From 5a847b2629c49d72ea2fa5eb5d1697fdef8095c9 Mon Sep 17 00:00:00 2001
From: iceman1001 <iceman@iuse.se>
Date: Fri, 16 Apr 2021 21:35:14 +0200
Subject: [PATCH] lf pac demod - now also checks for inverted bitstream
---
client/src/cmdlfpac.c | 36 +++++++++++++++++++++++++++++-------
client/src/cmdlfpac.h | 2 +-
2 files changed, 30 insertions(+), 8 deletions(-)
diff --git a/client/src/cmdlfpac.c b/client/src/cmdlfpac.c
index 5c2ccd98c..f9d6b098c 100644
--- a/client/src/cmdlfpac.c
+++ b/client/src/cmdlfpac.c
@@ -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;
}
diff --git a/client/src/cmdlfpac.h b/client/src/cmdlfpac.h
index a2145051b..107280cdf 100644
--- a/client/src/cmdlfpac.h
+++ b/client/src/cmdlfpac.h
@@ -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