From 0c2ed92d876c32abce11daf86eea4bcece6fa6fa Mon Sep 17 00:00:00 2001
From: d18c7db <d18c7db@ef4ab9da-24cd-11de-8aaa-f3a34680c41f>
Date: Wed, 22 Jul 2009 11:39:39 +0000
Subject: [PATCH] Further additions to tidemod to differentiate between ro and
rw tags and check crc validity.
---
armsrc/appmain.c | 2 +-
common/crc16.c | 11 +++++
winsrc/command.cpp | 108 ++++++++++++++++++++++++++++++++++++---------
3 files changed, 98 insertions(+), 23 deletions(-)
create mode 100644 common/crc16.c
diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index f42b0209..f35a82fa 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -256,7 +256,7 @@ void AcquireTiType(void)
WDT_HIT();
}
- // return stolen pin ro SSP
+ // return stolen pin to SSP
PIO_DISABLE = (1<<GPIO_SSC_DOUT);
PIO_PERIPHERAL_A_SEL = (1<<GPIO_SSC_DIN) | (1<<GPIO_SSC_DOUT);
}
diff --git a/common/crc16.c b/common/crc16.c
new file mode 100644
index 00000000..6cdf3ea3
--- /dev/null
+++ b/common/crc16.c
@@ -0,0 +1,11 @@
+unsigned short update_crc16( WORD crc, BYTE c ) {
+ WORD i, v, tcrc = 0;
+
+ v = (crc ^ c) & 0xff;
+ for (i = 0; i < 8; i++) {
+ tcrc = ( (tcrc ^ v) & 1 ) ? ( tcrc >> 1 ) ^ 0x8408 : tcrc >> 1;
+ v >>= 1;
+ }
+
+ return (crc >> 8) ^ tcrc;
+}
diff --git a/winsrc/command.cpp b/winsrc/command.cpp
index b186d217..4ac807d9 100644
--- a/winsrc/command.cpp
+++ b/winsrc/command.cpp
@@ -12,6 +12,7 @@
#include "prox.h"
#include "../common/iso14443_crc.c"
+#include "../common/crc16.c"
#define arraylen(x) (sizeof(x)/sizeof((x)[0]))
#define BIT(x) GraphBuffer[x * clock]
@@ -1608,8 +1609,8 @@ h = sign(sin(cumsum(h)));
};
int convLen = max(arraylen(HighTone), arraylen(LowTone));
-
- int i;
+ WORD crc;
+ int i, TagType;
for(i = 0; i < GraphTraceLen - convLen; i++) {
int j;
int lowSum = 0, highSum = 0;;
@@ -1644,17 +1645,29 @@ h = sign(sin(cumsum(h)));
RepaintGraphWindow();
- // Okay, so now we have unsliced soft decisions; find bit-sync, and then
- // get some bits.
+ // TI tag data format is 16 prebits, 8 start bits, 64 data bits,
+ // 16 crc CCITT bits, 8 stop bits, 15 end bits
+
+ // the 16 prebits are always low
+ // the 8 start and stop bits of a tag must match
+ // the start/stop prebits of a ro tag are 01111110
+ // the start/stop prebits of a rw tag are 11111110
+ // the 15 end bits of a ro tag are all low
+ // the 15 end bits of a rw tag match bits 15-1 of the data bits
+ // Okay, so now we have unsliced soft decisions;
+ // find bit-sync, and then get some bits.
+ // look for 17 low bits followed by 6 highs (common pattern for ro and rw tags)
int max = 0, maxPos = 0;
for(i = 0; i < 6000; i++) {
int j;
int dec = 0;
- for(j = 0; j < 8*arraylen(LowTone); j++) {
+ // searching 17 consecutive lows
+ for(j = 0; j < 17*arraylen(LowTone); j++) {
dec -= GraphBuffer[i+j];
}
- for(; j < 8*arraylen(LowTone) + 8*arraylen(HighTone); j++) {
+ // searching 7 consecutive highs
+ for(; j < 17*arraylen(LowTone) + 6*arraylen(HighTone); j++) {
dec += GraphBuffer[i+j];
}
if(dec > max) {
@@ -1662,14 +1675,18 @@ h = sign(sin(cumsum(h)));
maxPos = i;
}
}
- GraphBuffer[maxPos] = 800;
- GraphBuffer[maxPos+1] = -800;
- maxPos += 8*arraylen(LowTone);
+ // place a marker in the buffer to visually aid location
+ // of the start of sync
GraphBuffer[maxPos] = 800;
GraphBuffer[maxPos+1] = -800;
- maxPos += 8*arraylen(HighTone);
+ // advance pointer to start of actual data stream (after 16 pre and 8 start bits)
+ maxPos += 17*arraylen(LowTone);
+ maxPos += 6*arraylen(HighTone);
+
+ // place a marker in the buffer to visually aid location
+ // of the end of sync
GraphBuffer[maxPos] = 800;
GraphBuffer[maxPos+1] = -800;
@@ -1677,10 +1694,12 @@ h = sign(sin(cumsum(h)));
PrintToScrollback("length %d/%d", arraylen(HighTone), arraylen(LowTone));
- BYTE bits[64+16+8+1];
+ BYTE bits[1+64+16+8+16];
bits[sizeof(bits)-1] = '\0';
- for(i = 0; i < arraylen(bits); i++) {
+ DWORD shift3 = 0x7e000000, shift2 = 0, shift1 = 0, shift0 = 0;
+
+ for(i = 0; i < arraylen(bits)-1; i++) {
int high = 0;
int low = 0;
int j;
@@ -1690,30 +1709,75 @@ h = sign(sin(cumsum(h)));
for(j = 0; j < arraylen(HighTone); j++) {
high += GraphBuffer[maxPos+j];
}
+
if(high > low) {
bits[i] = '1';
maxPos += arraylen(HighTone);
+ // bitstream arrives lsb first so shift right
+ shift3 |= (1<<31);
} else {
bits[i] = '.';
maxPos += arraylen(LowTone);
}
+
+ // 128 bit right shift register
+ shift0 = (shift0>>1) | (shift1 << 31);
+ shift1 = (shift1>>1) | (shift2 << 31);
+ shift2 = (shift2>>1) | (shift3 << 31);
+ shift3 >>= 1;
+
+ // place a marker in the buffer between bits to visually aid location
GraphBuffer[maxPos] = 800;
GraphBuffer[maxPos+1] = -800;
}
- PrintToScrollback("bits: '%s'", bits);
+ PrintToScrollback("Info: raw tag bits = %s", bits);
- DWORD h = 0, l = 0;
- for(i = 0; i < 32; i++) {
- if(bits[i] == '1') {
- l |= (1<<i);
- }
+ TagType = (shift3>>8)&0xff;
+ if ( TagType != ((shift0>>16)&0xff) ) {
+ PrintToScrollback("Error: start and stop bits do not match!");
+ return;
+ }
+ else if (TagType == 0x7e) {
+ PrintToScrollback("Info: Readonly TI tag detected.");
+ return;
}
- for(i = 32; i < 64; i++) {
- if(bits[i] == '1') {
- h |= (1<<(i-32));
+ else if (TagType == 0xfe) {
+ PrintToScrollback("Info: Rewriteable TI tag detected.");
+
+ // put 64 bit data into shift1 and shift0
+ shift0 = (shift0>>24) | (shift1 << 8);
+ shift1 = (shift1>>24) | (shift2 << 8);
+
+ // align 16 bit crc into lower half of shift2
+ shift2 = ((shift2>>24) | (shift3 << 8)) & 0x0ffff;
+
+ // align 16 bit "end bits" or "ident" into lower half of shift3
+ shift3 >>= 16;
+
+ if ( (shift3^shift0)&0xffff ) {
+ PrintToScrollback("Error: Ident mismatch!");
+ }
+ // calculate CRC
+ crc=0;
+ crc = update_crc16(crc, (shift0)&0xff);
+ crc = update_crc16(crc, (shift0>>8)&0xff);
+ crc = update_crc16(crc, (shift0>>16)&0xff);
+ crc = update_crc16(crc, (shift0>>24)&0xff);
+ crc = update_crc16(crc, (shift1)&0xff);
+ crc = update_crc16(crc, (shift1>>8)&0xff);
+ crc = update_crc16(crc, (shift1>>16)&0xff);
+ crc = update_crc16(crc, (shift1>>24)&0xff);
+ PrintToScrollback("Info: Tag data = %08X%08X", shift1, shift0);
+ if (crc != (shift2&0xffff)) {
+ PrintToScrollback("Error: CRC mismatch, calculated %04X, got ^04X", crc, shift2&0xffff);
+ } else {
+ PrintToScrollback("Info: CRC %04X is good", crc);
}
}
- PrintToScrollback("hex: %08x %08x", h, l);
+ else {
+ PrintToScrollback("Unknown tag type.");
+ return;
+ }
}
static void CmdNorm(char *str)
--
2.39.5