From 0c2ed92d876c32abce11daf86eea4bcece6fa6fa Mon Sep 17 00:00:00 2001 From: d18c7db 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<> 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<>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