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lf pac demod - now also checks for inverted bitstream

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This commit is contained in:
iceman1001 2021-04-16 21:35:14 +02:00
parent d34ae56c11
commit 5a847b2629
2 changed files with 30 additions and 8 deletions
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36
client/src/cmdlfpac.c
View file

@ -123,8 +123,9 @@ int demodPac(bool verbose) {
PrintAndLogEx(DEBUG, "DEBUG: Error - PAC: NRZ Demod failed");
return PM3_ESOFT;
}
bool invert = false;
size_t size = DemodBufferLen;
int ans = detectPac(DemodBuffer, &size);
int ans = detectPac(DemodBuffer, &size, &invert);
if (ans < 0) {
if (ans == -1)
PrintAndLogEx(DEBUG, "DEBUG: Error - PAC: too few bits found");
@ -137,6 +138,12 @@ int demodPac(bool verbose) {
return PM3_ESOFT;
}
if (invert) {
for (size_t i = ans; i < ans + 128; i++) {
DemodBuffer[i] ^= 1;
}
}
setDemodBuff(DemodBuffer, 128, ans);
setClockGrid(g_DemodClock, g_DemodStartIdx + (ans * g_DemodClock));
@ -394,14 +401,29 @@ int CmdLFPac(const char *Cmd) {
}
// find PAC preamble in already demoded data
int detectPac(uint8_t *dest, size_t *size) {
if (*size < 128) return -1; //make sure buffer has data
int detectPac(uint8_t *dest, size_t *size, bool *invert) {
// make sure buffer has data
if (*size < 128)
return -1;
size_t startIdx = 0;
uint8_t preamble[] = {1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0};
if (!preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx))
return -2; //preamble not found
if (*size != 128) return -3; //wrong demoded size
//return start position
if (!preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx)) {
// preamble not found
uint8_t pre_inv[] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1};
if (!preambleSearch(dest, pre_inv, sizeof(pre_inv), size, &startIdx)) {
return -2;
} else {
*invert = true;
}
}
// wrong demoded size
if (*size != 128)
return -3;
// return start position
return (int)startIdx;
}

2
client/src/cmdlfpac.h
View file

@ -14,6 +14,6 @@
int CmdLFPac(const char *Cmd);
int demodPac(bool verbose);
int detectPac(uint8_t *dest, size_t *size);
int detectPac(uint8_t *dest, size_t *size, bool *invert);
#endif