+/* Provides a framework for bidirectional LF tag communication\r
+ * Encoding is currently Hitag2, but the general idea can probably\r
+ * be transferred to other encodings.\r
+ * \r
+ * The new FPGA code will, for the LF simulator mode, give on SSC_FRAME\r
+ * (PA15) a thresholded version of the signal from the ADC. Setting the\r
+ * ADC path to the low frequency peak detection signal, will enable a\r
+ * somewhat reasonable receiver for modulation on the carrier signal\r
+ * that is generated by the reader. The signal is low when the reader\r
+ * field is switched off, and high when the reader field is active. Due\r
+ * to the way that the signal looks like, mostly only the rising edge is\r
+ * useful, your mileage may vary.\r
+ * \r
+ * Neat perk: PA15 can not only be used as a bit-banging GPIO, but is also\r
+ * TIOA1, which can be used as the capture input for timer 1. This should\r
+ * make it possible to measure the exact edge-to-edge time, without processor\r
+ * intervention.\r
+ * \r
+ * Arguments: divisor is the divisor to be sent to the FPGA (e.g. 95 for 125kHz)\r
+ * t0 is the carrier frequency cycle duration in terms of MCK (384 for 125kHz)\r
+ * \r
+ * The following defines are in carrier periods: \r
+ */\r
+#define HITAG_T_0_MIN 15 /* T[0] should be 18..22 */ \r
+#define HITAG_T_1_MIN 24 /* T[1] should be 26..30 */\r
+#define HITAG_T_EOF 40 /* T_EOF should be > 36 */\r
+#define HITAG_T_WRESP 208 /* T_wresp should be 204..212 */\r
+\r
+static void hitag_handle_frame(int t0, int frame_len, char *frame);\r
+//#define DEBUG_RA_VALUES 1\r
+#define DEBUG_FRAME_CONTENTS 1\r
+void SimulateTagLowFrequencyBidir(int divisor, int t0)\r
+{\r
+#if DEBUG_RA_VALUES || DEBUG_FRAME_CONTENTS\r
+ int i = 0;\r
+#endif\r
+ char frame[10];\r
+ int frame_pos=0;\r
+ \r
+ DbpString("Starting Hitag2 emulator, press button to end");\r
+ hitag2_init();\r
+ \r
+ /* Set up simulator mode, frequency divisor which will drive the FPGA\r
+ * and analog mux selection.
+ */\r
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);\r
+ FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);\r
+ SetAdcMuxFor(GPIO_MUXSEL_LOPKD);\r
+ RELAY_OFF();\r
+ \r
+ /* Set up Timer 1:\r
+ * Capture mode, timer source MCK/2 (TIMER_CLOCK1), TIOA is external trigger,\r
+ * external trigger rising edge, load RA on rising edge of TIOA, load RB on rising\r
+ * edge of TIOA. Assign PA15 to TIOA1 (peripheral B)
+ */\r
+ \r
+ PMC_PERIPHERAL_CLK_ENABLE = (1 << PERIPH_TC1);\r
+ PIO_PERIPHERAL_B_SEL = (1 << GPIO_SSC_FRAME);\r
+ TC1_CCR = TC_CCR_CLKDIS;\r
+ TC1_CMR = TC_CMR_TCCLKS_TIMER_CLOCK1 | TC_CMR_ETRGEDG_RISING | TC_CMR_ABETRG |\r
+ TC_CMR_LDRA_RISING | TC_CMR_LDRB_RISING;\r
+ TC1_CCR = TC_CCR_CLKEN | TC_CCR_SWTRG;\r
+ \r
+ /* calculate the new value for the carrier period in terms of TC1 values */\r
+ t0 = t0/2;\r
+ \r
+ int overflow = 0;\r
+ while(!BUTTON_PRESS()) {\r
+ WDT_HIT();\r
+ if(TC1_SR & TC_SR_LDRAS) {\r
+ int ra = TC1_RA;\r
+ if((ra > t0*HITAG_T_EOF) | overflow) ra = t0*HITAG_T_EOF+1;\r
+#if DEBUG_RA_VALUES\r
+ if(ra > 255 || overflow) ra = 255;\r
+ ((char*)BigBuf)[i] = ra;\r
+ i = (i+1) % 8000;\r
+#endif\r
+ \r
+ if(overflow || (ra > t0*HITAG_T_EOF) || (ra < t0*HITAG_T_0_MIN)) {\r
+ /* Ignore */\r
+ } else if(ra >= t0*HITAG_T_1_MIN ) {\r
+ /* '1' bit */\r
+ if(frame_pos < 8*sizeof(frame)) {\r
+ frame[frame_pos / 8] |= 1<<( 7-(frame_pos%8) );\r
+ frame_pos++;\r
+ }\r
+ } else if(ra >= t0*HITAG_T_0_MIN) {\r
+ /* '0' bit */\r
+ if(frame_pos < 8*sizeof(frame)) {\r
+ frame[frame_pos / 8] |= 0<<( 7-(frame_pos%8) );\r
+ frame_pos++;\r
+ }\r
+ }\r
+ \r
+ overflow = 0;\r
+ LED_D_ON();\r
+ } else {\r
+ if(TC1_CV > t0*HITAG_T_EOF) {\r
+ /* Minor nuisance: In Capture mode, the timer can not be\r
+ * stopped by a Compare C. There's no way to stop the clock\r
+ * in software, so we'll just have to note the fact that an\r
+ * overflow happened and the next loaded timer value might\r
+ * have wrapped. Also, this marks the end of frame, and the\r
+ * still running counter can be used to determine the correct\r
+ * time for the start of the reply.
+ */ \r
+ overflow = 1;\r
+ \r
+ if(frame_pos > 0) {\r
+ /* Have a frame, do something with it */\r
+#if DEBUG_FRAME_CONTENTS\r
+ ((char*)BigBuf)[i++] = frame_pos;\r
+ memcpy( ((char*)BigBuf)+i, frame, 7);\r
+ i+=7;\r
+ i = i % sizeof(BigBuf);\r
+#endif\r
+ hitag_handle_frame(t0, frame_pos, frame);\r
+ memset(frame, 0, sizeof(frame));\r
+ }\r
+ frame_pos = 0;\r
+\r
+ }\r
+ LED_D_OFF();\r
+ }\r
+ }\r
+ DbpString("All done");\r
+}\r
+\r
+static void hitag_send_bit(int t0, int bit) {\r
+ if(bit == 1) {\r
+ /* Manchester: Loaded, then unloaded */\r
+ LED_A_ON();\r
+ SHORT_COIL();\r
+ while(TC1_CV < t0*15);\r
+ OPEN_COIL();\r
+ while(TC1_CV < t0*31);\r
+ LED_A_OFF();\r
+ } else if(bit == 0) {\r
+ /* Manchester: Unloaded, then loaded */\r
+ LED_B_ON();\r
+ OPEN_COIL();\r
+ while(TC1_CV < t0*15);\r
+ SHORT_COIL();\r
+ while(TC1_CV < t0*31);\r
+ LED_B_OFF();\r
+ }\r
+ TC1_CCR = TC_CCR_SWTRG; /* Reset clock for the next bit */\r
+ \r
+}\r
+static void hitag_send_frame(int t0, int frame_len, const char const * frame, int fdt)\r
+{\r
+ OPEN_COIL();\r
+ PIO_OUTPUT_ENABLE = (1 << GPIO_SSC_DOUT);\r
+ \r
+ /* Wait for HITAG_T_WRESP carrier periods after the last reader bit,\r
+ * not that since the clock counts since the rising edge, but T_wresp is\r
+ * with respect to the falling edge, we need to wait actually (T_wresp - T_g)\r
+ * periods. The gap time T_g varies (4..10).
+ */\r
+ while(TC1_CV < t0*(fdt-8));\r
+\r
+ int saved_cmr = TC1_CMR;\r
+ TC1_CMR &= ~TC_CMR_ETRGEDG; /* Disable external trigger for the clock */\r
+ TC1_CCR = TC_CCR_SWTRG; /* Reset the clock and use it for response timing */\r
+ \r
+ int i;\r
+ for(i=0; i<5; i++)\r
+ hitag_send_bit(t0, 1); /* Start of frame */\r
+ \r
+ for(i=0; i<frame_len; i++) {\r
+ hitag_send_bit(t0, !!(frame[i/ 8] & (1<<( 7-(i%8) ))) );\r
+ }\r
+ \r
+ OPEN_COIL();\r
+ TC1_CMR = saved_cmr;\r
+}\r
+\r
+/* Callback structure to cleanly separate tag emulation code from the radio layer. */\r
+static int hitag_cb(const char* response_data, const int response_length, const int fdt, void *cb_cookie)\r
+{\r
+ hitag_send_frame(*(int*)cb_cookie, response_length, response_data, fdt);\r
+ return 0;\r
+}\r
+/* Frame length in bits, frame contents in MSBit first format */\r
+static void hitag_handle_frame(int t0, int frame_len, char *frame)\r
+{\r
+ hitag2_handle_command(frame, frame_len, hitag_cb, &t0);\r
+}\r
+\r
projects / proxmark3-svn / commitdiff