+/* Read the transmitted data of an EM4x50 tag\r
+ * Format:\r
+ *\r
+ * XXXXXXXX [row parity bit (even)] <- 8 bits plus parity\r
+ * XXXXXXXX [row parity bit (even)] <- 8 bits plus parity\r
+ * XXXXXXXX [row parity bit (even)] <- 8 bits plus parity\r
+ * XXXXXXXX [row parity bit (even)] <- 8 bits plus parity\r
+ * CCCCCCCC <- column parity bits\r
+ * 0 <- stop bit\r
+ * LW <- Listen Window\r
+ *\r
+ * This pattern repeats for every block of data being transmitted.\r
+ * Transmission starts with two Listen Windows (LW - a modulated\r
+ * pattern of 320 cycles each (32/32/128/64/64)).\r
+ *\r
+ * Note that this data may or may not be the UID. It is whatever data\r
+ * is stored in the blocks defined in the control word First and Last \r
+ * Word Read values. UID is stored in block 32.\r
+ */ \r
+static void CmdEM4x50read(char *str)\r
+{\r
+ int i, j, startblock, clock, skip, block, start, end, low, high;\r
+ BOOL complete= FALSE;\r
+ int tmpbuff[MAX_GRAPH_TRACE_LEN / 64];\r
+ char tmp[6];\r
+\r
+ high= low= 0;\r
+ clock= 64;\r
+\r
+ /* first get high and low values */\r
+ for (i = 0; i < GraphTraceLen; i++)\r
+ {\r
+ if (GraphBuffer[i] > high) \r
+ high = GraphBuffer[i];\r
+ else if (GraphBuffer[i] < low)\r
+ low = GraphBuffer[i];\r
+ }\r
+\r
+ /* populate a buffer with pulse lengths */\r
+ i= 0;\r
+ j= 0;\r
+ while(i < GraphTraceLen)\r
+ {\r
+ // measure from low to low\r
+ while(GraphBuffer[i] > low)\r
+ ++i;\r
+ start= i;\r
+ while(GraphBuffer[i] < high)\r
+ ++i;\r
+ while(GraphBuffer[i] > low)\r
+ ++i;\r
+ tmpbuff[j++]= i - start;\r
+ }\r
+\r
+ \r
+ /* look for data start - should be 2 pairs of LW (pulses of 192,128) */\r
+ start= -1;\r
+ skip= 0;\r
+ for (i= 0; i < j - 4 ; ++i)\r
+ {\r
+ skip += tmpbuff[i];\r
+ if (tmpbuff[i] >= 190 && tmpbuff[i] <= 194)\r
+ if (tmpbuff[i+1] >= 126 && tmpbuff[i+1] <= 130)\r
+ if (tmpbuff[i+2] >= 190 && tmpbuff[i+2] <= 194)\r
+ if (tmpbuff[i+3] >= 126 && tmpbuff[i+3] <= 130)\r
+ {\r
+ start= i + 3;\r
+ break;\r
+ }\r
+ }\r
+ startblock= i + 3;\r
+\r
+ /* skip over the remainder of the LW */\r
+ skip += tmpbuff[i+1]+tmpbuff[i+2];\r
+ while(GraphBuffer[skip] > low)\r
+ ++skip;\r
+ skip += 8;\r
+\r
+ /* now do it again to find the end */\r
+ end= start;\r
+ for (i += 3; i < j - 4 ; ++i)\r
+ {\r
+ end += tmpbuff[i];\r
+ if (tmpbuff[i] >= 190 && tmpbuff[i] <= 194)\r
+ if (tmpbuff[i+1] >= 126 && tmpbuff[i+1] <= 130)\r
+ if (tmpbuff[i+2] >= 190 && tmpbuff[i+2] <= 194)\r
+ if (tmpbuff[i+3] >= 126 && tmpbuff[i+3] <= 130)\r
+ {\r
+ complete= TRUE;\r
+ break;\r
+ }\r
+ }\r
+\r
+ if (start >= 0)\r
+ PrintToScrollback("Found data at sample: %i",skip);\r
+ else\r
+ {\r
+ PrintToScrollback("No data found!");\r
+ PrintToScrollback("Try again with more samples.");\r
+ return;\r
+ }\r
+\r
+ if (!complete)\r
+ {\r
+ PrintToScrollback("*** Warning!");\r
+ PrintToScrollback("Partial data - no end found!");\r
+ PrintToScrollback("Try again with more samples.");\r
+ }\r
+\r
+ /* get rid of leading crap */\r
+ sprintf(tmp,"%i",skip);\r
+ CmdLtrim(tmp);\r
+\r
+ /* now work through remaining buffer printing out data blocks */\r
+ block= 0;\r
+ i= startblock;\r
+ while(block < 6)\r
+ {\r
+ PrintToScrollback("Block %i:", block);\r
+ // mandemod routine needs to be split so we can call it for data\r
+ // just print for now for debugging\r
+ Cmdmanchesterdemod("i 64");\r
+ skip= 0;\r
+ /* look for LW before start of next block */\r
+ for ( ; i < j - 4 ; ++i)\r
+ {\r
+ skip += tmpbuff[i];\r
+ if (tmpbuff[i] >= 190 && tmpbuff[i] <= 194)\r
+ if (tmpbuff[i+1] >= 126 && tmpbuff[i+1] <= 130)\r
+ break;\r
+ }\r
+ while(GraphBuffer[skip] > low)\r
+ ++skip;\r
+ skip += 8;\r
+ sprintf(tmp,"%i",skip);\r
+ CmdLtrim(tmp);\r
+ start += skip;\r
+ block++;\r
+ }\r
+}\r
+\r
+\r
projects / proxmark3-svn / blobdiff