083 bool firstpeak = false;
1084 //test for large clipped waves
1085 for (i=0; i<loopCnt; i++){
1086 if (dest[i] >= peak || dest[i] <= low){
1087 if (!firstpeak) continue;
1088 smplCnt++;
1089 } else {
1090 firstpeak=true;
1091 if (smplCnt > 6 ){
1092 if (maxPeak > smplCnt){
1093 maxPeak = smplCnt;
1094 //prnt("maxPk: %d",maxPeak);
1095 }
1096 peakcnt++;
1097 //prnt("maxPk: %d, smplCnt: %d, peakcnt: %d",maxPeak,smplCnt,peakcnt);
1098 smplCnt=0;
1099 }
1100 }
1101 }
1102 bool errBitHigh = 0;
1103 bool bitHigh = 0;
1104 uint8_t ignoreCnt = 0;
1105 uint8_t ignoreWindow = 4;
1106 bool lastPeakHigh = 0;
1107 int lastBit = 0;
1108 peakcnt=0;
1109 //test each valid clock from smallest to greatest to see which lines up
1110 for(clkCnt=0; clkCnt < 8; ++clkCnt){
1111 //ignore clocks smaller than smallest peak
1112 if (clk[clkCnt] < maxPeak - (clk[clkCnt]/4)) continue;
1113 //try lining up the peaks by moving starting point (try first 256)
1114 for (ii=20; ii < loopCnt; ++ii){
1115 if ((dest[ii] >= peak) || (dest[ii] <= low)){
1116 peakcnt = 0;
1117 bitHigh = false;
1118 ignoreCnt = 0;
1119 lastBit = ii-clk[clkCnt];
1120 //loop through to see if this start location works
1121 for (i = ii; i < size-20; ++i) {
1122 //if we are at a clock bit
1123 if ((i >= lastBit + clk[clkCnt] - tol) && (i <= lastBit + clk[clkCnt] + tol)) {
1124 //test high/low
1125 if (dest[i] >= peak || dest[i] <= low) {
1126 //if same peak don't count it
1127 if ((dest[i] >= peak && !lastPeakHigh) || (dest[i] <= low && lastPeakHigh)) {
1128 peakcnt++;
1129 }
1130 lastPeakHigh = (dest[i] >= peak);
1131 bitHigh = true;
1132 errBitHigh = false;
1133 ignoreCnt = ignoreWindow;
1134 lastBit += clk[clkCnt];
1135 } else if (i == lastBit + clk[clkCnt] + tol) {
1136 lastBit += clk[clkCnt];
1137 }
1138 //else if not a clock bit and no peaks
1139 } else if (dest[i] < peak && dest[i] > low){
1140 if (ignoreCnt==0){
1141 bitHigh=false;
1142 if (errBitHigh==true) peakcnt--;
1143 errBitHigh=false;
1144 } else {
1145 ignoreCnt--;
1146 }
1147 // else if not a clock bit but we have a peak
1148 } else if ((dest[i]>=peak || dest[i]<=low) && (!bitHigh)) {
1149 //error bar found no clock...
1150 errBitHigh=true;
1151 }
1152 }
1153 if(peakcnt>peaksdet[clkCnt]) {
1154 peaksdet[clkCnt]=peakcnt;
1155 }
1156 }
1157 }
1158 }
1159 int iii=7;
1160 uint8_t best=0;
1161 for (iii=7; iii > 0; iii--){
1162 if ((peaksdet[iii] >= (peaksdet[best]-1)) && (peaksdet[iii] <= peaksdet[best]+1) && lowestTransition) {
1163 if (clk[iii] > (lowestTransition - (clk[iii]/8)) && clk[iii] < (lowestTransition + (clk[iii]/8))) {
1164 best = iii;
1165 }
1166 } else if (peaksdet[iii] > peaksdet[best]){
1167 best = iii;
1168 }
1169 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);
1170 }
1171
1172 return clk[best];
1173 }
1174
1175 // by marshmellow
1176 // convert psk1 demod to psk2 demod
1177 // only transition waves are 1s
1178 void psk1TOpsk2(uint8_t *BitStream, size_t size)
1179 {
1180 size_t i=1;
1181 uint8_t lastBit=BitStream[0];
1182 for (; i<size; i++){
1183 if (BitStream[i]==7){
1184 //ignore errors
1185 } else if (lastBit!=BitStream[i]){
1186 lastBit=BitStream[i];
1187 BitStream[i]=1;
1188 } else {
1189 BitStream[i]=0;
1190 }
1191 }
1192 return;
1193 }
1194
1195 // by marshmellow
1196 // convert psk2 demod to psk1 demod
1197 // from only transition waves are 1s to phase shifts change bit
1198 void psk2TOpsk1(uint8_t *BitStream, size_t size)
1199 {
1200 uint8_t phase=0;
1201 for (size_t i=0; i<size; i++){
1202 if (BitStream[i]==1){
1203 phase ^=1;
1204 }
1205 BitStream[i]=phase;
1206 }
1207 return;
1208 }
1209
1210 // redesigned by marshmellow adjusted from existing decode functions
1211 // indala id decoding - only tested on 26 bit tags, but attempted to make it work for more
1212 int indala26decode(uint8_t *bitStream, size_t *size, uint8_t *invert)
1213 {
1214 //26 bit 40134 format (don't know other formats)
1215 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};
1216 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};
1217 size_t startidx = 0;
1218 if (!preambleSearch(bitStream, preamble, sizeof(preamble), size, &startidx)){
1219 // if didn't find preamble try again inverting
1220 if (!preambleSearch(bitStream, preamble_i, sizeof(preamble_i), size, &startidx)) return -1;
1221 *invert ^= 1;
1222 }
1223 if (*size != 64 && *size != 224) return -2;
1224 if (*invert==1)
1225 for (size_t i = startidx; i < *size; i++)
1226 bitStream[i] ^= 1;
1227
1228 return (int) startidx;
1229 }
1230
1231 // by marshmellow - demodulate NRZ wave - requires a read with strong signal
1232 // peaks invert bit (high=1 low=0) each clock cycle = 1 bit determined by last peak
1233 int nrzRawDemod(uint8_t *dest, size_t *size, int *clk, int *invert){
1234 if (justNoise(dest, *size)) return -1;
1235 *clk = DetectNRZClock(dest, *size, *clk);
1236 if (*clk==0) return -2;
1237 size_t i, gLen = 4096;
1238 if (gLen>*size) gLen = *size-20;
1239 int high, low;
1240 if (getHiLo(dest, gLen, &high, &low, 75, 75) < 1) return -3; //25% fuzz on high 25% fuzz on low
1241
1242 uint8_t bit=0;
1243 //convert wave samples to 1's and 0's
1244 for(i=20; i < *size-20; i++){
1245 if (dest[i] >= high) bit = 1;
1246 if (dest[i] <= low) bit = 0;
1247 dest[i] = bit;
1248 }
1249 //now demod based on clock (rf/32 = 32 1's for one 1 bit, 32 0's for one 0 bit)
1250 size_t lastBit = 0;
1251 size_t numBits = 0;
1252 for(i=21; i < *size-20; i++) {
1253 //if transition detected or large number of same bits - store the passed bits
1254 if (dest[i] != dest[i-1] || (i-lastBit) == (10 * *clk)) {
1255 memset(dest+numBits, dest[i-1] ^ *invert, (i - lastBit + (*clk/4)) / *clk);
1256 numBits += (i - lastBit + (*clk/4)) / *clk;
1257 lastBit = i-1;
1258 }
1259 }
1260 *size = numBits;
1261 return 0;
1262 }
1263
1264 //by marshmellow
1265 //detects the bit clock for FSK given the high and low Field Clocks
1266 uint8_t detectFSKClk(uint8_t *BitStream, size_t size, uint8_t fcHigh, uint8_t fcLow)
1267 {
1268 uint8_t clk[] = {8,16,32,40,50,64,100,128,0};
1269 uint16_t rfLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1270 uint8_t rfCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1271 uint8_t rfLensFnd = 0;
1272 uint8_t lastFCcnt = 0;
1273 uint16_t fcCounter = 0;
1274 uint16_t rfCounter = 0;
1275 uint8_t firstBitFnd = 0;
1276 size_t i;
1277 if (size == 0) return 0;
1278
1279 uint8_t fcTol = ((fcHigh*100 - fcLow*100)/2 + 50)/100; //(uint8_t)(0.5+(float)(fcHigh-fcLow)/2);
1280 rfLensFnd=0;
1281 fcCounter=0;
1282 rfCounter=0;
1283 firstBitFnd=0;
1284 //PrintAndLog("DEBUG: fcTol: %d",fcTol);
1285 // prime i to first peak / up transition
1286 for (i = 160; i < size-20; i++)
1287 if (BitStream[i] > BitStream[i-1] && BitStream[i]>=BitStream[i+1])
1288 break;
1289
1290 for (; i < size-20; i++){
1291 fcCounter++;
1292 rfCounter++;
1293
1294 if (BitStream[i] <= BitStream[i-1] || BitStream[i] < BitStream[i+1])
1295 continue;
1296 // else new peak
1297 // if we got less than the small fc + tolerance then set it to the small fc
1298 if (fcCounter < fcLow+fcTol)
1299 fcCounter = fcLow;
1300 else //set it to the large fc
1301 fcCounter = fcHigh;
1302
1303 //look for bit clock (rf/xx)
1304 if ((fcCounter < lastFCcnt || fcCounter > lastFCcnt)){
1305 //not the same size as the last wave - start of new bit sequence
1306 if (firstBitFnd > 1){ //skip first wave change - probably not a complete bit
1307 for (int ii=0; ii<15; ii++){
1308 if (rfLens[ii] >= (rfCounter-4) && rfLens[ii] <= (rfCounter+4)){
1309 rfCnts[ii]++;
1310 rfCounter = 0;
1311 break;
1312 }
1313 }
1314 if (rfCounter > 0 && rfLensFnd < 15){
1315 //PrintAndLog("DEBUG: rfCntr %d, fcCntr %d",rfCounter,fcCounter);
1316 rfCnts[rfLensFnd]++;
1317 rfLens[rfLensFnd++] = rfCounter;
1318 }
1319 } else {
1320 firstBitFnd++;
1321 }
1322 rfCounter=0;
1323 lastFCcnt=fcCounter;
1324 }
1325 fcCounter=0;
1326 }
1327 uint8_t rfHighest=15, rfHighest2=15, rfHighest3=15;
1328
1329 for (i=0; i<15; i++){
1330 //get highest 2 RF values (might need to get more values to compare or compare all?)
1331 if (rfCnts[i]>rfCnts[rfHighest]){
1332 rfHighest3=rfHighest2;
1333 rfHighest2=rfHighest;
1334 rfHighest=i;
1335 } else if(rfCnts[i]>rfCnts[rfHighest2]){
1336 rfHighest3=rfHighest2;
1337 rfHighest2=i;
1338 } else if(rfCnts[i]>rfCnts[rfHighest3]){
1339 rfHighest3=i;
1340 }
1341 if (g_debugMode==2) prnt("DEBUG FSK: RF %d, cnts %d",rfLens[i], rfCnts[i]);
1342 }
1343 // set allowed clock remainder tolerance to be 1 large field clock length+1
1344 // we could have mistakenly made a 9 a 10 instead of an 8 or visa versa so rfLens could be 1 FC off
1345 uint8_t tol1 = fcHigh+1;
1346
1347 if (g_debugMode==2) prnt("DEBUG FSK: most counted rf values: 1 %d, 2 %d, 3 %d",rfLens[rfHighest],rfLens[rfHighest2],rfLens[rfHighest3]);
1348
1349 // loop to find the highest clock that has a remainder less than the tolerance
1350 // compare samples counted divided by
1351 // test 128 down to 32 (shouldn't be possible to have fc/10 & fc/8 and rf/16 or less)
1352 int ii=7;
1353 for (; ii>=2; ii--){
1354 if (rfLens[rfHighest] % clk[ii] < tol1 || rfLens[rfHighest] % clk[ii] > clk[ii]-tol1){
1355 if (rfLens[rfHighest2] % clk[ii] < tol1 || rfLens[rfHighest2] % clk[ii] > clk[ii]-tol1){
1356 if (rfLens[rfHighest3] % clk[ii] < tol1 || rfLens[rfHighest3] % clk[ii] > clk[ii]-tol1){
1357 if (g_debugMode==2) prnt("DEBUG FSK: clk %d divides into the 3 most rf values within tolerance",clk[ii]);
1358 break;
1359 }
1360 }
1361 }
1362 }
1363
1364 if (ii<0) return 0; // oops we went too far
1365
1366 return clk[ii];
1367 }
1368
1369 //by marshmellow
1370 //countFC is to detect the field clock lengths.
1371 //counts and returns the 2 most common wave lengths
1372 //mainly used for FSK field clock detection
1373 uint16_t countFC(uint8_t *BitStream, size_t size, uint8_t fskAdj)
1374 {
1375 uint8_t fcLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1376 uint16_t fcCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
1377 uint8_t fcLensFnd = 0;
1378 uint8_t lastFCcnt = 0;
1379 uint8_t fcCounter = 0;
1380 size_t i;
1381 if (size < 180) return 0;
1382
1383 // prime i to first up transition
1384 for (i = 160; i < size-20; i++)
1385 if (BitStream[i] > BitStream[i-1] && BitStream[i] >= BitStream[i+1])
1386 break;
1387
1388 for (; i < size-20; i++){
1389 if (BitStream[i] > BitStream[i-1] && BitStream[i] >= BitStream[i+1]){
1390 // new up transition
1391 fcCounter++;
1392 if (fskAdj){
1393 //if we had 5 and now have 9 then go back to 8 (for when we get a fc 9 instead of an 8)
1394 if (lastFCcnt==5 && fcCounter==9) fcCounter--;
1395 //if fc=9 or 4 add one (for when we get a fc 9 instead of 10 or a 4 instead of a 5)
1396 if ((fcCounter==9) || fcCounter==4) fcCounter++;
1397 // save last field clock count (fc/xx)
1398 lastFCcnt = fcCounter;
1399 }
1400 // find which fcLens to save it to:
1401 for (int ii=0; ii<15; ii++){
1402 if (fcLens[ii]==fcCounter){
1403 fcCnts[ii]++;
1404 fcCounter=0;
1405 break;
1406 }
1407 }
1408 if (fcCounter>0 && fcLensFnd<15){
1409 //add new fc length
1410 fcCnts[fcLensFnd]++;
1411 fcLens[fcLensFnd++]=fcCounter;
1412 }
1413 fcCounter=0;
1414 } else {
1415 // count sample
1416 fcCounter++;
1417 }
1418 }
1419
1420 uint8_t best1=14, best2=14, best3=14;
1421 uint16_t maxCnt1=0;
1422 // go through fclens and find which ones are bigest 2
1423 for (i=0; i<15; i++){
1424 // get the 3 best FC values
1425 if (fcCnts[i]>maxCnt1) {
1426 best3=best2;
1427 best2=best1;
1428 maxCnt1=fcCnts[i];
1429 best1=i;
1430 } else if(fcCnts[i]>fcCnts[best2]){
1431 best3=best2;
1432 best2=i;
1433 } else if(fcCnts[i]>fcCnts[best3]){
1434 best3=i;
1435 }
1436 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]);
1437 }
1438 if (fcLens[best1]==0) return 0;
1439 uint8_t fcH=0, fcL=0;
1440 if (fcLens[best1]>fcLens[best2]){
1441 fcH=fcLens[best1];
1442 fcL=fcLens[best2];
1443 } else{
1444 fcH=fcLens[best2];
1445 fcL=fcLens[best1];
1446 }
1447 if ((size-180)/fcH/3 > fcCnts[best1]+fcCnts[best2]) {
1448 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]);
1449 return 0; //lots of waves not psk or fsk
1450 }
1451 // TODO: take top 3 answers and compare to known Field clocks to get top 2
1452
1453 uint16_t fcs = (((uint16_t)fcH)<<8) | fcL;
1454 if (fskAdj) return fcs;
1455 return fcLens[best1];
1456 }
1457
1458 //by marshmellow - demodulate PSK1 wave
1459 //uses wave lengths (# Samples)
1460 int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert)
1461 {
1462 if (size == 0) return -1;
1463 uint16_t loopCnt = 4096; //don't need to loop through entire array...
1464 if (*size<loopCnt) loopCnt = *size;
1465
1466 size_t numBits=0;
1467 uint8_t curPhase = *invert;
1468 size_t i, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0;
1469 uint8_t fc=0, fullWaveLen=0, tol=1;
1470 uint16_t errCnt=0, waveLenCnt=0;
1471 fc = countFC(dest, *size, 0);
1472 if (fc!=2 && fc!=4 && fc!=8) return -1;
1473 //PrintAndLog("DEBUG: FC: %d",fc);
1474 *clock = DetectPSKClock(dest, *size, *clock);
1475 if (*clock == 0) return -1;
1476 int avgWaveVal=0, lastAvgWaveVal=0;
1477 //find first phase shift
1478 for (i=0; i<loopCnt; i++){
1479 if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
1480 waveEnd = i+1;
1481 //PrintAndLog("DEBUG: waveEnd: %d",waveEnd);
1482 waveLenCnt = waveEnd-waveStart;
1483 if (waveLenCnt > fc && waveStart > fc && !(waveLenCnt > fc+2)){ //not first peak and is a large wave but not out of whack
1484 lastAvgWaveVal = avgWaveVal/(waveLenCnt);
1485 firstFullWave = waveStart;
1486 fullWaveLen=waveLenCnt;
1487 //if average wave value is > graph 0 then it is an up wave or a 1
1488 if (lastAvgWaveVal > 123) curPhase ^= 1; //fudge graph 0 a little 123 vs 128
1489 break;
1490 }
1491 waveStart = i+1;
1492 avgWaveVal = 0;
1493 }
1494 avgWaveVal += dest[i+2];
1495 }
1496 if (firstFullWave == 0) {
1497 // no phase shift detected - could be all 1's or 0's - doesn't matter where we start
1498 // so skip a little to ensure we are past any Start Signal
1499 firstFullWave = 160;
1500 memset(dest, curPhase, firstFullWave / *clock);
1501 } else {
1502 memset(dest, curPhase^1, firstFullWave / *clock);
1503 }
1504 //advance bits
1505 numBits += (firstFullWave / *clock);
1506 //set start of wave as clock align
1507 lastClkBit = firstFullWave;
1508 if (g_debugMode==2) prnt("DEBUG PSK: firstFullWave: %u, waveLen: %u",firstFullWave,fullWaveLen);
1509 if (g_debugMode==2) prnt("DEBUG: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit,(unsigned int) fc);
1510 waveStart = 0;
1511 dest[numBits++] = curPhase; //set first read bit
1512 for (i = firstFullWave + fullWaveLen - 1; i < *size-3; i++){
1513 //top edge of wave = start of new wave
1514 if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){
1515 if (waveStart == 0) {
1516 waveStart = i+1;
1517 waveLenCnt = 0;
1518 avgWaveVal = dest[i+1];
1519 } else { //waveEnd
1520 waveEnd = i+1;
1521 waveLenCnt = waveEnd-waveStart;
1522 lastAvgWaveVal = avgWaveVal/waveLenCnt;
1523 if (waveLenCnt > fc){
1524 //PrintAndLog("DEBUG: avgWaveVal: %d, waveSum: %d",lastAvgWaveVal,avgWaveVal);
1525 //this wave is a phase shift
1526 //PrintAndLog("DEBUG: phase shift at: %d, len: %d, nextClk: %d, i: %d, fc: %d",waveStart,waveLenCnt,lastClkBit+*clock-tol,i+1,fc);
1527 if (i+1 >= lastClkBit + *clock - tol){ //should be a clock bit
1528 curPhase ^= 1;
1529 dest[numBits++] = curPhase;
1530 lastClkBit += *clock;
1531 } else if (i < lastClkBit+10+fc){
1532 //noise after a phase shift - ignore
1533 } else { //phase shift before supposed to based on clock
1534 errCnt++;
1535 dest[numBits++] = 7;
1536 }
1537 } else if (i+1 > lastClkBit + *clock + tol + fc){
1538 lastClkBit += *clock; //no phase shift but clock bit
1539 dest[numBits++] = curPhase;
1540 }
1541 avgWaveVal = 0;
1542 waveStart = i+1;
1543 }
1544 }
1545 avgWaveVal += dest[i+1];
1546 }
1547 *size = numBits;
1548 return errCnt;
1549 }
1550
1551 //by marshmellow
1552 //attempt to identify a Sequence Terminator in ASK modulated raw wave
1553 bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
1554 size_t bufsize = *size;
1555 //need to loop through all samples and identify our clock, look for the ST pattern
1556 uint8_t fndClk[] = {8,16,32,40,50,64,128};
1557 int clk = 0;
1558 int tol = 0;
1559 int i, j, skip, start, end, low, high, minClk, waveStart;
1560 bool complete = false;
1561 int tmpbuff[bufsize / 32]; //guess rf/32 clock, if click is smaller we will only have room for a fraction of the samples captured
1562 int waveLen[bufsize / 32]; // if clock is larger then we waste memory in array size that is not needed...
1563 size_t testsize = (bufsize < 512) ? bufsize : 512;
1564 int phaseoff = 0;
1565 high = low = 128;
1566 memset(tmpbuff, 0, sizeof(tmpbuff));
1567
1568 if ( getHiLo(buffer, testsize, &high, &low, 80, 80) == -1 ) {
1569 if (g_debugMode==2) prnt("DEBUG STT: just noise detected - quitting");
1570 return false; //just noise
1571 }
1572 i = 0;
1573 j = 0;
1574 minClk = 255;
1575 // get to first full low to prime loop and skip incomplete first pulse
1576 while ((buffer[i] < high) && (i < bufsize))
1577 ++i;
1578 while ((buffer[i] > low) && (i < bufsize))
1579 ++i;
1580 skip = i;
1581
1582 // populate tmpbuff buffer with pulse lengths
1583 while (i < bufsize) {
1584 // measure from low to low
1585 while ((buffer[i] > low) && (i < bufsize))
1586 ++i;
1587 start= i;
1588 while ((buffer[i] < high) && (i < bufsize))
1589 ++i;
1590 //first high point for this wave
1591 waveStart = i;
1592 while ((buffer[i] > low) && (i < bufsize))
1593 ++i;
1594 if (j >= (bufsize/32)) {
1595 break;
1596 }
1597 waveLen[j] = i - waveStart; //first high to first low
1598 tmpbuff[j++] = i - start;
1599 if (i-start < minClk && i < bufsize) {
1600 minClk = i - start;
1601 }
1602 }
1603 // set clock - might be able to get this externally and remove this work...
1604 if (!clk) {
1605 for (uint8_t clkCnt = 0; clkCnt<7; clkCnt++) {
1606 tol = fndClk[clkCnt]/8;
1607 if (minClk >= fndClk[clkCnt]-tol && minClk <= fndClk[clkCnt]+1) {
1608 clk=fndClk[clkCnt];
1609 break;
1610 }
1611 }
1612 // clock not found - ERROR
1613 if (!clk) {
1614 if (g_debugMode==2) prnt("DEBUG STT: clock not found - quitting");
1615 return false;
1616 }
1617 } else tol = clk/8;
1618
1619 *foundclock = clk;
1620
1621 // look for Sequence Terminator - should be pulses of clk*(1 or 1.5), clk*2, clk*(1.5 or 2)
1622 start = -1;
1623 for (i = 0; i < j - 4; ++i) {
1624 skip += tmpbuff[i];
1625 if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior
1626 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
1627 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
1628 if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
1629 start = i + 3;
1630 break;
1631 }
1632 }
1633 }
1634 }
1635 }
1636 // first ST not found - ERROR
1637 if (start < 0) {
1638 if (g_debugMode==2) prnt("DEBUG STT: first STT not found - quitting");
1639 return false;
1640 } else {
1641 if (g_debugMode==2) prnt("DEBUG STT: first STT found at: %d, j=%d",start, j);
1642 }
1643 if (waveLen[i+2] > clk*1+tol)
1644 phaseoff = 0;
1645 else
1646 phaseoff = clk/2;
1647
1648 // skip over the remainder of ST
1649 skip += clk*7/2; //3.5 clocks from tmpbuff[i] = end of st - also aligns for ending point
1650
1651 // now do it again to find the end
1652 end = skip;
1653 for (i += 3; i < j - 4; ++i) {
1654 end += tmpbuff[i];
1655 if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior
1656 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
1657 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
1658 if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
1659 complete = true;
1660 break;
1661 }
1662 }
1663 }
1664 }
1665 }
1666 end -= phaseoff;
1667 //didn't find second ST - ERROR
1668 if (!complete) {
1669 if (g_debugMode==2) prnt("DEBUG STT: second STT not found - quitting");
1670 return false;
1671 }
1672 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);
1673 //now begin to trim out ST so we can use normal demod cmds
1674 start = skip;
1675 size_t datalen = end - start;
1676 // check validity of datalen (should be even clock increments) - use a tolerance of up to 1/8th a clock
1677 if ( clk - (datalen % clk) <= clk/8) {
1678 // padd the amount off - could be problematic... but shouldn't happen often
1679 datalen += clk - (datalen % clk);
1680 } else if ( (datalen % clk) <= clk/8 ) {
1681 // padd the amount off - could be problematic... but shouldn't happen often
1682 datalen -= datalen % clk;
1683 } else {
1684 if (g_debugMode==2) prnt("DEBUG STT: datalen not divisible by clk: %u %% %d = %d - quitting", datalen, clk, datalen % clk);
1685 return false;
1686 }
1687 // if datalen is less than one t55xx block - ERROR
1688 if (datalen/clk < 8*4) {
1689 if (g_debugMode==2) prnt("DEBUG STT: datalen is less than 1 full t55xx block - quitting");
1690 return false;
1691 }
1692 size_t dataloc = start;
1693 if (buffer[dataloc-(clk*4)-(clk/8)] <= low && buffer[dataloc] <= low && buffer[dataloc-(clk*4)] >= high) {
1694 //we have low drift (and a low just before the ST and a low just after the ST) - compensate by backing up the start
1695 for ( i=0; i <= (clk/8); ++i ) {
1696 if ( buffer[dataloc - (clk*4) - i] <= low ) {
1697 dataloc -= i;
1698 break;
1699 }
1700 }
1701 }
1702
1703 size_t newloc = 0;
1704 i=0;
1705 if (g_debugMode==2) prnt("DEBUG STT: Starting STT trim - start: %d, datalen: %d ",dataloc, datalen);
1706
1707 // warning - overwriting buffer given with raw wave data with ST removed...
1708 while ( dataloc < bufsize-(clk/2) ) {
1709 //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)
1710 if (buffer[dataloc]<high && buffer[dataloc]>low && buffer[dataloc+3]<high && buffer[dataloc+3]>low) {
1711 for(i=0; i < clk/2-tol; ++i) {
1712 buffer[dataloc+i] = high+5;
1713 }
1714 }
1715 for (i=0; i<datalen; ++i) {
1716 if (i+newloc < bufsize) {
1717 if (i+newloc < dataloc)
1718 buffer[i+newloc] = buffer[dataloc];
1719
1720 dataloc++;
1721 }
1722 }
1723 newloc += i;
1724 //skip next ST - we just assume it will be there from now on...
1725 if (g_debugMode==2) prnt("DEBUG STT: skipping STT at %d to %d", dataloc, dataloc+(clk*4));
1726 dataloc += clk*4;
1727 }
1728 *size = newloc;
1729 return true;
1730 }
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