* routine, feel free to improve...
*
* 1st argument: clock rate (as number of samples per clock rate)
+ * Typical values can be 64, 32, 128...
*/
static void Cmdmanchesterdemod(char *str) {
int i;
int lastval;
int lc = 0;
int bitidx = 0;
- int bitidx2;
+ int bit2idx = 0;
sscanf(str, "%i", &clock);
int tolerance = clock/4;
- /* Holds the decoded bitstream. */
- int BitStream[MAX_GRAPH_TRACE_LEN*2];
- int BitStream2[MAX_GRAPH_TRACE_LEN];
+ /* 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 */
+ int BitStream[MAX_GRAPH_TRACE_LEN];
/* Detect first transition */
- /* Lo-Hi (arbitrary) */
+ /* Lo-Hi (arbitrary) */
for(i=1;i<GraphTraceLen;i++) {
if (GraphBuffer[i-1]<GraphBuffer[i]) {
lastval = i;
}
/* Then detect duration between 2 successive transitions */
- /* At this stage, GraphTrace is either 0 or 1 */
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) ) {
+ PrintToScrollback("Error: the clock you gave is probably wrong, aborting.");
+ return;
+ }
// Then switch depending on lc length:
// Tolerance is 1/4 of clock rate (arbitrary)
- if ((lc-clock/2) < tolerance) {
- // Short pulse
+ if (abs(lc-clock/2) < tolerance) {
+ // Short pulse : either "1" or "0"
BitStream[bitidx++]=GraphBuffer[i-1];
- } else if ((lc-clock) < tolerance) {
- // Long pulse
+ } else if (abs(lc-clock) < tolerance) {
+ // Long pulse: either "11" or "00"
BitStream[bitidx++]=GraphBuffer[i-1];
BitStream[bitidx++]=GraphBuffer[i-1];
} else {
}
// At this stage, we now have a bitstream of "01" ("1") or "10" ("0"), parse it into final decoded bitstream
- for (bitidx2 = 0; bitidx2<bitidx; bitidx2 += 2) {
- if ((BitStream[bitidx2] == 0) && (BitStream[bitidx2+1] == 1)) {
- BitStream2[bitidx2/2] = 1;
- } else if ((BitStream[bitidx2] == 1) && (BitStream[bitidx2+1] == 0)) {
- BitStream2[bitidx2/2] = 0;
+ // 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;
+ } else if ((BitStream[i] == 1) && (BitStream[i+1] == 0)) {
+ BitStream[bit2idx++] = 0;
} else {
// We cannot end up in this state, this means we are unsynchronized,
// move up 1 bit:
- bitidx2++;
+ i++;
PrintToScrollback("Unsynchronized, resync...");
PrintToScrollback("(too many of those messages mean the stream is not Manchester encoded)");
}
}
PrintToScrollback("Manchester decoded bitstream \n---------");
// Now output the bitstream to the scrollback by line of 16 bits
- for (i = 0; i<bitidx/2; i+=16) {
+ for (i = 0; i < (bit2idx-16); i+=16) {
PrintToScrollback("%i %i %i %i %i %i %i %i %i %i %i %i %i %i %i %i",
- BitStream2[i],
- BitStream2[i+1],
- BitStream2[i+2],
- BitStream2[i+3],
- BitStream2[i+4],
- BitStream2[i+5],
- BitStream2[i+6],
- BitStream2[i+7],
- BitStream2[i+8],
- BitStream2[i+9],
- BitStream2[i+10],
- BitStream2[i+11],
- BitStream2[i+12],
- BitStream2[i+13],
- BitStream2[i+14],
- BitStream2[i+15]);
+ 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]);
}
}
static void CmdTest(char *str)\r
{\r
}\r
+
+/*
+ * Sets the divisor for LF frequency clock: lets the user choose any LF frequency below
+ * 600kHz.
+ */
+static void CmdSetDivisor(char *str)\r
+{\r
+ UsbCommand c;\r
+ c.cmd = CMD_SET_LF_DIVISOR;\r
+ c.ext1 = atoi(str);\r
+ if (( c.ext1<0) || (c.ext1>255)) {\r
+ PrintToScrollback("divisor must be between 19 and 255");\r
+ } else {\r
+ SendCommand(&c, FALSE);\r
+ PrintToScrollback("Divisor set, expected freq=%dHz", 12000000/(c.ext1+1));\r
+ }\r
+}\r
+\r
+static void CmdSweepLF(char *str)\r
+{\r
+ UsbCommand c;\r
+ c.cmd = CMD_SWEEP_LF;\r
+ SendCommand(&c, FALSE);\r
+}\r
+
+
\r
typedef void HandlerFunction(char *cmdline);\r
\r
"lcdreset", CmdLcdReset, "Hardware reset LCD",\r
"lcd", CmdLcd, "Send command/data to LCD",\r
"test", CmdTest, "Placeholder command for testing new code",\r
+ "setlfdivisor", CmdSetDivisor, "Drive LF antenna at 12Mhz/(divisor+1)",\r
+ "sweeplf", CmdSweepLF, "Sweep through LF freq range and store results in buffer",\r
"quit", CmdQuit, "quit program"\r
};\r
\r
projects / proxmark3-svn / blobdiff