common/lfdemod.c

   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 commands
   9 //-----------------------------------------------------------------------------
  10
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include "lfdemod.h"
  14
  15 //by marshmellow
  16 //takes 1s and 0s and searches for EM410x format - output EM ID
  17 uint64_t Em410xDecode(uint8_t *BitStream,uint32_t BitLen)
  18 {
  19     //no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
  20     //  otherwise could be a void with no arguments
  21     //set defaults
  22     int high=0, low=128;
  23     uint64_t lo=0; //hi=0,
  24
  25     uint32_t i = 0;
  26     uint32_t initLoopMax = 65;
  27     if (initLoopMax>BitLen) initLoopMax=BitLen;
  28
  29     for (;i < initLoopMax; ++i) //65 samples should be plenty to find high and low values
  30     {
  31         if (BitStream[i] > high)
  32             high = BitStream[i];
  33         else if (BitStream[i] < low)
  34             low = BitStream[i];
  35     }
  36     if (((high !=1)||(low !=0))){  //allow only 1s and 0s
  37         // PrintAndLog("no data found");
  38         return 0;
  39     }
  40     uint8_t parityTest=0;
  41     // 111111111 bit pattern represent start of frame
  42     uint8_t frame_marker_mask[] = {1,1,1,1,1,1,1,1,1};
  43     uint32_t idx = 0;
  44     uint32_t ii=0;
  45     uint8_t resetCnt = 0;
  46     while( (idx + 64) < BitLen) {
  47 restart:
  48         // search for a start of frame marker
  49         if ( memcmp(BitStream+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
  50         { // frame marker found
  51             idx+=9;//sizeof(frame_marker_mask);
  52             for (i=0; i<10;i++){
  53                 for(ii=0; ii<5; ++ii){
  54                     parityTest += BitStream[(i*5)+ii+idx];
  55                 }
  56                 if (parityTest== ((parityTest>>1)<<1)){
  57                     parityTest=0;
  58                     for (ii=0; ii<4;++ii){
  59                         //hi = (hi<<1)|(lo>>31);
  60                         lo=(lo<<1LL)|(BitStream[(i*5)+ii+idx]);
  61                     }
  62                     //PrintAndLog("DEBUG: EM parity passed parity val: %d, i:%d, ii:%d,idx:%d, Buffer: %d%d%d%d%d,lo: %d",parityTest,i,ii,idx,BitStream[idx+ii+(i*5)-5],BitStream[idx+ii+(i*5)-4],BitStream[idx+ii+(i*5)-3],BitStream[idx+ii+(i*5)-2],BitStream[idx+ii+(i*5)-1],lo);
  63                 }else {//parity failed
  64                     //PrintAndLog("DEBUG: EM parity failed parity val: %d, i:%d, ii:%d,idx:%d, Buffer: %d%d%d%d%d",parityTest,i,ii,idx,BitStream[idx+ii+(i*5)-5],BitStream[idx+ii+(i*5)-4],BitStream[idx+ii+(i*5)-3],BitStream[idx+ii+(i*5)-2],BitStream[idx+ii+(i*5)-1]);
  65                     parityTest=0;
  66                     idx-=8;
  67                     if (resetCnt>5)return 0;
  68                     resetCnt++;
  69                     goto restart;//continue;
  70                 }
  71             }
  72             //skip last 5 bit parity test for simplicity.
  73             return lo;
  74         }else{
  75             idx++;
  76         }
  77     }
  78     return 0;
  79 }
  80
  81 //by marshmellow
  82 //takes 2 arguments - clock and invert both as integers
  83 //attempts to demodulate ask while decoding manchester
  84 //prints binary found and saves in graphbuffer for further commands
  85 int askmandemod(uint8_t * BinStream,uint32_t *BitLen,int *clk, int *invert)
  86 {
  87     int i;
  88     int high = 0, low = 128;
  89     *clk=DetectASKClock(BinStream,(size_t)*BitLen,*clk); //clock default
  90
  91     if (*clk<8) *clk =64;
  92     if (*clk<32) *clk=32;
  93     if (*invert != 0 && *invert != 1) *invert=0;
  94     uint32_t initLoopMax = 200;
  95     if (initLoopMax>*BitLen) initLoopMax=*BitLen;
  96     // Detect high and lows
  97     for (i = 0; i < initLoopMax; ++i) //200 samples should be enough to find high and low values
  98     {
  99         if (BinStream[i] > high)
 100             high = BinStream[i];
 101         else if (BinStream[i] < low)
 102             low = BinStream[i];
 103     }
 104     if ((high < 158) ){  //throw away static
 105         //PrintAndLog("no data found");
 106         return -2;
 107     }
 108     //25% fuzz in case highs and lows aren't clipped [marshmellow]
 109     high=(int)((high-128)*.75)+128;
 110     low= (int)((low-128)*.75)+128;
 111
 112     //PrintAndLog("DEBUG - valid high: %d - valid low: %d",high,low);
 113     int lastBit = 0;  //set first clock check
 114     uint32_t bitnum = 0;     //output counter
 115     int tol = 0;  //clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
 116     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
 117     int iii = 0;
 118     uint32_t gLen = *BitLen;
 119     if (gLen > 3000) gLen=3000;
 120     uint8_t errCnt =0;
 121     uint32_t bestStart = *BitLen;
 122     uint32_t bestErrCnt = (*BitLen/1000);
 123     uint32_t maxErr = (*BitLen/1000);
 124     //PrintAndLog("DEBUG - lastbit - %d",lastBit);
 125     //loop to find first wave that works
 126     for (iii=0; iii < gLen; ++iii){
 127         if ((BinStream[iii]>=high)||(BinStream[iii]<=low)){
 128             lastBit=iii-*clk;
 129             errCnt=0;
 130             //loop through to see if this start location works
 131             for (i = iii; i < *BitLen; ++i) {
 132                 if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
 133                     lastBit+=*clk;
 134                 } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
 135                     //low found and we are expecting a bar
 136                     lastBit+=*clk;
 137                 } else {
 138                     //mid value found or no bar supposed to be here
 139                     if ((i-lastBit)>(*clk+tol)){
 140                         //should have hit a high or low based on clock!!
 141
 142                         //debug
 143                         //PrintAndLog("DEBUG - no wave in expected area - location: %d, expected: %d-%d, lastBit: %d - resetting search",i,(lastBit+(clk-((int)(tol)))),(lastBit+(clk+((int)(tol)))),lastBit);
 144
 145                         errCnt++;
 146                         lastBit+=*clk;//skip over until hit too many errors
 147                         if (errCnt>(maxErr)) break;  //allow 1 error for every 1000 samples else start over
 148                     }
 149                 }
 150                 if ((i-iii) >(400 * *clk)) break; //got plenty of bits
 151             }
 152             //we got more than 64 good bits and not all errors
 153             if ((((i-iii)/ *clk) > (64+errCnt)) && (errCnt<maxErr)) {
 154                 //possible good read
 155                 if (errCnt==0){
 156                     bestStart=iii;
 157                     bestErrCnt=errCnt;
 158                     break;  //great read - finish
 159                 }
 160                 if (errCnt<bestErrCnt){  //set this as new best run
 161                     bestErrCnt=errCnt;
 162                     bestStart = iii;
 163                 }
 164             }
 165         }
 166     }
 167     if (bestErrCnt<maxErr){
 168         //best run is good enough set to best run and set overwrite BinStream
 169         iii=bestStart;
 170         lastBit=bestStart-*clk;
 171         bitnum=0;
 172         for (i = iii; i < *BitLen; ++i) {
 173             if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
 174                 lastBit+=*clk;
 175                 BinStream[bitnum] =  *invert;
 176                 bitnum++;
 177             } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
 178                 //low found and we are expecting a bar
 179                 lastBit+=*clk;
 180                 BinStream[bitnum] = 1-*invert;
 181                 bitnum++;
 182             } else {
 183                 //mid value found or no bar supposed to be here
 184                 if ((i-lastBit)>(*clk+tol)){
 185                     //should have hit a high or low based on clock!!
 186
 187                     //debug
 188                     //PrintAndLog("DEBUG - no wave in expected area - location: %d, expected: %d-%d, lastBit: %d - resetting search",i,(lastBit+(clk-((int)(tol)))),(lastBit+(clk+((int)(tol)))),lastBit);
 189                     if (bitnum > 0){
 190                         BinStream[bitnum]=77;
 191                         bitnum++;
 192                     }
 193
 194                     lastBit+=*clk;//skip over error
 195                 }
 196             }
 197             if (bitnum >=400) break;
 198         }
 199         *BitLen=bitnum;
 200     } else{
 201         *invert=bestStart;
 202         *clk=iii;
 203         return -1;
 204     }
 205     return bestErrCnt;
 206 }
 207
 208 //by marshmellow
 209 //take 10 and 01 and manchester decode
 210 //run through 2 times and take least errCnt
 211 int manrawdecode(uint8_t * BitStream, int *bitLen)
 212 {
 213     int bitnum=0;
 214     int errCnt =0;
 215     int i=1;
 216     int bestErr = 1000;
 217     int bestRun = 0;
 218     int ii=1;
 219     for (ii=1;ii<3;++ii){
 220         i=1;
 221         for (i=i+ii;i<*bitLen-2;i+=2){
 222             if(BitStream[i]==1 && (BitStream[i+1]==0)){
 223             } else if((BitStream[i]==0)&& BitStream[i+1]==1){
 224             } else {
 225                 errCnt++;
 226             }
 227             if(bitnum>300) break;
 228         }
 229         if (bestErr>errCnt){
 230             bestErr=errCnt;
 231             bestRun=ii;
 232         }
 233         errCnt=0;
 234     }
 235     errCnt=bestErr;
 236     if (errCnt<20){
 237         ii=bestRun;
 238         i=1;
 239         for (i=i+ii;i<*bitLen-2;i+=2){
 240             if(BitStream[i]==1 && (BitStream[i+1]==0)){
 241                 BitStream[bitnum++]=0;
 242             } else if((BitStream[i]==0)&& BitStream[i+1]==1){
 243                 BitStream[bitnum++]=1;
 244             } else {
 245                 BitStream[bitnum++]=77;
 246                 //errCnt++;
 247             }
 248             if(bitnum>300) break;
 249         }
 250         *bitLen=bitnum;
 251     }
 252     return errCnt;
 253 }
 254
 255
 256 //by marshmellow
 257 //take 01 or 10 = 0 and 11 or 00 = 1
 258 int BiphaseRawDecode(uint8_t * BitStream, int *bitLen, int offset)
 259 {
 260     uint8_t bitnum=0;
 261     uint32_t errCnt =0;
 262     uint32_t i=1;
 263     i=offset;
 264     for (;i<*bitLen-2;i+=2){
 265         if((BitStream[i]==1 && BitStream[i+1]==0)||(BitStream[i]==0 && BitStream[i+1]==1)){
 266             BitStream[bitnum++]=1;
 267         } else if((BitStream[i]==0 && BitStream[i+1]==0)||(BitStream[i]==1 && BitStream[i+1]==1)){
 268             BitStream[bitnum++]=0;
 269         } else {
 270             BitStream[bitnum++]=77;
 271             errCnt++;
 272         }
 273         if(bitnum>250) break;
 274     }
 275     *bitLen=bitnum;
 276     return errCnt;
 277 }
 278
 279 //by marshmellow
 280 //takes 2 arguments - clock and invert both as integers
 281 //attempts to demodulate ask only
 282 //prints binary found and saves in graphbuffer for further commands
 283 int askrawdemod(uint8_t *BinStream, int *bitLen,int *clk, int *invert)
 284 {
 285     uint32_t i;
 286     // int invert=0;  //invert default
 287     int high = 0, low = 128;
 288     *clk=DetectASKClock(BinStream,*bitLen,*clk); //clock default
 289     uint8_t BitStream[502] = {0};
 290
 291     if (*clk<8) *clk =64;
 292     if (*clk<32) *clk=32;
 293     if (*invert != 0 && *invert != 1) *invert =0;
 294     uint32_t initLoopMax = 200;
 295     if (initLoopMax>*bitLen) initLoopMax=*bitLen;
 296     // Detect high and lows
 297     for (i = 0; i < initLoopMax; ++i) //200 samples should be plenty to find high and low values
 298     {
 299         if (BinStream[i] > high)
 300             high = BinStream[i];
 301         else if (BinStream[i] < low)
 302             low = BinStream[i];
 303     }
 304     if ((high < 158)){  //throw away static
 305         //   PrintAndLog("no data found");
 306         return -2;
 307     }
 308     //25% fuzz in case highs and lows aren't clipped [marshmellow]
 309     high=(int)((high-128)*.75)+128;
 310     low= (int)((low-128)*.75)+128;
 311
 312     //PrintAndLog("DEBUG - valid high: %d - valid low: %d",high,low);
 313     int lastBit = 0;  //set first clock check
 314     uint32_t bitnum = 0;     //output counter
 315     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
 316     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
 317     uint32_t iii = 0;
 318     uint32_t gLen = *bitLen;
 319     if (gLen > 500) gLen=500;
 320     uint8_t errCnt =0;
 321     uint32_t bestStart = *bitLen;
 322     uint32_t bestErrCnt = (*bitLen/1000);
 323     uint8_t midBit=0;
 324     //PrintAndLog("DEBUG - lastbit - %d",lastBit);
 325     //loop to find first wave that works
 326     for (iii=0; iii < gLen; ++iii){
 327         if ((BinStream[iii]>=high)||(BinStream[iii]<=low)){
 328             lastBit=iii-*clk;
 329             //loop through to see if this start location works
 330             for (i = iii; i < *bitLen; ++i) {
 331                 if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
 332                     lastBit+=*clk;
 333                     BitStream[bitnum] =  *invert;
 334                     bitnum++;
 335                     midBit=0;
 336                 } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
 337                     //low found and we are expecting a bar
 338                     lastBit+=*clk;
 339                     BitStream[bitnum] = 1-*invert;
 340                     bitnum++;
 341                     midBit=0;
 342                 } else if ((BinStream[i]<=low) && (midBit==0) && ((i-lastBit)>((*clk/2)-tol))){
 343                     //mid bar?
 344                     midBit=1;
 345                     BitStream[bitnum]= 1-*invert;
 346                     bitnum++;
 347                 } else if ((BinStream[i]>=high)&&(midBit==0) && ((i-lastBit)>((*clk/2)-tol))){
 348                     //mid bar?
 349                     midBit=1;
 350                     BitStream[bitnum]= *invert;
 351                     bitnum++;
 352                 } else if ((i-lastBit)>((*clk/2)+tol)&&(midBit==0)){
 353                     //no mid bar found
 354                     midBit=1;
 355                     BitStream[bitnum]= BitStream[bitnum-1];
 356                     bitnum++;
 357                 } else {
 358                     //mid value found or no bar supposed to be here
 359
 360                     if ((i-lastBit)>(*clk+tol)){
 361                         //should have hit a high or low based on clock!!
 362                         //debug
 363                         //PrintAndLog("DEBUG - no wave in expected area - location: %d, expected: %d-%d, lastBit: %d - resetting search",i,(lastBit+(clk-((int)(tol)))),(lastBit+(clk+((int)(tol)))),lastBit);
 364                         if (bitnum > 0){
 365                             BitStream[bitnum]=77;
 366                             bitnum++;
 367                         }
 368
 369
 370                         errCnt++;
 371                         lastBit+=*clk;//skip over until hit too many errors
 372                         if (errCnt>((*bitLen/1000))){  //allow 1 error for every 1000 samples else start over
 373                             errCnt=0;
 374                             bitnum=0;//start over
 375                             break;
 376                         }
 377                     }
 378                 }
 379                 if (bitnum>500) break;
 380             }
 381             //we got more than 64 good bits and not all errors
 382             if ((bitnum > (64+errCnt)) && (errCnt<(*bitLen/1000))) {
 383                 //possible good read
 384                 if (errCnt==0) break;  //great read - finish
 385                 if (bestStart == iii) break;  //if current run == bestErrCnt run (after exhausted testing) then finish
 386                 if (errCnt<bestErrCnt){  //set this as new best run
 387                     bestErrCnt=errCnt;
 388                     bestStart = iii;
 389                 }
 390             }
 391         }
 392         if (iii>=gLen){ //exhausted test
 393             //if there was a ok test go back to that one and re-run the best run (then dump after that run)
 394             if (bestErrCnt < (*bitLen/1000)) iii=bestStart;
 395         }
 396     }
 397     if (bitnum>16){
 398
 399         // PrintAndLog("Data start pos:%d, lastBit:%d, stop pos:%d, numBits:%d",iii,lastBit,i,bitnum);
 400         //move BitStream back to BinStream
 401         // ClearGraph(0);
 402         for (i=0; i < bitnum; ++i){
 403             BinStream[i]=BitStream[i];
 404         }
 405         *bitLen=bitnum;
 406         // RepaintGraphWindow();
 407         //output
 408         // if (errCnt>0){
 409         //   PrintAndLog("# Errors during Demoding (shown as 77 in bit stream): %d",errCnt);
 410         // }
 411         // PrintAndLog("ASK decoded bitstream:");
 412         // Now output the bitstream to the scrollback by line of 16 bits
 413         // printBitStream2(BitStream,bitnum);
 414         //int errCnt=0;
 415         //errCnt=manrawdemod(BitStream,bitnum);
 416
 417         //   Em410xDecode(Cmd);
 418     } else return -1;
 419     return errCnt;
 420 }
 421 //translate wave to 11111100000 (1 for each short wave 0 for each long wave)
 422 size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow)
 423 {
 424     uint32_t last_transition = 0;
 425     uint32_t idx = 1;
 426     uint32_t maxVal=0;
 427     if (fchigh==0) fchigh=10;
 428     if (fclow==0) fclow=8;
 429     // we do care about the actual theshold value as sometimes near the center of the
 430     // wave we may get static that changes direction of wave for one value
 431     // if our value is too low it might affect the read.  and if our tag or
 432     // antenna is weak a setting too high might not see anything. [marshmellow]
 433     if (size<100) return 0;
 434     for(idx=1; idx<100; idx++){
 435         if(maxVal<dest[idx]) maxVal = dest[idx];
 436     }
 437     // set close to the top of the wave threshold with 25% margin for error
 438     // less likely to get a false transition up there.
 439     // (but have to be careful not to go too high and miss some short waves)
 440     uint8_t threshold_value = (uint8_t)(((maxVal-128)*.75)+128);
 441     //  idx=1;
 442     //uint8_t threshold_value = 127;
 443
 444     // sync to first lo-hi transition, and threshold
 445
 446     // Need to threshold first sample
 447
 448     if(dest[0] < threshold_value) dest[0] = 0;
 449     else dest[0] = 1;
 450
 451     size_t numBits = 0;
 452     // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
 453     // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere
 454     // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
 455     for(idx = 1; idx < size; idx++) {
 456         // threshold current value
 457
 458         if (dest[idx] < threshold_value) dest[idx] = 0;
 459         else dest[idx] = 1;
 460
 461         // Check for 0->1 transition
 462         if (dest[idx-1] < dest[idx]) { // 0 -> 1 transition
 463             if ((idx-last_transition)<(fclow-2)){            //0-5 = garbage noise
 464                 //do nothing with extra garbage
 465             } else if ((idx-last_transition) < (fchigh-1)) { //6-8 = 8 waves
 466                 dest[numBits]=1;
 467             } else {                                                    //9+ = 10 waves
 468                 dest[numBits]=0;
 469             }
 470             last_transition = idx;
 471             numBits++;
 472         }
 473     }
 474     return numBits; //Actually, it returns the number of bytes, but each byte represents a bit: 1 or 0
 475 }
 476
 477 uint32_t myround2(float f)
 478 {
 479     if (f >= 2000) return 2000;//something bad happened
 480     return (uint32_t) (f + (float)0.5);
 481 }
 482
 483 //translate 11111100000 to 10
 484 size_t aggregate_bits(uint8_t *dest,size_t size,  uint8_t rfLen, uint8_t maxConsequtiveBits, uint8_t invert,uint8_t fchigh,uint8_t fclow )// uint8_t h2l_crossing_value,uint8_t l2h_crossing_value,
 485 {
 486     uint8_t lastval=dest[0];
 487     uint32_t idx=0;
 488     size_t numBits=0;
 489     uint32_t n=1;
 490
 491     for( idx=1; idx < size; idx++) {
 492
 493         if (dest[idx]==lastval) {
 494             n++;
 495             continue;
 496         }
 497         //if lastval was 1, we have a 1->0 crossing
 498         if ( dest[idx-1]==1 ) {
 499             n=myround2((float)(n+1)/((float)(rfLen)/(float)fclow));
 500             //n=(n+1) / h2l_crossing_value;
 501         } else {// 0->1 crossing
 502             n=myround2((float)(n+1)/((float)(rfLen-2)/(float)fchigh));  //-2 for fudge factor
 503             //n=(n+1) / l2h_crossing_value;
 504         }
 505         if (n == 0) n = 1;
 506
 507         if(n < maxConsequtiveBits) //Consecutive
 508         {
 509             if(invert==0){ //invert bits
 510                 memset(dest+numBits, dest[idx-1] , n);
 511             }else{
 512                 memset(dest+numBits, dest[idx-1]^1 , n);
 513             }
 514             numBits += n;
 515         }
 516         n=0;
 517         lastval=dest[idx];
 518     }//end for
 519     return numBits;
 520 }
 521 //by marshmellow  (from holiman's base)
 522 // full fsk demod from GraphBuffer wave to decoded 1s and 0s (no mandemod)
 523 int fskdemod(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow)
 524 {
 525     // FSK demodulator
 526     size = fsk_wave_demod(dest, size, fchigh, fclow);
 527     size = aggregate_bits(dest, size,rfLen,192,invert,fchigh,fclow);
 528     return size;
 529 }
 530 // loop to get raw HID waveform then FSK demodulate the TAG ID from it
 531 int HIDdemodFSK(uint8_t *dest, size_t size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
 532 {
 533
 534     size_t idx=0; //, found=0; //size=0,
 535     // FSK demodulator
 536     size = fskdemod(dest, size,50,0,10,8);
 537
 538     // final loop, go over previously decoded manchester data and decode into usable tag ID
 539     // 111000 bit pattern represent start of frame, 01 pattern represents a 1 and 10 represents a 0
 540     uint8_t frame_marker_mask[] = {1,1,1,0,0,0};
 541     int numshifts = 0;
 542     idx = 0;
 543     //one scan
 544     while( idx + sizeof(frame_marker_mask) < size) {
 545         // search for a start of frame marker
 546         if ( memcmp(dest+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
 547         { // frame marker found
 548             idx+=sizeof(frame_marker_mask);
 549             while(dest[idx] != dest[idx+1] && idx < size-2)
 550             {
 551                 // Keep going until next frame marker (or error)
 552                 // Shift in a bit. Start by shifting high registers
 553                 *hi2 = (*hi2<<1)|(*hi>>31);
 554                 *hi = (*hi<<1)|(*lo>>31);
 555                 //Then, shift in a 0 or one into low
 556                 if (dest[idx] && !dest[idx+1])  // 1 0
 557                     *lo=(*lo<<1)|0;
 558                 else // 0 1
 559                     *lo=(*lo<<1)|1;
 560                 numshifts++;
 561                 idx += 2;
 562             }
 563             // Hopefully, we read a tag and      hit upon the next frame marker
 564             if(idx + sizeof(frame_marker_mask) < size)
 565             {
 566                 if ( memcmp(dest+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
 567                 {
 568                     //good return
 569                     return idx;
 570                 }
 571             }
 572             // reset
 573             *hi2 = *hi = *lo = 0;
 574             numshifts = 0;
 575         }else   {
 576             idx++;
 577         }
 578     }
 579     return -1;
 580 }
 581
 582 uint32_t bytebits_to_byte(uint8_t* src, int numbits)
 583 {
 584     uint32_t num = 0;
 585     for(int i = 0 ; i < numbits ; i++)
 586     {
 587         num = (num << 1) | (*src);
 588         src++;
 589     }
 590     return num;
 591 }
 592
 593 int IOdemodFSK(uint8_t *dest, size_t size)
 594 {
 595         static const uint8_t THRESHOLD = 140;
 596     uint32_t idx=0;
 597     //make sure buffer has data
 598     if (size < 66) return -1;
 599     //test samples are not just noise
 600         uint8_t justNoise = 1;
 601         for(idx=0;idx< size && justNoise ;idx++){
 602                 justNoise = dest[idx] < THRESHOLD;
 603         }
 604         if(justNoise) return 0;
 605
 606         // FSK demodulator
 607         size = fskdemod(dest, size,64,1,10,8);  //  RF/64 and invert
 608         if (size < 65) return -1;  //did we get a good demod?
 609         //Index map
 610         //0           10          20          30          40          50          60
 611         //|           |           |           |           |           |           |
 612         //01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
 613         //-----------------------------------------------------------------------------
 614         //00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
 615         //
 616         //XSF(version)facility:codeone+codetwo
 617         //Handle the data
 618         uint8_t mask[] = {0,0,0,0,0,0,0,0,0,1};
 619         for( idx=0; idx < (size - 65); idx++) {
 620                 if ( memcmp(dest + idx, mask, sizeof(mask))==0) {
 621                         //frame marker found
 622                         if (!dest[idx+8] && dest[idx+17]==1 && dest[idx+26]==1 && dest[idx+35]==1 && dest[idx+44]==1 && dest[idx+53]==1){
 623                                 //confirmed proper separator bits found
 624                                 //return start position
 625                                 return (int) idx;
 626                         }
 627                 }
 628         }
 629     return 0;
 630 }
 631
 632 // by marshmellow
 633 // not perfect especially with lower clocks or VERY good antennas (heavy wave clipping)
 634 // maybe somehow adjust peak trimming value based on samples to fix?
 635 int DetectASKClock(uint8_t dest[], size_t size, int clock)
 636 {
 637     int i=0;
 638     int peak=0;
 639     int low=128;
 640     int clk[]={16,32,40,50,64,100,128,256};
 641     int loopCnt = 256;  //don't need to loop through entire array...
 642     if (size<loopCnt) loopCnt = size;
 643
 644     //if we already have a valid clock quit
 645     for (;i<8;++i)
 646         if (clk[i]==clock) return clock;
 647
 648     //get high and low peak
 649     for (i=0;i<loopCnt;++i){
 650         if(dest[i]>peak){
 651             peak = dest[i];
 652         }
 653         if(dest[i]<low){
 654             low = dest[i];
 655         }
 656     }
 657     peak=(int)((peak-128)*.75)+128;
 658     low= (int)((low-128)*.75)+128;
 659     int ii;
 660     int clkCnt;
 661     int tol = 0;
 662     int bestErr=1000;
 663     int errCnt[]={0,0,0,0,0,0,0,0};
 664     //test each valid clock from smallest to greatest to see which lines up
 665     for(clkCnt=0; clkCnt<6;++clkCnt){
 666         if (clk[clkCnt]==32){
 667             tol=1;
 668         }else{
 669             tol=0;
 670         }
 671         bestErr=1000;
 672         //try lining up the peaks by moving starting point (try first 256)
 673         for (ii=0; ii<loopCnt; ++ii){
 674             if ((dest[ii]>=peak) || (dest[ii]<=low)){
 675                 errCnt[clkCnt]=0;
 676                 // now that we have the first one lined up test rest of wave array
 677                 for (i=0; i<((int)(size/clk[clkCnt])-1); ++i){
 678                     if (dest[ii+(i*clk[clkCnt])]>=peak || dest[ii+(i*clk[clkCnt])]<=low){
 679                     }else if(dest[ii+(i*clk[clkCnt])-tol]>=peak || dest[ii+(i*clk[clkCnt])-tol]<=low){
 680                     }else if(dest[ii+(i*clk[clkCnt])+tol]>=peak || dest[ii+(i*clk[clkCnt])+tol]<=low){
 681                     }else{  //error no peak detected
 682                         errCnt[clkCnt]++;
 683                     }
 684                 }
 685                 //if we found no errors this is correct one - return this clock
 686                 if(errCnt[clkCnt]==0) return clk[clkCnt];
 687                 //if we found errors see if it is lowest so far and save it as best run
 688                 if(errCnt[clkCnt]<bestErr) bestErr=errCnt[clkCnt];
 689             }
 690         }
 691     }
 692     int iii=0;
 693     int best=0;
 694     for (iii=0; iii<6;++iii){
 695         if (errCnt[iii]<errCnt[best]){
 696             best = iii;
 697         }
 698     }
 699     return clk[best];
 700 }