+
+//by marshmellow
+//countFC is to detect the field clock and bit clock rates.
+//for fsk or ask not psk or nrz
+uint32_t countFC(uint8_t *BitStream, size_t size)
+{
+ // get high/low thresholds
+ int high, low;
+ getHiLo(BitStream,10, &high, &low, 100, 100);
+ // get zero crossing
+ uint8_t zeroC = (high-low)/2+low;
+ uint8_t clk[]={8,16,32,40,50,64,100,128};
+ uint8_t fcLens[] = {0,0,0,0,0,0,0,0,0,0};
+ uint16_t fcCnts[] = {0,0,0,0,0,0,0,0,0,0};
+ uint8_t rfLens[] = {0,0,0,0,0,0,0,0,0,0,0};
+ // uint8_t rfCnts[] = {0,0,0,0,0,0,0,0,0,0};
+ uint8_t fcLensFnd = 0;
+ uint8_t rfLensFnd = 0;
+ uint8_t lastBit=0;
+ uint8_t curBit=0;
+ uint8_t lastFCcnt=0;
+ uint32_t errCnt=0;
+ uint32_t fcCounter = 0;
+ uint32_t rfCounter = 0;
+ uint8_t firstBitFnd = 0;
+ int i;
+
+ // prime i to first up transition
+ for (i = 1; i < size; i++)
+ if (BitStream[i]>=zeroC && BitStream[i-1]<zeroC)
+ break;
+
+ for (; i < size; i++){
+ curBit = BitStream[i];
+ lastBit = BitStream[i-1];
+ if (lastBit<zeroC && curBit >= zeroC){
+ // new up transition
+ fcCounter++;
+ rfCounter++;
+ if (fcCounter > 3 && fcCounter < 256){
+ //we've counted enough that it could be a valid field clock
+
+ //if we had 5 and now have 9 then go back to 8 (for when we get a fc 9 instead of an 8)
+ if (lastFCcnt==5 && fcCounter==9) fcCounter--;
+ //if odd and not rc/5 add one (for when we get a fc 9 instead of 10)
+ if ((fcCounter==9 && fcCounter & 1) || fcCounter==4) fcCounter++;
+
+ //look for bit clock (rf/xx)
+ if ((fcCounter<lastFCcnt || fcCounter>lastFCcnt)){
+ //not the same size as the last wave - start of new bit sequence
+
+ if (firstBitFnd>1){ //skip first wave change - probably not a complete bit
+ for (int ii=0; ii<10; ii++){
+ if (rfLens[ii]==rfCounter){
+ //rfCnts[ii]++;
+ rfCounter=0;
+ break;
+ }
+ }
+ if (rfCounter>0 && rfLensFnd<10){
+ //PrintAndLog("DEBUG: rfCntr %d, fcCntr %d",rfCounter,fcCounter);
+ //rfCnts[rfLensFnd]++;
+ rfLens[rfLensFnd++]=rfCounter;
+ }
+ } else {
+ //PrintAndLog("DEBUG i: %d",i);
+ firstBitFnd++;
+ }
+ rfCounter=0;
+ lastFCcnt=fcCounter;
+ }
+
+ // save last field clock count (fc/xx)
+ // find which fcLens to save it to:
+ for (int ii=0; ii<10; ii++){
+ if (fcLens[ii]==fcCounter){
+ fcCnts[ii]++;
+ fcCounter=0;
+ break;
+ }
+ }
+ if (fcCounter>0 && fcLensFnd<10){
+ //add new fc length
+ //PrintAndLog("FCCntr %d",fcCounter);
+ fcCnts[fcLensFnd]++;
+ fcLens[fcLensFnd++]=fcCounter;
+ }
+ } else{
+ // hmmm this should not happen often - count them
+ errCnt++;
+ }
+ // reset counter
+ fcCounter=0;
+ } else {
+ // count sample
+ fcCounter++;
+ rfCounter++;
+ }
+ }
+ // if too many errors return errors as negative number (IS THIS NEEDED?)
+ if (errCnt>100) return -1*errCnt;
+
+ uint8_t maxCnt1=0, best1=9, best2=9, best3=9, rfHighest=10, rfHighest2=10, rfHighest3=10;
+
+ // go through fclens and find which ones are bigest 2
+ for (i=0; i<10; i++){
+ // PrintAndLog("DEBUG: FC %d, Cnt %d, Errs %d, RF %d",fcLens[i],fcCnts[i],errCnt,rfLens[i]);
+
+ // get the 3 best FC values
+ if (fcCnts[i]>maxCnt1) {
+ best3=best2;
+ best2=best1;
+ maxCnt1=fcCnts[i];
+ best1=i;
+ } else if(fcCnts[i]>fcCnts[best2]){
+ best3=best2;
+ best2=i;
+ } else if(fcCnts[i]>fcCnts[best3]){
+ best3=i;
+ }
+ //get highest 2 RF values (might need to get more values to compare or compare all?)
+ if (rfLens[i]>rfLens[rfHighest]){
+ rfHighest3=rfHighest2;
+ rfHighest2=rfHighest;
+ rfHighest=i;
+ } else if(rfLens[i]>rfLens[rfHighest2]){
+ rfHighest3=rfHighest2;
+ rfHighest2=i;
+ } else if(rfLens[i]>rfLens[rfHighest3]){
+ rfHighest3=i;
+ }
+ }
+
+ // set allowed clock remainder tolerance to be 1 large field clock length
+ // we could have mistakenly made a 9 a 10 instead of an 8 or visa versa so rfLens could be 1 FC off
+ int tol1 = (fcLens[best1]>fcLens[best2]) ? fcLens[best1] : fcLens[best2];
+
+ // loop to find the highest clock that has a remainder less than the tolerance
+ // compare samples counted divided by
+ int ii=7;
+ for (; ii>=0; ii--){
+ if (rfLens[rfHighest] % clk[ii] < tol1 || rfLens[rfHighest] % clk[ii] > clk[ii]-tol1){
+ if (rfLens[rfHighest2] % clk[ii] < tol1 || rfLens[rfHighest2] % clk[ii] > clk[ii]-tol1){
+ if (rfLens[rfHighest3] % clk[ii] < tol1 || rfLens[rfHighest3] % clk[ii] > clk[ii]-tol1){
+ break;
+ }
+ }
+ }
+ }
+
+ if (ii<0) ii=7; // oops we went too far
+
+ // TODO: take top 3 answers and compare to known Field clocks to get top 2
+
+ uint32_t fcs=0;
+ // PrintAndLog("DEBUG: Best %d best2 %d best3 %d, clk %d, clk2 %d",fcLens[best1],fcLens[best2],fcLens[best3],clk[i],clk[ii]);
+ //
+
+ if (fcLens[best1]>fcLens[best2]){
+ fcs = (((uint32_t)clk[ii])<<16) | (((uint32_t)fcLens[best1])<<8) | ((fcLens[best2]));
+ } else {
+ fcs = (((uint32_t)clk[ii])<<16) | (((uint32_t)fcLens[best2])<<8) | ((fcLens[best1]));
+ }
+
+ return fcs;
+}
projects / proxmark3-svn / blobdiff