Add CCITT Kermit CRC check for FDX-B demod

diff --git a/client/cmddata.c b/client/cmddata.c
index dad0a71195311433f32686abc954cd1d1bb1b9e3..00caefd98c18b831ad991f9ed84b45dea86fe6cf 100644 (file)
--- a/client/cmddata.c
+++ b/client/cmddata.c
@@ -23,6 +23,7 @@
 #include "lfdemod.h"
 #include "usb_cmd.h"
 #include "crc.h"
+#include "crc16.h"
 
 uint8_t DemodBuffer[MAX_DEMOD_BUF_LEN];
 uint8_t g_debugMode;
@@ -1501,9 +1502,10 @@ int CmdFDXBdemodBI(const char *Cmd){
        if (g_debugMode) {
                char *bin = sprint_bin_break(BitStream,size,16);
                PrintAndLog("DEBUG BinStream:\n%s",bin);
+               PrintAndLog("0x%s", sprint_hex(BitStream,16));
        }
        PrintAndLog("\nFDX-B / ISO 11784/5 Animal Tag ID Found:");
-       if (g_debugMode) PrintAndLog("startmarker %d;   Size %d", preambleIndex, size);
+       if (g_debugMode) PrintAndLog("Start marker %d;   Size %d", preambleIndex, size);
 
        //return 1;
        //got a good demod
@@ -1515,14 +1517,22 @@ int CmdFDXBdemodBI(const char *Cmd){
        uint32_t crc16 = bytebits_to_byteLSBF(BitStream+64,16);
        uint32_t extended = bytebits_to_byteLSBF(BitStream+80,24);
 
+       uint64_t rawid = ((uint64_t)bytebits_to_byteLSBF(BitStream,32)<<32) | bytebits_to_byteLSBF(BitStream+32,32);
+       uint8_t raw[8];
+       num_to_bytes(rawid, 8, raw);
+       uint8_t *ID = SwapEndian64(raw, 8, 4);
+
+       if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(ID,8));
+
+       uint16_t calcCrc = crc16_ccitt_kermit(ID, 8);
        PrintAndLog("Animal ID:     %u-%012llu", countryCode, NationalCode);
        PrintAndLog("National Code: %012llu", NationalCode);
        PrintAndLog("CountryCode:   %u", countryCode);
        PrintAndLog("Extended Data: %s", dataBlockBit ? "True" : "False");
        PrintAndLog("reserved Code: %u", reservedCode);
        PrintAndLog("Animal Tag:    %s", animalBit ? "True" : "False");
-       PrintAndLog("CRC:           0x%02X", crc16);
-       PrintAndLog("Extended:      0x%X", extended);
+       PrintAndLog("CRC:           0x%04X - [%04X] - %s", crc16, calcCrc, (calcCrc == crc16) ? "Passed" : "Failed");
+       PrintAndLog("Extended:      0x%X\n", extended);
        
        return 1;
 }

diff --git a/common/crc16.c b/common/crc16.c
index 973cd103c009b16697b7523b1cbf60b107500f7a..d48df3b2c9f650720c1a4c39810010ce4f8ded44 100644 (file)
--- a/common/crc16.c
+++ b/common/crc16.c
@@ -11,35 +11,49 @@
 
 unsigned short update_crc16( unsigned short crc, unsigned char c )
 {
-  unsigned short i, v, tcrc = 0;
+       unsigned short 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;
-  }
+       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)&0xffff;
+       return ((crc >> 8) ^ tcrc)&0xffff;
 }
 
 uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial) {
-    
-       if (length == 0)
-        return (~remainder);
-                       
-    for (int byte = 0; byte < length; ++byte) {
-        remainder ^= (message[byte] << 8);
-        for (uint8_t bit = 8; bit > 0; --bit) {
-            if (remainder & 0x8000) {
-                remainder = (remainder << 1) ^ polynomial;
-            } else {
-                remainder = (remainder << 1);
-            }
-        }
-    }
-    return remainder;
+
+       if (length == 0) return (~remainder);
+
+       for (int byte = 0; byte < length; ++byte) {
+               remainder ^= (message[byte] << 8);
+               for (uint8_t bit = 8; bit > 0; --bit) {
+                       if (remainder & 0x8000) {
+                               remainder = (remainder << 1) ^ polynomial;
+                       } else {
+                               remainder = (remainder << 1);
+                       }
+               }
+       }
+       return remainder;
 }
 
 uint16_t crc16_ccitt(uint8_t const *message, int length) {
-    return crc16(message, length, 0xffff, 0x1021);
+       return crc16(message, length, 0xffff, 0x1021);
+}
+
+uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) {
+       if (length == 0) return 0;
+       uint32_t crc = 0, q = 0;
+       uint8_t c;
+
+       for (int i = 0; i < length; i++){
+               c = message[i];
+               q = (crc ^ c ) & 0xF;
+               crc = (crc >> 4) ^ (q * 0x1081);
+               q = (crc ^ (c >> 4)) & 0xF;
+               crc = (crc >> 4) ^ (q * 0x1081);
+       }
+       return crc;
 }

diff --git a/common/crc16.h b/common/crc16.h
index d16d83b5afdb162c088e35e4a01aee33e2760e3d..3656ce278c7b97ab4a8da3c6c0fdb20157196f93 100644 (file)
--- a/common/crc16.h
+++ b/common/crc16.h
@@ -12,4 +12,5 @@
 unsigned short update_crc16(unsigned short crc, unsigned char c);
 uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial);
 uint16_t crc16_ccitt(uint8_t const *message, int length);
+uint16_t crc16_ccitt_kermit(uint8_t const *message, int length);
 #endif