]> git.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/lfops.c
small updates to hf mf restore1k
[proxmark3-svn] / armsrc / lfops.c
index a7e1f1df160f7adbce283ce510f55d98f6d1f106..21e068c16ab92e80901cbb3b13f3129c14636f30 100644 (file)
-//-----------------------------------------------------------------------------\r
-// Miscellaneous routines for low frequency tag operations.\r
-// Tags supported here so far are Texas Instruments (TI), HID\r
-// Also routines for raw mode reading/simulating of LF waveform\r
-//\r
-//-----------------------------------------------------------------------------\r
-#include <proxmark3.h>\r
-#include "apps.h"\r
-#include "hitag2.h"\r
-#include "crc16.h"\r
-\r
-void AcquireRawAdcSamples125k(BOOL at134khz)\r
-{\r
-       if (at134khz)\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-       else\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);\r
-\r
-       // Connect the A/D to the peak-detected low-frequency path.\r
-       SetAdcMuxFor(GPIO_MUXSEL_LOPKD);\r
-\r
-       // Give it a bit of time for the resonant antenna to settle.\r
-       SpinDelay(50);\r
-\r
-       // Now set up the SSC to get the ADC samples that are now streaming at us.\r
-       FpgaSetupSsc();\r
-\r
-       // Now call the acquisition routine\r
-       DoAcquisition125k();\r
-}\r
-\r
-// split into two routines so we can avoid timing issues after sending commands //\r
-void DoAcquisition125k(void)\r
-{\r
-       BYTE *dest = (BYTE *)BigBuf;\r
-       int n = sizeof(BigBuf);\r
-       int i;\r
-       \r
-       memset(dest, 0, n);\r
-       i = 0;\r
-       for(;;) {\r
-               if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {\r
-                       AT91C_BASE_SSC->SSC_THR = 0x43;\r
-                       LED_D_ON();\r
-               }\r
-               if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {\r
-                       dest[i] = (BYTE)AT91C_BASE_SSC->SSC_RHR;\r
-                       i++;\r
-                       LED_D_OFF();\r
-                       if (i >= n) break;\r
-               }\r
-       }\r
-       Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",\r
-                       dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);\r
-}\r
-\r
-void ModThenAcquireRawAdcSamples125k(int delay_off, int period_0, int period_1, BYTE *command)\r
-{\r
-       BOOL at134khz;\r
-\r
-       /* Make sure the tag is reset */\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);\r
-       SpinDelay(2500);\r
-       \r
-       // see if 'h' was specified\r
-       if (command[strlen((char *) command) - 1] == 'h')\r
-               at134khz = TRUE;\r
-       else\r
-               at134khz = FALSE;\r
-\r
-       if (at134khz)\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-       else\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);\r
-\r
-       // Give it a bit of time for the resonant antenna to settle.\r
-       SpinDelay(50);\r
-       // And a little more time for the tag to fully power up\r
-       SpinDelay(2000);\r
-\r
-       // Now set up the SSC to get the ADC samples that are now streaming at us.\r
-       FpgaSetupSsc();\r
-\r
-       // now modulate the reader field\r
-       while(*command != '\0' && *command != ' ') {\r
-               FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);\r
-               LED_D_OFF();\r
-               SpinDelayUs(delay_off);\r
-               if (at134khz)\r
-                       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-               else\r
-                       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz\r
-\r
-               FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);\r
-               LED_D_ON();\r
-               if(*(command++) == '0')\r
-                       SpinDelayUs(period_0);\r
-               else\r
-                       SpinDelayUs(period_1);\r
-       }\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);\r
-       LED_D_OFF();\r
-       SpinDelayUs(delay_off);\r
-       if (at134khz)\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-       else\r
-               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);\r
-\r
-       // now do the read\r
-       DoAcquisition125k();\r
-}\r
-\r
-/* blank r/w tag data stream\r
-...0000000000000000 01111111\r
-1010101010101010101010101010101010101010101010101010101010101010\r
-0011010010100001\r
-01111111\r
-101010101010101[0]000...\r
-\r
-[5555fe852c5555555555555555fe0000]\r
-*/\r
-void ReadTItag(void)\r
-{\r
-       // some hardcoded initial params\r
-       // when we read a TI tag we sample the zerocross line at 2Mhz\r
-       // TI tags modulate a 1 as 16 cycles of 123.2Khz\r
-       // TI tags modulate a 0 as 16 cycles of 134.2Khz\r
-       #define FSAMPLE 2000000\r
-       #define FREQLO 123200\r
-       #define FREQHI 134200\r
-\r
-       signed char *dest = (signed char *)BigBuf;\r
-       int n = sizeof(BigBuf);\r
-//     int *dest = GraphBuffer;\r
-//     int n = GraphTraceLen;\r
-\r
-       // 128 bit shift register [shift3:shift2:shift1:shift0]\r
-       DWORD shift3 = 0, shift2 = 0, shift1 = 0, shift0 = 0;\r
-\r
-       int i, cycles=0, samples=0;\r
-       // how many sample points fit in 16 cycles of each frequency\r
-       DWORD sampleslo = (FSAMPLE<<4)/FREQLO, sampleshi = (FSAMPLE<<4)/FREQHI;\r
-       // when to tell if we're close enough to one freq or another\r
-       DWORD threshold = (sampleslo - sampleshi + 1)>>1;\r
-\r
-       // TI tags charge at 134.2Khz\r
-       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-\r
-       // Place FPGA in passthrough mode, in this mode the CROSS_LO line\r
-       // connects to SSP_DIN and the SSP_DOUT logic level controls\r
-       // whether we're modulating the antenna (high)\r
-       // or listening to the antenna (low)\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);\r
-\r
-       // get TI tag data into the buffer\r
-       AcquireTiType();\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);\r
-\r
-       for (i=0; i<n-1; i++) {\r
-               // count cycles by looking for lo to hi zero crossings\r
-               if ( (dest[i]<0) && (dest[i+1]>0) ) {\r
-                       cycles++;\r
-                       // after 16 cycles, measure the frequency\r
-                       if (cycles>15) {\r
-                               cycles=0;\r
-                               samples=i-samples; // number of samples in these 16 cycles\r
-\r
-                               // TI bits are coming to us lsb first so shift them\r
-                               // right through our 128 bit right shift register\r
-                         shift0 = (shift0>>1) | (shift1 << 31);\r
-                         shift1 = (shift1>>1) | (shift2 << 31);\r
-                         shift2 = (shift2>>1) | (shift3 << 31);\r
-                         shift3 >>= 1;\r
-\r
-                               // check if the cycles fall close to the number\r
-                               // expected for either the low or high frequency\r
-                               if ( (samples>(sampleslo-threshold)) && (samples<(sampleslo+threshold)) ) {\r
-                                       // low frequency represents a 1\r
-                                       shift3 |= (1<<31);\r
-                               } else if ( (samples>(sampleshi-threshold)) && (samples<(sampleshi+threshold)) ) {\r
-                                       // high frequency represents a 0\r
-                               } else {\r
-                                       // probably detected a gay waveform or noise\r
-                                       // use this as gaydar or discard shift register and start again\r
-                                       shift3 = shift2 = shift1 = shift0 = 0;\r
-                               }\r
-                               samples = i;\r
-\r
-                               // for each bit we receive, test if we've detected a valid tag\r
-\r
-                               // if we see 17 zeroes followed by 6 ones, we might have a tag\r
-                               // remember the bits are backwards\r
-                               if ( ((shift0 & 0x7fffff) == 0x7e0000) ) {\r
-                                       // if start and end bytes match, we have a tag so break out of the loop\r
-                                       if ( ((shift0>>16)&0xff) == ((shift3>>8)&0xff) ) {\r
-                                               cycles = 0xF0B; //use this as a flag (ugly but whatever)\r
-                                               break;\r
-                                       }\r
-                               }\r
-                       }\r
-               }\r
-       }\r
-\r
-       // if flag is set we have a tag\r
-       if (cycles!=0xF0B) {\r
-               DbpString("Info: No valid tag detected.");\r
-       } else {\r
-         // put 64 bit data into shift1 and shift0\r
-         shift0 = (shift0>>24) | (shift1 << 8);\r
-         shift1 = (shift1>>24) | (shift2 << 8);\r
-\r
-               // align 16 bit crc into lower half of shift2\r
-         shift2 = ((shift2>>24) | (shift3 << 8)) & 0x0ffff;\r
-\r
-               // if r/w tag, check ident match\r
-               if ( shift3&(1<<15) ) {\r
-                       DbpString("Info: TI tag is rewriteable");\r
-                       // only 15 bits compare, last bit of ident is not valid\r
-                       if ( ((shift3>>16)^shift0)&0x7fff ) {\r
-                               DbpString("Error: Ident mismatch!");\r
-                       } else {\r
-                               DbpString("Info: TI tag ident is valid");\r
-                       }\r
-               } else {\r
-                       DbpString("Info: TI tag is readonly");\r
-               }\r
-\r
-               // WARNING the order of the bytes in which we calc crc below needs checking\r
-               // i'm 99% sure the crc algorithm is correct, but it may need to eat the\r
-               // bytes in reverse or something\r
-               // calculate CRC\r
-               DWORD crc=0;\r
-\r
-               crc = update_crc16(crc, (shift0)&0xff);\r
-               crc = update_crc16(crc, (shift0>>8)&0xff);\r
-               crc = update_crc16(crc, (shift0>>16)&0xff);\r
-               crc = update_crc16(crc, (shift0>>24)&0xff);\r
-               crc = update_crc16(crc, (shift1)&0xff);\r
-               crc = update_crc16(crc, (shift1>>8)&0xff);\r
-               crc = update_crc16(crc, (shift1>>16)&0xff);\r
-               crc = update_crc16(crc, (shift1>>24)&0xff);\r
-\r
-               Dbprintf("Info: Tag data: %x%08x, crc=%x",\r
-                       (unsigned int)shift1, (unsigned int)shift0, (unsigned int)shift2 & 0xFFFF);\r
-               if (crc != (shift2&0xffff)) {\r
-                       Dbprintf("Error: CRC mismatch, expected %x", (unsigned int)crc);\r
-               } else {\r
-                       DbpString("Info: CRC is good");\r
-               }\r
-       }\r
-}\r
-\r
-void WriteTIbyte(BYTE b)\r
-{\r
-       int i = 0;\r
-\r
-       // modulate 8 bits out to the antenna\r
-       for (i=0; i<8; i++)\r
-       {\r
-               if (b&(1<<i)) {\r
-                       // stop modulating antenna\r
-                       LOW(GPIO_SSC_DOUT);\r
-                       SpinDelayUs(1000);\r
-                       // modulate antenna\r
-                       HIGH(GPIO_SSC_DOUT);\r
-                       SpinDelayUs(1000);\r
-               } else {\r
-                       // stop modulating antenna\r
-                       LOW(GPIO_SSC_DOUT);\r
-                       SpinDelayUs(300);\r
-                       // modulate antenna\r
-                       HIGH(GPIO_SSC_DOUT);\r
-                       SpinDelayUs(1700);\r
-               }\r
-       }\r
-}\r
-\r
-void AcquireTiType(void)\r
-{\r
-       int i, j, n;\r
-       // tag transmission is <20ms, sampling at 2M gives us 40K samples max\r
-       // each sample is 1 bit stuffed into a DWORD so we need 1250 DWORDS\r
-       #define TIBUFLEN 1250\r
-\r
-       // clear buffer\r
-       memset(BigBuf,0,sizeof(BigBuf));\r
-\r
-       // Set up the synchronous serial port\r
-       AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DIN;\r
-       AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN;\r
-\r
-       // steal this pin from the SSP and use it to control the modulation\r
-       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;\r
-       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;\r
-\r
-       AT91C_BASE_SSC->SSC_CR = AT91C_SSC_SWRST;\r
-       AT91C_BASE_SSC->SSC_CR = AT91C_SSC_RXEN | AT91C_SSC_TXEN;\r
-\r
-       // Sample at 2 Mbit/s, so TI tags are 16.2 vs. 14.9 clocks long\r
-       // 48/2 = 24 MHz clock must be divided by 12\r
-       AT91C_BASE_SSC->SSC_CMR = 12;\r
-\r
-       AT91C_BASE_SSC->SSC_RCMR = SSC_CLOCK_MODE_SELECT(0);\r
-       AT91C_BASE_SSC->SSC_RFMR = SSC_FRAME_MODE_BITS_IN_WORD(32) | AT91C_SSC_MSBF;\r
-       AT91C_BASE_SSC->SSC_TCMR = 0;\r
-       AT91C_BASE_SSC->SSC_TFMR = 0;\r
-\r
-       LED_D_ON();\r
-\r
-       // modulate antenna\r
-       HIGH(GPIO_SSC_DOUT);\r
-\r
-       // Charge TI tag for 50ms.\r
-       SpinDelay(50);\r
-\r
-       // stop modulating antenna and listen\r
-       LOW(GPIO_SSC_DOUT);\r
-\r
-       LED_D_OFF();\r
-\r
-       i = 0;\r
-       for(;;) {\r
-               if(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {\r
-                       BigBuf[i] = AT91C_BASE_SSC->SSC_RHR;    // store 32 bit values in buffer\r
-                       i++; if(i >= TIBUFLEN) break;\r
-               }\r
-               WDT_HIT();\r
-       }\r
-\r
-       // return stolen pin to SSP\r
-       AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DOUT;\r
-       AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN | GPIO_SSC_DOUT;\r
-\r
-       char *dest = (char *)BigBuf;\r
-       n = TIBUFLEN*32;\r
-       // unpack buffer\r
-       for (i=TIBUFLEN-1; i>=0; i--) {\r
-               for (j=0; j<32; j++) {\r
-                       if(BigBuf[i] & (1 << j)) {\r
-                               dest[--n] = 1;\r
-                       } else {\r
-                               dest[--n] = -1;\r
-                       }\r
-               }\r
-       }\r
-}\r
-\r
-// arguments: 64bit data split into 32bit idhi:idlo and optional 16bit crc\r
-// if crc provided, it will be written with the data verbatim (even if bogus)\r
-// if not provided a valid crc will be computed from the data and written.\r
-void WriteTItag(DWORD idhi, DWORD idlo, WORD crc)\r
-{\r
-       if(crc == 0) {\r
-               crc = update_crc16(crc, (idlo)&0xff);\r
-               crc = update_crc16(crc, (idlo>>8)&0xff);\r
-               crc = update_crc16(crc, (idlo>>16)&0xff);\r
-               crc = update_crc16(crc, (idlo>>24)&0xff);\r
-               crc = update_crc16(crc, (idhi)&0xff);\r
-               crc = update_crc16(crc, (idhi>>8)&0xff);\r
-               crc = update_crc16(crc, (idhi>>16)&0xff);\r
-               crc = update_crc16(crc, (idhi>>24)&0xff);\r
-       }\r
-       Dbprintf("Writing to tag: %x%08x, crc=%x",\r
-               (unsigned int) idhi, (unsigned int) idlo, crc);\r
-\r
-       // TI tags charge at 134.2Khz\r
-       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz\r
-       // Place FPGA in passthrough mode, in this mode the CROSS_LO line\r
-       // connects to SSP_DIN and the SSP_DOUT logic level controls\r
-       // whether we're modulating the antenna (high)\r
-       // or listening to the antenna (low)\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);\r
-       LED_A_ON();\r
-\r
-       // steal this pin from the SSP and use it to control the modulation\r
-       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;\r
-       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;\r
-\r
-       // writing algorithm:\r
-       // a high bit consists of a field off for 1ms and field on for 1ms\r
-       // a low bit consists of a field off for 0.3ms and field on for 1.7ms\r
-       // initiate a charge time of 50ms (field on) then immediately start writing bits\r
-       // start by writing 0xBB (keyword) and 0xEB (password)\r
-       // then write 80 bits of data (or 64 bit data + 16 bit crc if you prefer)\r
-       // finally end with 0x0300 (write frame)\r
-       // all data is sent lsb firts\r
-       // finish with 15ms programming time\r
-\r
-       // modulate antenna\r
-       HIGH(GPIO_SSC_DOUT);\r
-       SpinDelay(50);  // charge time\r
-\r
-       WriteTIbyte(0xbb); // keyword\r
-       WriteTIbyte(0xeb); // password\r
-       WriteTIbyte( (idlo    )&0xff );\r
-       WriteTIbyte( (idlo>>8 )&0xff );\r
-       WriteTIbyte( (idlo>>16)&0xff );\r
-       WriteTIbyte( (idlo>>24)&0xff );\r
-       WriteTIbyte( (idhi    )&0xff );\r
-       WriteTIbyte( (idhi>>8 )&0xff );\r
-       WriteTIbyte( (idhi>>16)&0xff );\r
-       WriteTIbyte( (idhi>>24)&0xff ); // data hi to lo\r
-       WriteTIbyte( (crc     )&0xff ); // crc lo\r
-       WriteTIbyte( (crc>>8  )&0xff ); // crc hi\r
-       WriteTIbyte(0x00); // write frame lo\r
-       WriteTIbyte(0x03); // write frame hi\r
-       HIGH(GPIO_SSC_DOUT);\r
-       SpinDelay(50);  // programming time\r
-\r
-       LED_A_OFF();\r
-\r
-       // get TI tag data into the buffer\r
-       AcquireTiType();\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);\r
-       DbpString("Now use tiread to check");\r
-}\r
-\r
-void SimulateTagLowFrequency(int period, int gap, int ledcontrol)\r
-{\r
-       int i;\r
-       BYTE *tab = (BYTE *)BigBuf;\r
-\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);\r
-\r
-       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT | GPIO_SSC_CLK;\r
-\r
-       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;\r
-       AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_CLK;\r
-\r
-#define SHORT_COIL()   LOW(GPIO_SSC_DOUT)\r
-#define OPEN_COIL()            HIGH(GPIO_SSC_DOUT)\r
-\r
-       i = 0;\r
-       for(;;) {\r
-               while(!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK)) {\r
-                       if(BUTTON_PRESS()) {\r
-                               DbpString("Stopped");\r
-                               return;\r
-                       }\r
-                       WDT_HIT();\r
-               }\r
-\r
-               if (ledcontrol)\r
-                       LED_D_ON();\r
-\r
-               if(tab[i])\r
-                       OPEN_COIL();\r
-               else\r
-                       SHORT_COIL();\r
-\r
-               if (ledcontrol)\r
-                       LED_D_OFF();\r
-\r
-               while(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK) {\r
-                       if(BUTTON_PRESS()) {\r
-                               DbpString("Stopped");\r
-                               return;\r
-                       }\r
-                       WDT_HIT();\r
-               }\r
-\r
-               i++;\r
-               if(i == period) {\r
-                       i = 0;\r
-                       if (gap) { \r
-                               SHORT_COIL();\r
-                               SpinDelayUs(gap);\r
-                       }\r
-               }\r
-       }\r
-}\r
-\r
-/* 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
-        */\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
-       \r
-       AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);\r
-       AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;\r
-       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;\r
-       AT91C_BASE_TC1->TC_CMR =        TC_CMR_TCCLKS_TIMER_CLOCK1 |\r
-                                                               AT91C_TC_ETRGEDG_RISING |\r
-                                                               AT91C_TC_ABETRG |\r
-                                                               AT91C_TC_LDRA_RISING |\r
-                                                               AT91C_TC_LDRB_RISING;\r
-       AT91C_BASE_TC1->TC_CCR =        AT91C_TC_CLKEN |\r
-                                                               AT91C_TC_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(AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {\r
-                       int ra = AT91C_BASE_TC1->TC_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(AT91C_BASE_TC1->TC_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
-                                */ \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(AT91C_BASE_TC1->TC_CV < t0*15);\r
-               OPEN_COIL();\r
-               while(AT91C_BASE_TC1->TC_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(AT91C_BASE_TC1->TC_CV < t0*15);\r
-               SHORT_COIL();\r
-               while(AT91C_BASE_TC1->TC_CV < t0*31);\r
-               LED_B_OFF();\r
-       }\r
-       AT91C_BASE_TC1->TC_CCR = AT91C_TC_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
-       AT91C_BASE_PIOA->PIO_OER = 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
-        */\r
-       while(AT91C_BASE_TC1->TC_CV < t0*(fdt-8));\r
-\r
-       int saved_cmr = AT91C_BASE_TC1->TC_CMR;\r
-       AT91C_BASE_TC1->TC_CMR &= ~AT91C_TC_ETRGEDG; /* Disable external trigger for the clock */\r
-       AT91C_BASE_TC1->TC_CCR = AT91C_TC_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
-       AT91C_BASE_TC1->TC_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
-// compose fc/8 fc/10 waveform\r
-static void fc(int c, int *n) {\r
-       BYTE *dest = (BYTE *)BigBuf;\r
-       int idx;\r
-\r
-       // for when we want an fc8 pattern every 4 logical bits\r
-       if(c==0) {\r
-               dest[((*n)++)]=1;\r
-               dest[((*n)++)]=1;\r
-               dest[((*n)++)]=0;\r
-               dest[((*n)++)]=0;\r
-               dest[((*n)++)]=0;\r
-               dest[((*n)++)]=0;\r
-               dest[((*n)++)]=0;\r
-               dest[((*n)++)]=0;\r
-       }\r
-       //      an fc/8  encoded bit is a bit pattern of  11000000  x6 = 48 samples\r
-       if(c==8) {\r
-               for (idx=0; idx<6; idx++) {\r
-                       dest[((*n)++)]=1;\r
-                       dest[((*n)++)]=1;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-               }\r
-       }\r
-\r
-       //      an fc/10 encoded bit is a bit pattern of 1110000000 x5 = 50 samples\r
-       if(c==10) {\r
-               for (idx=0; idx<5; idx++) {\r
-                       dest[((*n)++)]=1;\r
-                       dest[((*n)++)]=1;\r
-                       dest[((*n)++)]=1;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-                       dest[((*n)++)]=0;\r
-               }\r
-       }\r
-}\r
-\r
-// prepare a waveform pattern in the buffer based on the ID given then\r
-// simulate a HID tag until the button is pressed\r
-void CmdHIDsimTAG(int hi, int lo, int ledcontrol)\r
-{\r
-       int n=0, i=0;\r
-       /*\r
-        HID tag bitstream format\r
-        The tag contains a 44bit unique code. This is sent out MSB first in sets of 4 bits\r
-        A 1 bit is represented as 6 fc8 and 5 fc10 patterns\r
-        A 0 bit is represented as 5 fc10 and 6 fc8 patterns\r
-        A fc8 is inserted before every 4 bits\r
-        A special start of frame pattern is used consisting a0b0 where a and b are neither 0\r
-        nor 1 bits, they are special patterns (a = set of 12 fc8 and b = set of 10 fc10)\r
-       */\r
-\r
-       if (hi>0xFFF) {\r
-               DbpString("Tags can only have 44 bits.");\r
-               return;\r
-       }\r
-       fc(0,&n);\r
-       // special start of frame marker containing invalid bit sequences\r
-       fc(8,  &n);     fc(8,  &n);     // invalid\r
-       fc(8,  &n);     fc(10, &n); // logical 0\r
-       fc(10, &n);     fc(10, &n); // invalid\r
-       fc(8,  &n);     fc(10, &n); // logical 0\r
-\r
-       WDT_HIT();\r
-       // manchester encode bits 43 to 32\r
-       for (i=11; i>=0; i--) {\r
-               if ((i%4)==3) fc(0,&n);\r
-               if ((hi>>i)&1) {\r
-                       fc(10, &n);     fc(8,  &n);             // low-high transition\r
-               } else {\r
-                       fc(8,  &n);     fc(10, &n);             // high-low transition\r
-               }\r
-       }\r
-\r
-       WDT_HIT();\r
-       // manchester encode bits 31 to 0\r
-       for (i=31; i>=0; i--) {\r
-               if ((i%4)==3) fc(0,&n);\r
-               if ((lo>>i)&1) {\r
-                       fc(10, &n);     fc(8,  &n);             // low-high transition\r
-               } else {\r
-                       fc(8,  &n);     fc(10, &n);             // high-low transition\r
-               }\r
-       }\r
-\r
-       if (ledcontrol)\r
-               LED_A_ON();\r
-       SimulateTagLowFrequency(n, 0, ledcontrol);\r
-\r
-       if (ledcontrol)\r
-               LED_A_OFF();\r
-}\r
-\r
-\r
-// loop to capture raw HID waveform then FSK demodulate the TAG ID from it\r
-void CmdHIDdemodFSK(int findone, int *high, int *low, int ledcontrol)\r
-{\r
-       BYTE *dest = (BYTE *)BigBuf;\r
-       int m=0, n=0, i=0, idx=0, found=0, lastval=0;\r
-       DWORD hi=0, lo=0;\r
-\r
-       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz\r
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);\r
-\r
-       // Connect the A/D to the peak-detected low-frequency path.\r
-       SetAdcMuxFor(GPIO_MUXSEL_LOPKD);\r
-\r
-       // Give it a bit of time for the resonant antenna to settle.\r
-       SpinDelay(50);\r
-\r
-       // Now set up the SSC to get the ADC samples that are now streaming at us.\r
-       FpgaSetupSsc();\r
-\r
-       for(;;) {\r
-               WDT_HIT();\r
-               if (ledcontrol)\r
-                       LED_A_ON();\r
-               if(BUTTON_PRESS()) {\r
-                       DbpString("Stopped");\r
-                       if (ledcontrol)\r
-                               LED_A_OFF();\r
-                       return;\r
-               }\r
-\r
-               i = 0;\r
-               m = sizeof(BigBuf);\r
-               memset(dest,128,m);\r
-               for(;;) {\r
-                       if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {\r
-                               AT91C_BASE_SSC->SSC_THR = 0x43;\r
-                               if (ledcontrol)\r
-                                       LED_D_ON();\r
-                       }\r
-                       if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {\r
-                               dest[i] = (BYTE)AT91C_BASE_SSC->SSC_RHR;\r
-                               // we don't care about actual value, only if it's more or less than a\r
-                               // threshold essentially we capture zero crossings for later analysis\r
-                               if(dest[i] < 127) dest[i] = 0; else dest[i] = 1;\r
-                               i++;\r
-                               if (ledcontrol)\r
-                                       LED_D_OFF();\r
-                               if(i >= m) {\r
-                                       break;\r
-                               }\r
-                       }\r
-               }\r
-\r
-               // FSK demodulator\r
-\r
-               // sync to first lo-hi transition\r
-               for( idx=1; idx<m; idx++) {\r
-                       if (dest[idx-1]<dest[idx])\r
-                               lastval=idx;\r
-                               break;\r
-               }\r
-               WDT_HIT();\r
-\r
-               // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)\r
-               // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere\r
-               // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10\r
-               for( i=0; idx<m; idx++) {\r
-                       if (dest[idx-1]<dest[idx]) {\r
-                               dest[i]=idx-lastval;\r
-                               if (dest[i] <= 8) {\r
-                                               dest[i]=1;\r
-                               } else {\r
-                                               dest[i]=0;\r
-                               }\r
-\r
-                               lastval=idx;\r
-                               i++;\r
-                       }\r
-               }\r
-               m=i;\r
-               WDT_HIT();\r
-\r
-               // we now have a set of cycle counts, loop over previous results and aggregate data into bit patterns\r
-               lastval=dest[0];\r
-               idx=0;\r
-               i=0;\r
-               n=0;\r
-               for( idx=0; idx<m; idx++) {\r
-                       if (dest[idx]==lastval) {\r
-                               n++;\r
-                       } else {\r
-                               // a bit time is five fc/10 or six fc/8 cycles so figure out how many bits a pattern width represents,\r
-                               // an extra fc/8 pattern preceeds every 4 bits (about 200 cycles) just to complicate things but it gets\r
-                               // swallowed up by rounding\r
-                               // expected results are 1 or 2 bits, any more and it's an invalid manchester encoding\r
-                               // special start of frame markers use invalid manchester states (no transitions) by using sequences\r
-                               // like 111000\r
-                               if (dest[idx-1]) {\r
-                                       n=(n+1)/6;                      // fc/8 in sets of 6\r
-                               } else {\r
-                                       n=(n+1)/5;                      // fc/10 in sets of 5\r
-                               }\r
-                               switch (n) {                    // stuff appropriate bits in buffer\r
-                                       case 0:\r
-                                       case 1: // one bit\r
-                                               dest[i++]=dest[idx-1];\r
-                                               break;\r
-                                       case 2: // two bits\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               break;\r
-                                       case 3: // 3 bit start of frame markers\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               break;\r
-                                       // When a logic 0 is immediately followed by the start of the next transmisson\r
-                                       // (special pattern) a pattern of 4 bit duration lengths is created.\r
-                                       case 4:\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               dest[i++]=dest[idx-1];\r
-                                               break;\r
-                                       default:        // this shouldn't happen, don't stuff any bits\r
-                                               break;\r
-                               }\r
-                               n=0;\r
-                               lastval=dest[idx];\r
-                       }\r
-               }\r
-               m=i;\r
-               WDT_HIT();\r
-\r
-               // final loop, go over previously decoded manchester data and decode into usable tag ID\r
-               // 111000 bit pattern represent start of frame, 01 pattern represents a 1 and 10 represents a 0\r
-               for( idx=0; idx<m-6; idx++) {\r
-                       // search for a start of frame marker\r
-                       if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )\r
-                       {\r
-                               found=1;\r
-                               idx+=6;\r
-                               if (found && (hi|lo)) {\r
-                                       Dbprintf("TAG ID: %x%08x (%d)",\r
-                                               (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);\r
-                                       /* if we're only looking for one tag */\r
-                                       if (findone)\r
-                                       {\r
-                                               *high = hi;\r
-                                               *low = lo;\r
-                                               return;\r
-                                       }\r
-                                       hi=0;\r
-                                       lo=0;\r
-                                       found=0;\r
-                               }\r
-                       }\r
-                       if (found) {\r
-                               if (dest[idx] && (!dest[idx+1]) ) {\r
-                                       hi=(hi<<1)|(lo>>31);\r
-                                       lo=(lo<<1)|0;\r
-                               } else if ( (!dest[idx]) && dest[idx+1]) {\r
-                                       hi=(hi<<1)|(lo>>31);\r
-                                       lo=(lo<<1)|1;\r
-                               } else {\r
-                                       found=0;\r
-                                       hi=0;\r
-                                       lo=0;\r
-                               }\r
-                               idx++;\r
-                       }\r
-                       if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )\r
-                       {\r
-                               found=1;\r
-                               idx+=6;\r
-                               if (found && (hi|lo)) {\r
-                                       Dbprintf("TAG ID: %x%08x (%d)",\r
-                                               (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);\r
-                                       /* if we're only looking for one tag */\r
-                                       if (findone)\r
-                                       {\r
-                                               *high = hi;\r
-                                               *low = lo;\r
-                                               return;\r
-                                       }\r
-                                       hi=0;\r
-                                       lo=0;\r
-                                       found=0;\r
-                               }\r
-                       }\r
-               }\r
-               WDT_HIT();\r
-       }\r
-}\r
+//-----------------------------------------------------------------------------
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// Miscellaneous routines for low frequency tag operations.
+// Tags supported here so far are Texas Instruments (TI), HID
+// Also routines for raw mode reading/simulating of LF waveform
+//-----------------------------------------------------------------------------
+
+#include "proxmark3.h"
+#include "apps.h"
+#include "util.h"
+#include "hitag2.h"
+#include "crc16.h"
+#include "string.h"
+
+void AcquireRawAdcSamples125k(int at134khz)
+{
+       if (at134khz)
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+       else
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+
+       // Connect the A/D to the peak-detected low-frequency path.
+       SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
+
+       // Give it a bit of time for the resonant antenna to settle.
+       SpinDelay(50);
+
+       // Now set up the SSC to get the ADC samples that are now streaming at us.
+       FpgaSetupSsc();
+
+       // Now call the acquisition routine
+       DoAcquisition125k();
+}
+
+// split into two routines so we can avoid timing issues after sending commands //
+void DoAcquisition125k(void)
+{
+       uint8_t *dest = (uint8_t *)BigBuf;
+       int n = sizeof(BigBuf);
+       int i;
+
+       memset(dest, 0, n);
+       i = 0;
+       for(;;) {
+               if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
+                       AT91C_BASE_SSC->SSC_THR = 0x43;
+                       LED_D_ON();
+               }
+               if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
+                       dest[i] = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+                       i++;
+                       LED_D_OFF();
+                       if (i >= n) break;
+               }
+       }
+       Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",
+                       dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);
+}
+
+void ModThenAcquireRawAdcSamples125k(int delay_off, int period_0, int period_1, uint8_t *command)
+{
+       int at134khz;
+
+       /* Make sure the tag is reset */
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       SpinDelay(2500);
+
+       // see if 'h' was specified
+       if (command[strlen((char *) command) - 1] == 'h')
+               at134khz = TRUE;
+       else
+               at134khz = FALSE;
+
+       if (at134khz)
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+       else
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+
+       // Give it a bit of time for the resonant antenna to settle.
+       SpinDelay(50);
+       // And a little more time for the tag to fully power up
+       SpinDelay(2000);
+
+       // Now set up the SSC to get the ADC samples that are now streaming at us.
+       FpgaSetupSsc();
+
+       // now modulate the reader field
+       while(*command != '\0' && *command != ' ') {
+               FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+               LED_D_OFF();
+               SpinDelayUs(delay_off);
+               if (at134khz)
+                       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+               else
+                       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+
+               FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+               LED_D_ON();
+               if(*(command++) == '0')
+                       SpinDelayUs(period_0);
+               else
+                       SpinDelayUs(period_1);
+       }
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LED_D_OFF();
+       SpinDelayUs(delay_off);
+       if (at134khz)
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+       else
+               FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+
+       // now do the read
+       DoAcquisition125k();
+}
+
+/* blank r/w tag data stream
+...0000000000000000 01111111
+1010101010101010101010101010101010101010101010101010101010101010
+0011010010100001
+01111111
+101010101010101[0]000...
+
+[5555fe852c5555555555555555fe0000]
+*/
+void ReadTItag(void)
+{
+       // some hardcoded initial params
+       // when we read a TI tag we sample the zerocross line at 2Mhz
+       // TI tags modulate a 1 as 16 cycles of 123.2Khz
+       // TI tags modulate a 0 as 16 cycles of 134.2Khz
+       #define FSAMPLE 2000000
+       #define FREQLO 123200
+       #define FREQHI 134200
+
+       signed char *dest = (signed char *)BigBuf;
+       int n = sizeof(BigBuf);
+//     int *dest = GraphBuffer;
+//     int n = GraphTraceLen;
+
+       // 128 bit shift register [shift3:shift2:shift1:shift0]
+       uint32_t shift3 = 0, shift2 = 0, shift1 = 0, shift0 = 0;
+
+       int i, cycles=0, samples=0;
+       // how many sample points fit in 16 cycles of each frequency
+       uint32_t sampleslo = (FSAMPLE<<4)/FREQLO, sampleshi = (FSAMPLE<<4)/FREQHI;
+       // when to tell if we're close enough to one freq or another
+       uint32_t threshold = (sampleslo - sampleshi + 1)>>1;
+
+       // TI tags charge at 134.2Khz
+       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+
+       // Place FPGA in passthrough mode, in this mode the CROSS_LO line
+       // connects to SSP_DIN and the SSP_DOUT logic level controls
+       // whether we're modulating the antenna (high)
+       // or listening to the antenna (low)
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);
+
+       // get TI tag data into the buffer
+       AcquireTiType();
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+
+       for (i=0; i<n-1; i++) {
+               // count cycles by looking for lo to hi zero crossings
+               if ( (dest[i]<0) && (dest[i+1]>0) ) {
+                       cycles++;
+                       // after 16 cycles, measure the frequency
+                       if (cycles>15) {
+                               cycles=0;
+                               samples=i-samples; // number of samples in these 16 cycles
+
+                               // TI bits are coming to us lsb first so shift them
+                               // right through our 128 bit right shift register
+                         shift0 = (shift0>>1) | (shift1 << 31);
+                         shift1 = (shift1>>1) | (shift2 << 31);
+                         shift2 = (shift2>>1) | (shift3 << 31);
+                         shift3 >>= 1;
+
+                               // check if the cycles fall close to the number
+                               // expected for either the low or high frequency
+                               if ( (samples>(sampleslo-threshold)) && (samples<(sampleslo+threshold)) ) {
+                                       // low frequency represents a 1
+                                       shift3 |= (1<<31);
+                               } else if ( (samples>(sampleshi-threshold)) && (samples<(sampleshi+threshold)) ) {
+                                       // high frequency represents a 0
+                               } else {
+                                       // probably detected a gay waveform or noise
+                                       // use this as gaydar or discard shift register and start again
+                                       shift3 = shift2 = shift1 = shift0 = 0;
+                               }
+                               samples = i;
+
+                               // for each bit we receive, test if we've detected a valid tag
+
+                               // if we see 17 zeroes followed by 6 ones, we might have a tag
+                               // remember the bits are backwards
+                               if ( ((shift0 & 0x7fffff) == 0x7e0000) ) {
+                                       // if start and end bytes match, we have a tag so break out of the loop
+                                       if ( ((shift0>>16)&0xff) == ((shift3>>8)&0xff) ) {
+                                               cycles = 0xF0B; //use this as a flag (ugly but whatever)
+                                               break;
+                                       }
+                               }
+                       }
+               }
+       }
+
+       // if flag is set we have a tag
+       if (cycles!=0xF0B) {
+               DbpString("Info: No valid tag detected.");
+       } else {
+         // 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;
+
+               // if r/w tag, check ident match
+               if ( shift3&(1<<15) ) {
+                       DbpString("Info: TI tag is rewriteable");
+                       // only 15 bits compare, last bit of ident is not valid
+                       if ( ((shift3>>16)^shift0)&0x7fff ) {
+                               DbpString("Error: Ident mismatch!");
+                       } else {
+                               DbpString("Info: TI tag ident is valid");
+                       }
+               } else {
+                       DbpString("Info: TI tag is readonly");
+               }
+
+               // WARNING the order of the bytes in which we calc crc below needs checking
+               // i'm 99% sure the crc algorithm is correct, but it may need to eat the
+               // bytes in reverse or something
+               // calculate CRC
+               uint32_t 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);
+
+               Dbprintf("Info: Tag data: %x%08x, crc=%x",
+                       (unsigned int)shift1, (unsigned int)shift0, (unsigned int)shift2 & 0xFFFF);
+               if (crc != (shift2&0xffff)) {
+                       Dbprintf("Error: CRC mismatch, expected %x", (unsigned int)crc);
+               } else {
+                       DbpString("Info: CRC is good");
+               }
+       }
+}
+
+void WriteTIbyte(uint8_t b)
+{
+       int i = 0;
+
+       // modulate 8 bits out to the antenna
+       for (i=0; i<8; i++)
+       {
+               if (b&(1<<i)) {
+                       // stop modulating antenna
+                       LOW(GPIO_SSC_DOUT);
+                       SpinDelayUs(1000);
+                       // modulate antenna
+                       HIGH(GPIO_SSC_DOUT);
+                       SpinDelayUs(1000);
+               } else {
+                       // stop modulating antenna
+                       LOW(GPIO_SSC_DOUT);
+                       SpinDelayUs(300);
+                       // modulate antenna
+                       HIGH(GPIO_SSC_DOUT);
+                       SpinDelayUs(1700);
+               }
+       }
+}
+
+void AcquireTiType(void)
+{
+       int i, j, n;
+       // tag transmission is <20ms, sampling at 2M gives us 40K samples max
+       // each sample is 1 bit stuffed into a uint32_t so we need 1250 uint32_t
+       #define TIBUFLEN 1250
+
+       // clear buffer
+       memset(BigBuf,0,sizeof(BigBuf));
+
+       // Set up the synchronous serial port
+       AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DIN;
+       AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN;
+
+       // steal this pin from the SSP and use it to control the modulation
+       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
+       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+
+       AT91C_BASE_SSC->SSC_CR = AT91C_SSC_SWRST;
+       AT91C_BASE_SSC->SSC_CR = AT91C_SSC_RXEN | AT91C_SSC_TXEN;
+
+       // Sample at 2 Mbit/s, so TI tags are 16.2 vs. 14.9 clocks long
+       // 48/2 = 24 MHz clock must be divided by 12
+       AT91C_BASE_SSC->SSC_CMR = 12;
+
+       AT91C_BASE_SSC->SSC_RCMR = SSC_CLOCK_MODE_SELECT(0);
+       AT91C_BASE_SSC->SSC_RFMR = SSC_FRAME_MODE_BITS_IN_WORD(32) | AT91C_SSC_MSBF;
+       AT91C_BASE_SSC->SSC_TCMR = 0;
+       AT91C_BASE_SSC->SSC_TFMR = 0;
+
+       LED_D_ON();
+
+       // modulate antenna
+       HIGH(GPIO_SSC_DOUT);
+
+       // Charge TI tag for 50ms.
+       SpinDelay(50);
+
+       // stop modulating antenna and listen
+       LOW(GPIO_SSC_DOUT);
+
+       LED_D_OFF();
+
+       i = 0;
+       for(;;) {
+               if(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
+                       BigBuf[i] = AT91C_BASE_SSC->SSC_RHR;    // store 32 bit values in buffer
+                       i++; if(i >= TIBUFLEN) break;
+               }
+               WDT_HIT();
+       }
+
+       // return stolen pin to SSP
+       AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DOUT;
+       AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN | GPIO_SSC_DOUT;
+
+       char *dest = (char *)BigBuf;
+       n = TIBUFLEN*32;
+       // unpack buffer
+       for (i=TIBUFLEN-1; i>=0; i--) {
+               for (j=0; j<32; j++) {
+                       if(BigBuf[i] & (1 << j)) {
+                               dest[--n] = 1;
+                       } else {
+                               dest[--n] = -1;
+                       }
+               }
+       }
+}
+
+// arguments: 64bit data split into 32bit idhi:idlo and optional 16bit crc
+// if crc provided, it will be written with the data verbatim (even if bogus)
+// if not provided a valid crc will be computed from the data and written.
+void WriteTItag(uint32_t idhi, uint32_t idlo, uint16_t crc)
+{
+       if(crc == 0) {
+               crc = update_crc16(crc, (idlo)&0xff);
+               crc = update_crc16(crc, (idlo>>8)&0xff);
+               crc = update_crc16(crc, (idlo>>16)&0xff);
+               crc = update_crc16(crc, (idlo>>24)&0xff);
+               crc = update_crc16(crc, (idhi)&0xff);
+               crc = update_crc16(crc, (idhi>>8)&0xff);
+               crc = update_crc16(crc, (idhi>>16)&0xff);
+               crc = update_crc16(crc, (idhi>>24)&0xff);
+       }
+       Dbprintf("Writing to tag: %x%08x, crc=%x",
+               (unsigned int) idhi, (unsigned int) idlo, crc);
+
+       // TI tags charge at 134.2Khz
+       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+       // Place FPGA in passthrough mode, in this mode the CROSS_LO line
+       // connects to SSP_DIN and the SSP_DOUT logic level controls
+       // whether we're modulating the antenna (high)
+       // or listening to the antenna (low)
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);
+       LED_A_ON();
+
+       // steal this pin from the SSP and use it to control the modulation
+       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
+       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+
+       // writing algorithm:
+       // a high bit consists of a field off for 1ms and field on for 1ms
+       // a low bit consists of a field off for 0.3ms and field on for 1.7ms
+       // initiate a charge time of 50ms (field on) then immediately start writing bits
+       // start by writing 0xBB (keyword) and 0xEB (password)
+       // then write 80 bits of data (or 64 bit data + 16 bit crc if you prefer)
+       // finally end with 0x0300 (write frame)
+       // all data is sent lsb firts
+       // finish with 15ms programming time
+
+       // modulate antenna
+       HIGH(GPIO_SSC_DOUT);
+       SpinDelay(50);  // charge time
+
+       WriteTIbyte(0xbb); // keyword
+       WriteTIbyte(0xeb); // password
+       WriteTIbyte( (idlo    )&0xff );
+       WriteTIbyte( (idlo>>8 )&0xff );
+       WriteTIbyte( (idlo>>16)&0xff );
+       WriteTIbyte( (idlo>>24)&0xff );
+       WriteTIbyte( (idhi    )&0xff );
+       WriteTIbyte( (idhi>>8 )&0xff );
+       WriteTIbyte( (idhi>>16)&0xff );
+       WriteTIbyte( (idhi>>24)&0xff ); // data hi to lo
+       WriteTIbyte( (crc     )&0xff ); // crc lo
+       WriteTIbyte( (crc>>8  )&0xff ); // crc hi
+       WriteTIbyte(0x00); // write frame lo
+       WriteTIbyte(0x03); // write frame hi
+       HIGH(GPIO_SSC_DOUT);
+       SpinDelay(50);  // programming time
+
+       LED_A_OFF();
+
+       // get TI tag data into the buffer
+       AcquireTiType();
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       DbpString("Now use tiread to check");
+}
+
+void SimulateTagLowFrequency(int period, int gap, int ledcontrol)
+{
+       int i;
+       uint8_t *tab = (uint8_t *)BigBuf;
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);
+
+       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT | GPIO_SSC_CLK;
+
+       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+       AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_CLK;
+
+#define SHORT_COIL()   LOW(GPIO_SSC_DOUT)
+#define OPEN_COIL()            HIGH(GPIO_SSC_DOUT)
+
+       i = 0;
+       for(;;) {
+               while(!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK)) {
+                       if(BUTTON_PRESS()) {
+                               DbpString("Stopped");
+                               return;
+                       }
+                       WDT_HIT();
+               }
+
+               if (ledcontrol)
+                       LED_D_ON();
+
+               if(tab[i])
+                       OPEN_COIL();
+               else
+                       SHORT_COIL();
+
+               if (ledcontrol)
+                       LED_D_OFF();
+
+               while(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK) {
+                       if(BUTTON_PRESS()) {
+                               DbpString("Stopped");
+                               return;
+                       }
+                       WDT_HIT();
+               }
+
+               i++;
+               if(i == period) {
+                       i = 0;
+                       if (gap) {
+                               SHORT_COIL();
+                               SpinDelayUs(gap);
+                       }
+               }
+       }
+}
+
+/* Provides a framework for bidirectional LF tag communication
+ * Encoding is currently Hitag2, but the general idea can probably
+ * be transferred to other encodings.
+ *
+ * The new FPGA code will, for the LF simulator mode, give on SSC_FRAME
+ * (PA15) a thresholded version of the signal from the ADC. Setting the
+ * ADC path to the low frequency peak detection signal, will enable a
+ * somewhat reasonable receiver for modulation on the carrier signal
+ * that is generated by the reader. The signal is low when the reader
+ * field is switched off, and high when the reader field is active. Due
+ * to the way that the signal looks like, mostly only the rising edge is
+ * useful, your mileage may vary.
+ *
+ * Neat perk: PA15 can not only be used as a bit-banging GPIO, but is also
+ * TIOA1, which can be used as the capture input for timer 1. This should
+ * make it possible to measure the exact edge-to-edge time, without processor
+ * intervention.
+ *
+ * Arguments: divisor is the divisor to be sent to the FPGA (e.g. 95 for 125kHz)
+ * t0 is the carrier frequency cycle duration in terms of MCK (384 for 125kHz)
+ *
+ * The following defines are in carrier periods:
+ */
+#define HITAG_T_0_MIN 15 /* T[0] should be 18..22 */
+#define HITAG_T_1_MIN 24 /* T[1] should be 26..30 */
+#define HITAG_T_EOF   40 /* T_EOF should be > 36 */
+#define HITAG_T_WRESP 208 /* T_wresp should be 204..212 */
+
+static void hitag_handle_frame(int t0, int frame_len, char *frame);
+//#define DEBUG_RA_VALUES 1
+#define DEBUG_FRAME_CONTENTS 1
+void SimulateTagLowFrequencyBidir(int divisor, int t0)
+{
+#if DEBUG_RA_VALUES || DEBUG_FRAME_CONTENTS
+       int i = 0;
+#endif
+       char frame[10];
+       int frame_pos=0;
+
+       DbpString("Starting Hitag2 emulator, press button to end");
+       hitag2_init();
+
+       /* Set up simulator mode, frequency divisor which will drive the FPGA
+        * and analog mux selection.
+        */
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);
+       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);
+       SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
+       RELAY_OFF();
+
+       /* Set up Timer 1:
+        * Capture mode, timer source MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
+        * external trigger rising edge, load RA on rising edge of TIOA, load RB on rising
+        * edge of TIOA. Assign PA15 to TIOA1 (peripheral B)
+        */
+
+       AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
+       AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
+       AT91C_BASE_TC1->TC_CMR =        AT91C_TC_CLKS_TIMER_DIV1_CLOCK |
+                                                               AT91C_TC_ETRGEDG_RISING |
+                                                               AT91C_TC_ABETRG |
+                                                               AT91C_TC_LDRA_RISING |
+                                                               AT91C_TC_LDRB_RISING;
+       AT91C_BASE_TC1->TC_CCR =        AT91C_TC_CLKEN |
+                                                               AT91C_TC_SWTRG;
+
+       /* calculate the new value for the carrier period in terms of TC1 values */
+       t0 = t0/2;
+
+       int overflow = 0;
+       while(!BUTTON_PRESS()) {
+               WDT_HIT();
+               if(AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
+                       int ra = AT91C_BASE_TC1->TC_RA;
+                       if((ra > t0*HITAG_T_EOF) | overflow) ra = t0*HITAG_T_EOF+1;
+#if DEBUG_RA_VALUES
+                       if(ra > 255 || overflow) ra = 255;
+                       ((char*)BigBuf)[i] = ra;
+                       i = (i+1) % 8000;
+#endif
+
+                       if(overflow || (ra > t0*HITAG_T_EOF) || (ra < t0*HITAG_T_0_MIN)) {
+                               /* Ignore */
+                       } else if(ra >= t0*HITAG_T_1_MIN ) {
+                               /* '1' bit */
+                               if(frame_pos < 8*sizeof(frame)) {
+                                       frame[frame_pos / 8] |= 1<<( 7-(frame_pos%8) );
+                                       frame_pos++;
+                               }
+                       } else if(ra >= t0*HITAG_T_0_MIN) {
+                               /* '0' bit */
+                               if(frame_pos < 8*sizeof(frame)) {
+                                       frame[frame_pos / 8] |= 0<<( 7-(frame_pos%8) );
+                                       frame_pos++;
+                               }
+                       }
+
+                       overflow = 0;
+                       LED_D_ON();
+               } else {
+                       if(AT91C_BASE_TC1->TC_CV > t0*HITAG_T_EOF) {
+                               /* Minor nuisance: In Capture mode, the timer can not be
+                                * stopped by a Compare C. There's no way to stop the clock
+                                * in software, so we'll just have to note the fact that an
+                                * overflow happened and the next loaded timer value might
+                                * have wrapped. Also, this marks the end of frame, and the
+                                * still running counter can be used to determine the correct
+                                * time for the start of the reply.
+                                */
+                               overflow = 1;
+
+                               if(frame_pos > 0) {
+                                       /* Have a frame, do something with it */
+#if DEBUG_FRAME_CONTENTS
+                                       ((char*)BigBuf)[i++] = frame_pos;
+                                       memcpy( ((char*)BigBuf)+i, frame, 7);
+                                       i+=7;
+                                       i = i % sizeof(BigBuf);
+#endif
+                                       hitag_handle_frame(t0, frame_pos, frame);
+                                       memset(frame, 0, sizeof(frame));
+                               }
+                               frame_pos = 0;
+
+                       }
+                       LED_D_OFF();
+               }
+       }
+       DbpString("All done");
+}
+
+static void hitag_send_bit(int t0, int bit) {
+       if(bit == 1) {
+               /* Manchester: Loaded, then unloaded */
+               LED_A_ON();
+               SHORT_COIL();
+               while(AT91C_BASE_TC1->TC_CV < t0*15);
+               OPEN_COIL();
+               while(AT91C_BASE_TC1->TC_CV < t0*31);
+               LED_A_OFF();
+       } else if(bit == 0) {
+               /* Manchester: Unloaded, then loaded */
+               LED_B_ON();
+               OPEN_COIL();
+               while(AT91C_BASE_TC1->TC_CV < t0*15);
+               SHORT_COIL();
+               while(AT91C_BASE_TC1->TC_CV < t0*31);
+               LED_B_OFF();
+       }
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG; /* Reset clock for the next bit */
+
+}
+static void hitag_send_frame(int t0, int frame_len, const char const * frame, int fdt)
+{
+       OPEN_COIL();
+       AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+
+       /* Wait for HITAG_T_WRESP carrier periods after the last reader bit,
+        * not that since the clock counts since the rising edge, but T_wresp is
+        * with respect to the falling edge, we need to wait actually (T_wresp - T_g)
+        * periods. The gap time T_g varies (4..10).
+        */
+       while(AT91C_BASE_TC1->TC_CV < t0*(fdt-8));
+
+       int saved_cmr = AT91C_BASE_TC1->TC_CMR;
+       AT91C_BASE_TC1->TC_CMR &= ~AT91C_TC_ETRGEDG; /* Disable external trigger for the clock */
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG; /* Reset the clock and use it for response timing */
+
+       int i;
+       for(i=0; i<5; i++)
+               hitag_send_bit(t0, 1); /* Start of frame */
+
+       for(i=0; i<frame_len; i++) {
+               hitag_send_bit(t0, !!(frame[i/ 8] & (1<<( 7-(i%8) ))) );
+       }
+
+       OPEN_COIL();
+       AT91C_BASE_TC1->TC_CMR = saved_cmr;
+}
+
+/* Callback structure to cleanly separate tag emulation code from the radio layer. */
+static int hitag_cb(const char* response_data, const int response_length, const int fdt, void *cb_cookie)
+{
+       hitag_send_frame(*(int*)cb_cookie, response_length, response_data, fdt);
+       return 0;
+}
+/* Frame length in bits, frame contents in MSBit first format */
+static void hitag_handle_frame(int t0, int frame_len, char *frame)
+{
+       hitag2_handle_command(frame, frame_len, hitag_cb, &t0);
+}
+
+// compose fc/8 fc/10 waveform
+static void fc(int c, int *n) {
+       uint8_t *dest = (uint8_t *)BigBuf;
+       int idx;
+
+       // for when we want an fc8 pattern every 4 logical bits
+       if(c==0) {
+               dest[((*n)++)]=1;
+               dest[((*n)++)]=1;
+               dest[((*n)++)]=0;
+               dest[((*n)++)]=0;
+               dest[((*n)++)]=0;
+               dest[((*n)++)]=0;
+               dest[((*n)++)]=0;
+               dest[((*n)++)]=0;
+       }
+       //      an fc/8  encoded bit is a bit pattern of  11000000  x6 = 48 samples
+       if(c==8) {
+               for (idx=0; idx<6; idx++) {
+                       dest[((*n)++)]=1;
+                       dest[((*n)++)]=1;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+               }
+       }
+
+       //      an fc/10 encoded bit is a bit pattern of 1110000000 x5 = 50 samples
+       if(c==10) {
+               for (idx=0; idx<5; idx++) {
+                       dest[((*n)++)]=1;
+                       dest[((*n)++)]=1;
+                       dest[((*n)++)]=1;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+                       dest[((*n)++)]=0;
+               }
+       }
+}
+
+// prepare a waveform pattern in the buffer based on the ID given then
+// simulate a HID tag until the button is pressed
+void CmdHIDsimTAG(int hi, int lo, int ledcontrol)
+{
+       int n=0, i=0;
+       /*
+        HID tag bitstream format
+        The tag contains a 44bit unique code. This is sent out MSB first in sets of 4 bits
+        A 1 bit is represented as 6 fc8 and 5 fc10 patterns
+        A 0 bit is represented as 5 fc10 and 6 fc8 patterns
+        A fc8 is inserted before every 4 bits
+        A special start of frame pattern is used consisting a0b0 where a and b are neither 0
+        nor 1 bits, they are special patterns (a = set of 12 fc8 and b = set of 10 fc10)
+       */
+
+       if (hi>0xFFF) {
+               DbpString("Tags can only have 44 bits.");
+               return;
+       }
+       fc(0,&n);
+       // special start of frame marker containing invalid bit sequences
+       fc(8,  &n);     fc(8,  &n);     // invalid
+       fc(8,  &n);     fc(10, &n); // logical 0
+       fc(10, &n);     fc(10, &n); // invalid
+       fc(8,  &n);     fc(10, &n); // logical 0
+
+       WDT_HIT();
+       // manchester encode bits 43 to 32
+       for (i=11; i>=0; i--) {
+               if ((i%4)==3) fc(0,&n);
+               if ((hi>>i)&1) {
+                       fc(10, &n);     fc(8,  &n);             // low-high transition
+               } else {
+                       fc(8,  &n);     fc(10, &n);             // high-low transition
+               }
+       }
+
+       WDT_HIT();
+       // manchester encode bits 31 to 0
+       for (i=31; i>=0; i--) {
+               if ((i%4)==3) fc(0,&n);
+               if ((lo>>i)&1) {
+                       fc(10, &n);     fc(8,  &n);             // low-high transition
+               } else {
+                       fc(8,  &n);     fc(10, &n);             // high-low transition
+               }
+       }
+
+       if (ledcontrol)
+               LED_A_ON();
+       SimulateTagLowFrequency(n, 0, ledcontrol);
+
+       if (ledcontrol)
+               LED_A_OFF();
+}
+
+
+// loop to capture raw HID waveform then FSK demodulate the TAG ID from it
+void CmdHIDdemodFSK(int findone, int *high, int *low, int ledcontrol)
+{
+       uint8_t *dest = (uint8_t *)BigBuf;
+       int m=0, n=0, i=0, idx=0, found=0, lastval=0;
+       uint32_t hi=0, lo=0;
+
+       FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+
+       // Connect the A/D to the peak-detected low-frequency path.
+       SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
+
+       // Give it a bit of time for the resonant antenna to settle.
+       SpinDelay(50);
+
+       // Now set up the SSC to get the ADC samples that are now streaming at us.
+       FpgaSetupSsc();
+
+       for(;;) {
+               WDT_HIT();
+               if (ledcontrol)
+                       LED_A_ON();
+               if(BUTTON_PRESS()) {
+                       DbpString("Stopped");
+                       if (ledcontrol)
+                               LED_A_OFF();
+                       return;
+               }
+
+               i = 0;
+               m = sizeof(BigBuf);
+               memset(dest,128,m);
+               for(;;) {
+                       if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                               AT91C_BASE_SSC->SSC_THR = 0x43;
+                               if (ledcontrol)
+                                       LED_D_ON();
+                       }
+                       if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                               dest[i] = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+                               // we don't care about actual value, only if it's more or less than a
+                               // threshold essentially we capture zero crossings for later analysis
+                               if(dest[i] < 127) dest[i] = 0; else dest[i] = 1;
+                               i++;
+                               if (ledcontrol)
+                                       LED_D_OFF();
+                               if(i >= m) {
+                                       break;
+                               }
+                       }
+               }
+
+               // FSK demodulator
+
+               // sync to first lo-hi transition
+               for( idx=1; idx<m; idx++) {
+                       if (dest[idx-1]<dest[idx])
+                               lastval=idx;
+                               break;
+               }
+               WDT_HIT();
+
+               // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
+               // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere
+               // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
+               for( i=0; idx<m; idx++) {
+                       if (dest[idx-1]<dest[idx]) {
+                               dest[i]=idx-lastval;
+                               if (dest[i] <= 8) {
+                                               dest[i]=1;
+                               } else {
+                                               dest[i]=0;
+                               }
+
+                               lastval=idx;
+                               i++;
+                       }
+               }
+               m=i;
+               WDT_HIT();
+
+               // we now have a set of cycle counts, loop over previous results and aggregate data into bit patterns
+               lastval=dest[0];
+               idx=0;
+               i=0;
+               n=0;
+               for( idx=0; idx<m; idx++) {
+                       if (dest[idx]==lastval) {
+                               n++;
+                       } else {
+                               // a bit time is five fc/10 or six fc/8 cycles so figure out how many bits a pattern width represents,
+                               // an extra fc/8 pattern preceeds every 4 bits (about 200 cycles) just to complicate things but it gets
+                               // swallowed up by rounding
+                               // expected results are 1 or 2 bits, any more and it's an invalid manchester encoding
+                               // special start of frame markers use invalid manchester states (no transitions) by using sequences
+                               // like 111000
+                               if (dest[idx-1]) {
+                                       n=(n+1)/6;                      // fc/8 in sets of 6
+                               } else {
+                                       n=(n+1)/5;                      // fc/10 in sets of 5
+                               }
+                               switch (n) {                    // stuff appropriate bits in buffer
+                                       case 0:
+                                       case 1: // one bit
+                                               dest[i++]=dest[idx-1];
+                                               break;
+                                       case 2: // two bits
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               break;
+                                       case 3: // 3 bit start of frame markers
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               break;
+                                       // When a logic 0 is immediately followed by the start of the next transmisson
+                                       // (special pattern) a pattern of 4 bit duration lengths is created.
+                                       case 4:
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               dest[i++]=dest[idx-1];
+                                               break;
+                                       default:        // this shouldn't happen, don't stuff any bits
+                                               break;
+                               }
+                               n=0;
+                               lastval=dest[idx];
+                       }
+               }
+               m=i;
+               WDT_HIT();
+
+               // final loop, go over previously decoded manchester data and decode into usable tag ID
+               // 111000 bit pattern represent start of frame, 01 pattern represents a 1 and 10 represents a 0
+               for( idx=0; idx<m-6; idx++) {
+                       // search for a start of frame marker
+                       if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )
+                       {
+                               found=1;
+                               idx+=6;
+                               if (found && (hi|lo)) {
+                                       Dbprintf("TAG ID: %x%08x (%d)",
+                                               (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);
+                                       /* if we're only looking for one tag */
+                                       if (findone)
+                                       {
+                                               *high = hi;
+                                               *low = lo;
+                                               return;
+                                       }
+                                       hi=0;
+                                       lo=0;
+                                       found=0;
+                               }
+                       }
+                       if (found) {
+                               if (dest[idx] && (!dest[idx+1]) ) {
+                                       hi=(hi<<1)|(lo>>31);
+                                       lo=(lo<<1)|0;
+                               } else if ( (!dest[idx]) && dest[idx+1]) {
+                                       hi=(hi<<1)|(lo>>31);
+                                       lo=(lo<<1)|1;
+                               } else {
+                                       found=0;
+                                       hi=0;
+                                       lo=0;
+                               }
+                               idx++;
+                       }
+                       if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )
+                       {
+                               found=1;
+                               idx+=6;
+                               if (found && (hi|lo)) {
+                                       Dbprintf("TAG ID: %x%08x (%d)",
+                                               (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);
+                                       /* if we're only looking for one tag */
+                                       if (findone)
+                                       {
+                                               *high = hi;
+                                               *low = lo;
+                                               return;
+                                       }
+                                       hi=0;
+                                       lo=0;
+                                       found=0;
+                               }
+                       }
+               }
+               WDT_HIT();
+       }
+}
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