Merge pull request #166 from marshmellow42/master

[proxmark3-svn] / common / lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 5ed2d16ce835758fefa1b7adad9d104fe6577b45..7398f1b2d74b5ec586a3b3a11ff0f0e6b25cf344 100644 (file)
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -485,7 +485,7 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
 
        size_t numBits = 0;
        // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
-       // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere
+       // or 10 (fc/10) cycles but in practice due to noise etc we may end up with anywhere
        // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
        for(idx = 161; idx < size-20; idx++) {
                // threshold current value
@@ -1529,11 +1529,12 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
        uint8_t fndClk[] = {8,16,32,40,50,64,128};
        int clk = 0; 
        int tol = 0;
-       int i, j, skip, start, end, low, high, minClk;
+       int i, j, skip, start, end, low, high, minClk, waveStart;
        bool complete = false;
        int tmpbuff[bufsize / 64];
+       int waveLen[bufsize / 64];
        size_t testsize = (bufsize < 512) ? bufsize : 512;
-       //int phaseoff = 0;
+       int phaseoff = 0;
        high = low = 128;
        memset(tmpbuff, 0, sizeof(tmpbuff));
 
@@ -1541,7 +1542,6 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
                if (g_debugMode==2) prnt("DEBUG STT: just noise detected - quitting");
                return false; //just noise
        }
-
        i = 0;
        j = 0;
        minClk = 255;
@@ -1560,11 +1560,14 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
                start= i;
                while ((buffer[i] < high) && (i < bufsize))
                        ++i;
+               //first high point for this wave
+               waveStart = i;
                while ((buffer[i] > low) && (i < bufsize))
                        ++i;
                if (j >= (bufsize/64)) {
                        break;
                }
+               waveLen[j] = i - waveStart; //first high to first low
                tmpbuff[j++] = i - start;
                if (i-start < minClk && i < bufsize) {
                        minClk = i - start;
@@ -1592,10 +1595,10 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
        start = -1;
        for (i = 0; i < j - 4; ++i) {
                skip += tmpbuff[i];
-               if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol) {           //1 to 2 clocks depending on 2 bits prior
-                       if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol) {       //2 clocks
-                               if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol) { //1 1/2 to 2 clocks
-                                       if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= (clk*3)/2+tol) { //1 to 1 1/2 clocks for end of ST + first bit
+               if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) {           //1 to 2 clocks depending on 2 bits prior
+                       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
+                               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
+                                       if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
                                                start = i + 3;
                                                break;
                                        }
@@ -1608,7 +1611,11 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
                if (g_debugMode==2) prnt("DEBUG STT: first STT not found - quitting");
                return false;
        }
-
+       if (waveLen[i+2] > clk*1+tol)
+               phaseoff = 0;
+       else
+               phaseoff = clk/2;
+       
        // skip over the remainder of ST
        skip += clk*7/2; //3.5 clocks from tmpbuff[i] = end of st - also aligns for ending point
 
@@ -1617,9 +1624,9 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
        for (i += 3; i < j - 4; ++i) {
                end += tmpbuff[i];
                if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol) {           //1 to 2 clocks depending on 2 bits prior
-                       if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol) {       //2 clocks
-                               if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol) { //1 1/2 to 2 clocks
-                                       if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= (clk*3)/2+tol) { //1 to 1 1/2 clocks for end of ST + first bit
+                       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
+                               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
+                                       if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit
                                                complete = true;
                                                break;
                                        }
@@ -1627,12 +1634,13 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) {
                        }
                }
        }
+       end -= phaseoff;
        //didn't find second ST - ERROR
        if (!complete) {
                if (g_debugMode==2) prnt("DEBUG STT: second STT not found - quitting");
                return false;
        }
-       if (g_debugMode==2) prnt("DEBUG STT: start of data: %d end of data: %d, datalen: %d, clk: %d, bits: %d", skip, end, end-skip, clk, (end-skip)/clk);
+       if (g_debugMode==2) prnt("DEBUG STT: start of data: %d end of data: %d, datalen: %d, clk: %d, bits: %d, phaseoff: %d", skip, end, end-skip, clk, (end-skip)/clk, phaseoff);
        //now begin to trim out ST so we can use normal demod cmds
        start = skip;
        size_t datalen = end - start;