-/*
- * Manchester demodulate a bitstream. The bitstream needs to be already in
- * the GraphBuffer as 0 and 1 values
- *
- * Give the clock rate as argument in order to help the sync - the algorithm
- * resyncs at each pulse anyway.
- *
- * Not optimized by any means, this is the 1st time I'm writing this type of
- * routine, feel free to improve...
- *
- * 1st argument: clock rate (as number of samples per clock rate)
- * Typical values can be 64, 32, 128...
- */
-int CmdManchesterDemod(const char *Cmd)
-{
- int i, j, invert= 0;
- int bit;
- int clock;
- int lastval = 0;
- int low = 0;
- int high = 0;
- int hithigh, hitlow, first;
- int lc = 0;
- int bitidx = 0;
- int bit2idx = 0;
- int warnings = 0;
-
- /* check if we're inverting output */
- if (*Cmd == 'i')
- {
- PrintAndLog("Inverting output");
- invert = 1;
- ++Cmd;
- do
- ++Cmd;
- while(*Cmd == ' '); // in case a 2nd argument was given
- }
-
- /* Holds the decoded bitstream: each clock period contains 2 bits */
- /* later simplified to 1 bit after manchester decoding. */
- /* Add 10 bits to allow for noisy / uncertain traces without aborting */
- /* int BitStream[GraphTraceLen*2/clock+10]; */
-
- /* But it does not work if compiling on WIndows: therefore we just allocate a */
- /* large array */
- uint8_t BitStream[MAX_GRAPH_TRACE_LEN] = {0};
-
- /* Detect high and lows */
- for (i = 0; i < GraphTraceLen; i++)
- {
- if (GraphBuffer[i] > high)
- high = GraphBuffer[i];
- else if (GraphBuffer[i] < low)
- low = GraphBuffer[i];
- }
-
- /* Get our clock */
- clock = GetAskClock(Cmd, high, 1);
-
- int tolerance = clock/4;
-
- /* Detect first transition */
- /* Lo-Hi (arbitrary) */
- /* skip to the first high */
- for (i= 0; i < GraphTraceLen; i++)
- if (GraphBuffer[i] == high)
- break;
- /* now look for the first low */
- for (; i < GraphTraceLen; i++)
- {
- if (GraphBuffer[i] == low)
- {
- lastval = i;
- break;
- }
- }
-
- /* If we're not working with 1/0s, demod based off clock */
- if (high != 1)
- {
- bit = 0; /* We assume the 1st bit is zero, it may not be
- * the case: this routine (I think) has an init problem.
- * Ed.
- */
- for (; i < (int)(GraphTraceLen / clock); i++)
- {
- hithigh = 0;
- hitlow = 0;
- first = 1;
-
- /* Find out if we hit both high and low peaks */
- for (j = 0; j < clock; j++)
- {
- if (GraphBuffer[(i * clock) + j] == high)
- hithigh = 1;
- else if (GraphBuffer[(i * clock) + j] == low)
- hitlow = 1;
-
- /* it doesn't count if it's the first part of our read
- because it's really just trailing from the last sequence */
- if (first && (hithigh || hitlow))
- hithigh = hitlow = 0;
- else
- first = 0;
-
- if (hithigh && hitlow)
- break;
- }
-
- /* If we didn't hit both high and low peaks, we had a bit transition */
- if (!hithigh || !hitlow)
- bit ^= 1;
-
- BitStream[bit2idx++] = bit ^ invert;
- }
- }
-
- /* standard 1/0 bitstream */
- else
- {
-
- /* Then detect duration between 2 successive transitions */
- for (bitidx = 1; i < GraphTraceLen; i++)
- {
- if (GraphBuffer[i-1] != GraphBuffer[i])
- {
- lc = i-lastval;
- lastval = i;
-
- // Error check: if bitidx becomes too large, we do not
- // have a Manchester encoded bitstream or the clock is really
- // wrong!
- if (bitidx > (GraphTraceLen*2/clock+8) ) {
- PrintAndLog("Error: the clock you gave is probably wrong, aborting.");
- return 0;
- }
- // Then switch depending on lc length:
- // Tolerance is 1/4 of clock rate (arbitrary)
- if (abs(lc-clock/2) < tolerance) {
- // Short pulse : either "1" or "0"
- BitStream[bitidx++]=GraphBuffer[i-1];
- } else if (abs(lc-clock) < tolerance) {
- // Long pulse: either "11" or "00"
- BitStream[bitidx++]=GraphBuffer[i-1];
- BitStream[bitidx++]=GraphBuffer[i-1];
- } else {
- // Error
- warnings++;
- PrintAndLog("Warning: Manchester decode error for pulse width detection.");
- PrintAndLog("(too many of those messages mean either the stream is not Manchester encoded, or clock is wrong)");
-
- if (warnings > 10)
- {
- PrintAndLog("Error: too many detection errors, aborting.");
- return 0;
- }
- }
- }
- }
-
- // At this stage, we now have a bitstream of "01" ("1") or "10" ("0"), parse it into final decoded bitstream
- // Actually, we overwrite BitStream with the new decoded bitstream, we just need to be careful
- // to stop output at the final bitidx2 value, not bitidx
- for (i = 0; i < bitidx; i += 2) {
- if ((BitStream[i] == 0) && (BitStream[i+1] == 1)) {
- BitStream[bit2idx++] = 1 ^ invert;
- } else if ((BitStream[i] == 1) && (BitStream[i+1] == 0)) {
- BitStream[bit2idx++] = 0 ^ invert;
- } else {
- // We cannot end up in this state, this means we are unsynchronized,
- // move up 1 bit:
- i++;
- warnings++;
- PrintAndLog("Unsynchronized, resync...");
- PrintAndLog("(too many of those messages mean the stream is not Manchester encoded)");
-
- if (warnings > 10)
- {
- PrintAndLog("Error: too many decode errors, aborting.");
- return 0;
- }
- }
- }
- }
-
- PrintAndLog("Manchester decoded bitstream");
- // Now output the bitstream to the scrollback by line of 16 bits
- for (i = 0; i < (bit2idx-16); i+=16) {
- PrintAndLog("%i %i %i %i %i %i %i %i %i %i %i %i %i %i %i %i",
- BitStream[i],
- BitStream[i+1],
- BitStream[i+2],
- BitStream[i+3],
- BitStream[i+4],
- BitStream[i+5],
- BitStream[i+6],
- BitStream[i+7],
- BitStream[i+8],
- BitStream[i+9],
- BitStream[i+10],
- BitStream[i+11],
- BitStream[i+12],
- BitStream[i+13],
- BitStream[i+14],
- BitStream[i+15]);
- }
- return 0;
-}
-
-/* Modulate our data into manchester */
-int CmdManchesterMod(const char *Cmd)
-{
- int i, j;
- int clock;
- int bit, lastbit, wave;
-
- /* Get our clock */
- clock = GetAskClock(Cmd, 0, 1);
-
- wave = 0;
- lastbit = 1;
- for (i = 0; i < (int)(GraphTraceLen / clock); i++)
- {
- bit = GraphBuffer[i * clock] ^ 1;
-
- for (j = 0; j < (int)(clock/2); j++)
- GraphBuffer[(i * clock) + j] = bit ^ lastbit ^ wave;
- for (j = (int)(clock/2); j < clock; j++)
- GraphBuffer[(i * clock) + j] = bit ^ lastbit ^ wave ^ 1;
-
- /* Keep track of how we start our wave and if we changed or not this time */
- wave ^= bit ^ lastbit;
- lastbit = bit;
- }
-
- RepaintGraphWindow();
- return 0;
-}
-
projects / proxmark3-svn / blobdiff