+
+ // EOF
+ ToSend[++ToSendMax] = 0x20; //0010 + 0000 padding
+
+ ToSendMax++;
+}
+
+// encode data using "1 out of 256" scheme
+// data rate is 1,66 kbit/s (fc/8192)
+// is designed for more robust communication over longer distances
+static void CodeIso15693AsReader256(uint8_t *cmd, int n)
+{
+ ToSendReset();
+
+ // SOF for 1of256
+ ToSend[++ToSendMax] = 0x81; //10000001
+
+ // data
+ for(int i = 0; i < n; i++) {
+ for (int j = 0; j <= 255; j++) {
+ if (cmd[i] == j) {
+ ToSendStuffBit(0);
+ ToSendStuffBit(1);
+ } else {
+ ToSendStuffBit(0);
+ ToSendStuffBit(0);
+ }
+ }
+ }
+
+ // EOF
+ ToSend[++ToSendMax] = 0x20; //0010 + 0000 padding
+
+ ToSendMax++;
+}
+
+
+// static uint8_t encode4Bits(const uint8_t b) {
+ // uint8_t c = b & 0xF;
+ // // OTA, the least significant bits first
+ // // The columns are
+ // // 1 - Bit value to send
+ // // 2 - Reversed (big-endian)
+ // // 3 - Manchester Encoded
+ // // 4 - Hex values
+
+ // switch(c){
+ // // 1 2 3 4
+ // case 15: return 0x55; // 1111 -> 1111 -> 01010101 -> 0x55
+ // case 14: return 0x95; // 1110 -> 0111 -> 10010101 -> 0x95
+ // case 13: return 0x65; // 1101 -> 1011 -> 01100101 -> 0x65
+ // case 12: return 0xa5; // 1100 -> 0011 -> 10100101 -> 0xa5
+ // case 11: return 0x59; // 1011 -> 1101 -> 01011001 -> 0x59
+ // case 10: return 0x99; // 1010 -> 0101 -> 10011001 -> 0x99
+ // case 9: return 0x69; // 1001 -> 1001 -> 01101001 -> 0x69
+ // case 8: return 0xa9; // 1000 -> 0001 -> 10101001 -> 0xa9
+ // case 7: return 0x56; // 0111 -> 1110 -> 01010110 -> 0x56
+ // case 6: return 0x96; // 0110 -> 0110 -> 10010110 -> 0x96
+ // case 5: return 0x66; // 0101 -> 1010 -> 01100110 -> 0x66
+ // case 4: return 0xa6; // 0100 -> 0010 -> 10100110 -> 0xa6
+ // case 3: return 0x5a; // 0011 -> 1100 -> 01011010 -> 0x5a
+ // case 2: return 0x9a; // 0010 -> 0100 -> 10011010 -> 0x9a
+ // case 1: return 0x6a; // 0001 -> 1000 -> 01101010 -> 0x6a
+ // default: return 0xaa; // 0000 -> 0000 -> 10101010 -> 0xaa
+
+ // }
+// }
+
+static const uint8_t encode_4bits[16] = { 0xaa, 0x6a, 0x9a, 0x5a, 0xa6, 0x66, 0x96, 0x56, 0xa9, 0x69, 0x99, 0x59, 0xa5, 0x65, 0x95, 0x55 };
+
+void CodeIso15693AsTag(uint8_t *cmd, size_t len) {
+ /*
+ * SOF comprises 3 parts;
+ * * An unmodulated time of 56.64 us
+ * * 24 pulses of 423.75 kHz (fc/32)
+ * * A logic 1, which starts with an unmodulated time of 18.88us
+ * followed by 8 pulses of 423.75kHz (fc/32)
+ *
+ * EOF comprises 3 parts:
+ * - A logic 0 (which starts with 8 pulses of fc/32 followed by an unmodulated
+ * time of 18.88us.
+ * - 24 pulses of fc/32
+ * - An unmodulated time of 56.64 us
+ *
+ * A logic 0 starts with 8 pulses of fc/32
+ * followed by an unmodulated time of 256/fc (~18,88us).
+ *
+ * A logic 0 starts with unmodulated time of 256/fc (~18,88us) followed by
+ * 8 pulses of fc/32 (also 18.88us)
+ *
+ * A bit here becomes 8 pulses of fc/32. Therefore:
+ * The SOF can be written as 00011101 = 0x1D
+ * The EOF can be written as 10111000 = 0xb8
+ * A logic 1 is 01
+ * A logic 0 is 10
+ *
+ * */
+
+ ToSendReset();
+
+ // SOF
+ ToSend[++ToSendMax] = 0x1D; // 00011101
+
+ // data
+ for (int i = 0; i < len; i++) {
+ ToSend[++ToSendMax] = encode_4bits[cmd[i] & 0xF];
+ ToSend[++ToSendMax] = encode_4bits[cmd[i] >> 4];
+ }
+
+ // EOF
+ ToSend[++ToSendMax] = 0xB8; // 10111000
+
+ ToSendMax++;
+}
+
+
+// Transmit the command (to the tag) that was placed in cmd[].
+void TransmitTo15693Tag(const uint8_t *cmd, int len, uint32_t *start_time) {
+
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_MODE_SEND_FULL_MOD);
+
+ if (*start_time < DELAY_ARM_TO_TAG) {
+ *start_time = DELAY_ARM_TO_TAG;
+ }
+
+ *start_time = (*start_time - DELAY_ARM_TO_TAG) & 0xfffffff0;
+
+ while (GetCountSspClk() > *start_time) { // we may miss the intended time
+ *start_time += 16; // next possible time
+ }
+
+
+ while (GetCountSspClk() < *start_time)
+ /* wait */ ;
+
+ LED_B_ON();
+ for (int c = 0; c < len; c++) {
+ uint8_t data = cmd[c];
+ for (int i = 0; i < 8; i++) {
+ uint16_t send_word = (data & 0x80) ? 0xffff : 0x0000;
+ while (!(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY))) ;
+ AT91C_BASE_SSC->SSC_THR = send_word;
+ while (!(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY))) ;
+ AT91C_BASE_SSC->SSC_THR = send_word;
+
+ data <<= 1;
+ }
+ WDT_HIT();
+ }
+ LED_B_OFF();
+
+ *start_time = *start_time + DELAY_ARM_TO_TAG;
+
+}
+
+
+//-----------------------------------------------------------------------------
+// Transmit the tag response (to the reader) that was placed in cmd[].
+//-----------------------------------------------------------------------------
+void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t *start_time, uint32_t slot_time, bool slow) {
+ // don't use the FPGA_HF_SIMULATOR_MODULATE_424K_8BIT minor mode. It would spoil GetCountSspClk()
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_424K);
+
+ uint32_t modulation_start_time = *start_time - DELAY_ARM_TO_READER + 3 * 8; // no need to transfer the unmodulated start of SOF
+
+ while (GetCountSspClk() > (modulation_start_time & 0xfffffff8) + 3) { // we will miss the intended time
+ if (slot_time) {
+ modulation_start_time += slot_time; // use next available slot
+ } else {
+ modulation_start_time = (modulation_start_time & 0xfffffff8) + 8; // next possible time
+ }
+ }
+
+ while (GetCountSspClk() < (modulation_start_time & 0xfffffff8))
+ /* wait */ ;
+
+ uint8_t shift_delay = modulation_start_time & 0x00000007;
+
+ *start_time = modulation_start_time + DELAY_ARM_TO_READER - 3 * 8;
+
+ LED_C_ON();
+ uint8_t bits_to_shift = 0x00;
+ uint8_t bits_to_send = 0x00;
+ for (size_t c = 0; c < len; c++) {
+ for (int i = (c==0?4:7); i >= 0; i--) {
+ uint8_t cmd_bits = ((cmd[c] >> i) & 0x01) ? 0xff : 0x00;
+ for (int j = 0; j < (slow?4:1); ) {
+ if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
+ bits_to_send = bits_to_shift << (8 - shift_delay) | cmd_bits >> shift_delay;
+ AT91C_BASE_SSC->SSC_THR = bits_to_send;
+ bits_to_shift = cmd_bits;
+ j++;
+ }
+ }
+ }
+ WDT_HIT();
+ }
+ // send the remaining bits, padded with 0:
+ bits_to_send = bits_to_shift << (8 - shift_delay);
+ for ( ; ; ) {
+ if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
+ AT91C_BASE_SSC->SSC_THR = bits_to_send;
+ break;
+ }
+ }
+ LED_C_OFF();
+}
+
+
+//=============================================================================
+// An ISO 15693 decoder for tag responses (one subcarrier only).
+// Uses cross correlation to identify each bit and EOF.
+// This function is called 8 times per bit (every 2 subcarrier cycles).
+// Subcarrier frequency fs is 424kHz, 1/fs = 2,36us,
+// i.e. function is called every 4,72us
+// LED handling:
+// LED C -> ON once we have received the SOF and are expecting the rest.
+// LED C -> OFF once we have received EOF or are unsynced
+//
+// Returns: true if we received a EOF
+// false if we are still waiting for some more
+//=============================================================================
+
+#define NOISE_THRESHOLD 160 // don't try to correlate noise
+#define MAX_PREVIOUS_AMPLITUDE (-1 - NOISE_THRESHOLD)
+
+typedef struct DecodeTag {
+ enum {
+ STATE_TAG_SOF_LOW,
+ STATE_TAG_SOF_RISING_EDGE,
+ STATE_TAG_SOF_HIGH,
+ STATE_TAG_SOF_HIGH_END,
+ STATE_TAG_RECEIVING_DATA,
+ STATE_TAG_EOF,
+ STATE_TAG_EOF_TAIL
+ } state;
+ int bitCount;
+ int posCount;
+ enum {
+ LOGIC0,
+ LOGIC1,
+ SOF_PART1,
+ SOF_PART2
+ } lastBit;
+ uint16_t shiftReg;
+ uint16_t max_len;
+ uint8_t *output;
+ int len;
+ int sum1, sum2;
+ int threshold_sof;
+ int threshold_half;
+ uint16_t previous_amplitude;
+} DecodeTag_t;
+
+
+static int inline __attribute__((always_inline)) Handle15693SamplesFromTag(uint16_t amplitude, DecodeTag_t *DecodeTag)
+{
+ switch(DecodeTag->state) {
+ case STATE_TAG_SOF_LOW:
+ // waiting for a rising edge
+ if (amplitude > NOISE_THRESHOLD + DecodeTag->previous_amplitude) {
+ if (DecodeTag->posCount > 10) {
+ DecodeTag->threshold_sof = amplitude - DecodeTag->previous_amplitude;
+ DecodeTag->threshold_half = 0;
+ DecodeTag->state = STATE_TAG_SOF_RISING_EDGE;
+ } else {
+ DecodeTag->posCount = 0;
+ }
+ } else {
+ DecodeTag->posCount++;
+ DecodeTag->previous_amplitude = amplitude;
+ }
+ break;
+
+ case STATE_TAG_SOF_RISING_EDGE:
+ if (amplitude - DecodeTag->previous_amplitude > DecodeTag->threshold_sof) { // edge still rising
+ if (amplitude - DecodeTag->threshold_sof > DecodeTag->threshold_sof) { // steeper edge, take this as time reference
+ DecodeTag->posCount = 1;
+ } else {
+ DecodeTag->posCount = 2;
+ }
+ DecodeTag->threshold_sof = (amplitude - DecodeTag->previous_amplitude) / 2;
+ } else {
+ DecodeTag->posCount = 2;
+ DecodeTag->threshold_sof = DecodeTag->threshold_sof/2;
+ }
+ // DecodeTag->posCount = 2;
+ DecodeTag->state = STATE_TAG_SOF_HIGH;
+ break;
+
+ case STATE_TAG_SOF_HIGH:
+ // waiting for 10 times high. Take average over the last 8
+ if (amplitude > DecodeTag->threshold_sof) {
+ DecodeTag->posCount++;
+ if (DecodeTag->posCount > 2) {
+ DecodeTag->threshold_half += amplitude; // keep track of average high value
+ }
+ if (DecodeTag->posCount == 10) {
+ DecodeTag->threshold_half >>= 2; // (4 times 1/2 average)
+ DecodeTag->state = STATE_TAG_SOF_HIGH_END;
+ }
+ } else { // high phase was too short
+ DecodeTag->posCount = 1;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ }
+ break;
+
+ case STATE_TAG_SOF_HIGH_END:
+ // check for falling edge
+ if (DecodeTag->posCount == 13 && amplitude < DecodeTag->threshold_sof) {
+ DecodeTag->lastBit = SOF_PART1; // detected 1st part of SOF (12 samples low and 12 samples high)
+ DecodeTag->shiftReg = 0;
+ DecodeTag->bitCount = 0;
+ DecodeTag->len = 0;
+ DecodeTag->sum1 = amplitude;
+ DecodeTag->sum2 = 0;
+ DecodeTag->posCount = 2;
+ DecodeTag->state = STATE_TAG_RECEIVING_DATA;
+ FpgaDisableTracing(); // DEBUGGING
+ Dbprintf("amplitude = %d, threshold_sof = %d, threshold_half/4 = %d, previous_amplitude = %d",
+ amplitude,
+ DecodeTag->threshold_sof,
+ DecodeTag->threshold_half/4,
+ DecodeTag->previous_amplitude); // DEBUGGING
+ LED_C_ON();
+ } else {
+ DecodeTag->posCount++;
+ if (DecodeTag->posCount > 13) { // high phase too long
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ }
+ break;
+
+ case STATE_TAG_RECEIVING_DATA:
+ if (DecodeTag->posCount == 1) {
+ DecodeTag->sum1 = 0;
+ DecodeTag->sum2 = 0;
+ }
+ if (DecodeTag->posCount <= 4) {
+ DecodeTag->sum1 += amplitude;
+ } else {
+ DecodeTag->sum2 += amplitude;
+ }
+ if (DecodeTag->posCount == 8) {
+ if (DecodeTag->sum1 > DecodeTag->threshold_half && DecodeTag->sum2 > DecodeTag->threshold_half) { // modulation in both halves
+ if (DecodeTag->lastBit == LOGIC0) { // this was already part of EOF
+ DecodeTag->state = STATE_TAG_EOF;
+ } else {
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ } else if (DecodeTag->sum1 < DecodeTag->threshold_half && DecodeTag->sum2 > DecodeTag->threshold_half) { // modulation in second half
+ // logic 1
+ if (DecodeTag->lastBit == SOF_PART1) { // still part of SOF
+ DecodeTag->lastBit = SOF_PART2; // SOF completed
+ } else {
+ DecodeTag->lastBit = LOGIC1;
+ DecodeTag->shiftReg >>= 1;
+ DecodeTag->shiftReg |= 0x80;
+ DecodeTag->bitCount++;
+ if (DecodeTag->bitCount == 8) {
+ DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+ DecodeTag->len++;
+ // if (DecodeTag->shiftReg == 0x12 && DecodeTag->len == 1) FpgaDisableTracing(); // DEBUGGING
+ if (DecodeTag->len > DecodeTag->max_len) {
+ // buffer overflow, give up
+ LED_C_OFF();
+ return true;
+ }
+ DecodeTag->bitCount = 0;
+ DecodeTag->shiftReg = 0;
+ }
+ }
+ } else if (DecodeTag->sum1 > DecodeTag->threshold_half && DecodeTag->sum2 < DecodeTag->threshold_half) { // modulation in first half
+ // logic 0
+ if (DecodeTag->lastBit == SOF_PART1) { // incomplete SOF
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ } else {
+ DecodeTag->lastBit = LOGIC0;
+ DecodeTag->shiftReg >>= 1;
+ DecodeTag->bitCount++;
+ if (DecodeTag->bitCount == 8) {
+ DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+ DecodeTag->len++;
+ // if (DecodeTag->shiftReg == 0x12 && DecodeTag->len == 1) FpgaDisableTracing(); // DEBUGGING
+ if (DecodeTag->len > DecodeTag->max_len) {
+ // buffer overflow, give up
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ DecodeTag->bitCount = 0;
+ DecodeTag->shiftReg = 0;
+ }
+ }
+ } else { // no modulation
+ if (DecodeTag->lastBit == SOF_PART2) { // only SOF (this is OK for iClass)
+ LED_C_OFF();
+ return true;
+ } else {
+ DecodeTag->posCount = 0;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ }
+ DecodeTag->posCount = 0;
+ }
+ DecodeTag->posCount++;
+ break;
+
+ case STATE_TAG_EOF:
+ if (DecodeTag->posCount == 1) {
+ DecodeTag->sum1 = 0;
+ DecodeTag->sum2 = 0;
+ }
+ if (DecodeTag->posCount <= 4) {
+ DecodeTag->sum1 += amplitude;
+ } else {
+ DecodeTag->sum2 += amplitude;
+ }
+ if (DecodeTag->posCount == 8) {
+ if (DecodeTag->sum1 > DecodeTag->threshold_half && DecodeTag->sum2 < DecodeTag->threshold_half) { // modulation in first half
+ DecodeTag->posCount = 0;
+ DecodeTag->state = STATE_TAG_EOF_TAIL;
+ } else {
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ }
+ DecodeTag->posCount++;
+ break;
+
+ case STATE_TAG_EOF_TAIL:
+ if (DecodeTag->posCount == 1) {
+ DecodeTag->sum1 = 0;
+ DecodeTag->sum2 = 0;
+ }
+ if (DecodeTag->posCount <= 4) {
+ DecodeTag->sum1 += amplitude;
+ } else {
+ DecodeTag->sum2 += amplitude;
+ }
+ if (DecodeTag->posCount == 8) {
+ if (DecodeTag->sum1 < DecodeTag->threshold_half && DecodeTag->sum2 < DecodeTag->threshold_half) { // no modulation in both halves
+ LED_C_OFF();
+ return true;
+ } else {
+ DecodeTag->posCount = 0;
+ DecodeTag->previous_amplitude = amplitude;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ LED_C_OFF();
+ }
+ }
+ DecodeTag->posCount++;
+ break;
+ }
+
+ return false;
+}
+
+
+static void DecodeTagInit(DecodeTag_t *DecodeTag, uint8_t *data, uint16_t max_len) {
+ DecodeTag->previous_amplitude = MAX_PREVIOUS_AMPLITUDE;
+ DecodeTag->posCount = 0;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ DecodeTag->output = data;
+ DecodeTag->max_len = max_len;
+}
+
+
+static void DecodeTagReset(DecodeTag_t *DecodeTag) {
+ DecodeTag->posCount = 0;
+ DecodeTag->state = STATE_TAG_SOF_LOW;
+ DecodeTag->previous_amplitude = MAX_PREVIOUS_AMPLITUDE;
+}
+
+
+/*
+ * Receive and decode the tag response, also log to tracebuffer
+ */
+int GetIso15693AnswerFromTag(uint8_t* response, uint16_t max_len, uint16_t timeout, uint32_t *eof_time) {
+
+ int samples = 0;
+ int ret = 0;
+
+ uint16_t dmaBuf[ISO15693_DMA_BUFFER_SIZE];
+
+ // the Decoder data structure
+ DecodeTag_t DecodeTag = { 0 };
+ DecodeTagInit(&DecodeTag, response, max_len);
+
+ // wait for last transfer to complete
+ while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
+
+ // And put the FPGA in the appropriate mode
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_424_KHZ | FPGA_HF_READER_MODE_RECEIVE_AMPLITUDE);
+
+ // Setup and start DMA.
+ FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+ FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+ uint32_t dma_start_time = 0;
+ uint16_t *upTo = dmaBuf;
+
+ for(;;) {
+ uint16_t behindBy = ((uint16_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (ISO15693_DMA_BUFFER_SIZE-1);
+
+ if (behindBy == 0) continue;
+
+ samples++;
+ if (samples == 1) {
+ // DMA has transferred the very first data
+ dma_start_time = GetCountSspClk() & 0xfffffff0;
+ }
+
+ uint16_t tagdata = *upTo++;
+
+ if(upTo >= dmaBuf + ISO15693_DMA_BUFFER_SIZE) { // we have read all of the DMA buffer content.
+ upTo = dmaBuf; // start reading the circular buffer from the beginning
+ if(behindBy > (9*ISO15693_DMA_BUFFER_SIZE/10)) {
+ Dbprintf("About to blow circular buffer - aborted! behindBy=%d", behindBy);
+ ret = -1;
+ break;
+ }
+ }
+ if (AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_ENDRX)) { // DMA Counter Register had reached 0, already rotated.
+ AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf; // refresh the DMA Next Buffer and
+ AT91C_BASE_PDC_SSC->PDC_RNCR = ISO15693_DMA_BUFFER_SIZE; // DMA Next Counter registers
+ }
+
+ if (Handle15693SamplesFromTag(tagdata, &DecodeTag)) {
+ *eof_time = dma_start_time + samples*16 - DELAY_TAG_TO_ARM; // end of EOF
+ if (DecodeTag.lastBit == SOF_PART2) {
+ *eof_time -= 8*16; // needed 8 additional samples to confirm single SOF (iCLASS)
+ }
+ if (DecodeTag.len > DecodeTag.max_len) {
+ ret = -2; // buffer overflow
+ }
+ break;
+ }
+
+ if (samples > timeout && DecodeTag.state < STATE_TAG_RECEIVING_DATA) {
+ ret = -1; // timeout
+ break;
+ }
+
+ }
+
+ FpgaDisableSscDma();
+
+ if (DEBUG) Dbprintf("samples = %d, ret = %d, Decoder: state = %d, lastBit = %d, len = %d, bitCount = %d, posCount = %d",
+ samples, ret, DecodeTag.state, DecodeTag.lastBit, DecodeTag.len, DecodeTag.bitCount, DecodeTag.posCount);
+
+ if (ret < 0) {
+ return ret;
+ }
+
+ uint32_t sof_time = *eof_time
+ - DecodeTag.len * 8 * 8 * 16 // time for byte transfers
+ - 32 * 16 // time for SOF transfer
+ - (DecodeTag.lastBit != SOF_PART2?32*16:0); // time for EOF transfer
+
+ if (DEBUG) Dbprintf("timing: sof_time = %d, eof_time = %d", sof_time, *eof_time);
+
+ LogTrace_ISO15693(DecodeTag.output, DecodeTag.len, sof_time*4, *eof_time*4, NULL, false);
+
+ return DecodeTag.len;
+}
+
+
+//=============================================================================
+// An ISO15693 decoder for reader commands.
+//
+// This function is called 4 times per bit (every 2 subcarrier cycles).
+// Subcarrier frequency fs is 848kHz, 1/fs = 1,18us, i.e. function is called every 2,36us
+// LED handling:
+// LED B -> ON once we have received the SOF and are expecting the rest.
+// LED B -> OFF once we have received EOF or are in error state or unsynced
+//
+// Returns: true if we received a EOF
+// false if we are still waiting for some more
+//=============================================================================
+
+typedef struct DecodeReader {
+ enum {
+ STATE_READER_UNSYNCD,
+ STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF,
+ STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF,
+ STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF,
+ STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF,
+ STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4,
+ STATE_READER_RECEIVE_DATA_1_OUT_OF_4,
+ STATE_READER_RECEIVE_DATA_1_OUT_OF_256
+ } state;
+ enum {
+ CODING_1_OUT_OF_4,
+ CODING_1_OUT_OF_256
+ } Coding;
+ uint8_t shiftReg;
+ uint8_t bitCount;
+ int byteCount;
+ int byteCountMax;
+ int posCount;
+ int sum1, sum2;
+ uint8_t *output;
+} DecodeReader_t;
+
+
+static void DecodeReaderInit(DecodeReader_t* DecodeReader, uint8_t *data, uint16_t max_len)
+{
+ DecodeReader->output = data;
+ DecodeReader->byteCountMax = max_len;
+ DecodeReader->state = STATE_READER_UNSYNCD;
+ DecodeReader->byteCount = 0;
+ DecodeReader->bitCount = 0;
+ DecodeReader->posCount = 1;
+ DecodeReader->shiftReg = 0;
+}
+
+
+static void DecodeReaderReset(DecodeReader_t* DecodeReader)
+{
+ DecodeReader->state = STATE_READER_UNSYNCD;
+}
+
+
+static int inline __attribute__((always_inline)) Handle15693SampleFromReader(uint8_t bit, DecodeReader_t *restrict DecodeReader)
+{
+ switch (DecodeReader->state) {
+ case STATE_READER_UNSYNCD:
+ // wait for unmodulated carrier
+ if (bit) {
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ }
+ break;
+
+ case STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF:
+ if (!bit) {
+ // we went low, so this could be the beginning of a SOF
+ DecodeReader->posCount = 1;
+ DecodeReader->state = STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF;
+ }
+ break;
+
+ case STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF:
+ DecodeReader->posCount++;
+ if (bit) { // detected rising edge
+ if (DecodeReader->posCount < 4) { // rising edge too early (nominally expected at 5)
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ } else { // SOF
+ DecodeReader->state = STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF;
+ }
+ } else {
+ if (DecodeReader->posCount > 5) { // stayed low for too long
+ DecodeReaderReset(DecodeReader);
+ } else {
+ // do nothing, keep waiting
+ }
+ }
+ break;
+
+ case STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF:
+ DecodeReader->posCount++;
+ if (!bit) { // detected a falling edge
+ if (DecodeReader->posCount < 20) { // falling edge too early (nominally expected at 21 earliest)
+ DecodeReaderReset(DecodeReader);
+ } else if (DecodeReader->posCount < 23) { // SOF for 1 out of 4 coding
+ DecodeReader->Coding = CODING_1_OUT_OF_4;
+ DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
+ } else if (DecodeReader->posCount < 28) { // falling edge too early (nominally expected at 29 latest)
+ DecodeReaderReset(DecodeReader);
+ } else { // SOF for 1 out of 256 coding
+ DecodeReader->Coding = CODING_1_OUT_OF_256;
+ DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
+ }
+ } else {
+ if (DecodeReader->posCount > 29) { // stayed high for too long
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ } else {
+ // do nothing, keep waiting
+ }
+ }
+ break;
+
+ case STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF:
+ DecodeReader->posCount++;
+ if (bit) { // detected rising edge
+ if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
+ if (DecodeReader->posCount < 32) { // rising edge too early (nominally expected at 33)
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ } else {
+ DecodeReader->posCount = 1;
+ DecodeReader->bitCount = 0;
+ DecodeReader->byteCount = 0;
+ DecodeReader->sum1 = 1;
+ DecodeReader->state = STATE_READER_RECEIVE_DATA_1_OUT_OF_256;
+ LED_B_ON();
+ }
+ } else { // CODING_1_OUT_OF_4
+ if (DecodeReader->posCount < 24) { // rising edge too early (nominally expected at 25)
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ } else {
+ DecodeReader->posCount = 1;
+ DecodeReader->state = STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4;
+ }
+ }
+ } else {
+ if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
+ if (DecodeReader->posCount > 34) { // signal stayed low for too long
+ DecodeReaderReset(DecodeReader);
+ } else {
+ // do nothing, keep waiting
+ }
+ } else { // CODING_1_OUT_OF_4
+ if (DecodeReader->posCount > 26) { // signal stayed low for too long
+ DecodeReaderReset(DecodeReader);
+ } else {
+ // do nothing, keep waiting
+ }
+ }
+ }
+ break;
+
+ case STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4:
+ DecodeReader->posCount++;
+ if (bit) {
+ if (DecodeReader->posCount == 9) {
+ DecodeReader->posCount = 1;
+ DecodeReader->bitCount = 0;
+ DecodeReader->byteCount = 0;
+ DecodeReader->sum1 = 1;
+ DecodeReader->state = STATE_READER_RECEIVE_DATA_1_OUT_OF_4;
+ LED_B_ON();
+ } else {
+ // do nothing, keep waiting
+ }
+ } else { // unexpected falling edge
+ DecodeReaderReset(DecodeReader);
+ }
+ break;
+
+ case STATE_READER_RECEIVE_DATA_1_OUT_OF_4:
+ bit = !!bit;
+ DecodeReader->posCount++;
+ if (DecodeReader->posCount == 1) {
+ DecodeReader->sum1 = bit;
+ } else if (DecodeReader->posCount <= 4) {
+ DecodeReader->sum1 += bit;
+ } else if (DecodeReader->posCount == 5) {
+ DecodeReader->sum2 = bit;
+ } else {
+ DecodeReader->sum2 += bit;
+ }
+ if (DecodeReader->posCount == 8) {
+ DecodeReader->posCount = 0;
+ if (DecodeReader->sum1 <= 1 && DecodeReader->sum2 >= 3) { // EOF
+ LED_B_OFF(); // Finished receiving
+ DecodeReaderReset(DecodeReader);
+ if (DecodeReader->byteCount != 0) {
+ return true;
+ }
+ }
+ if (DecodeReader->sum1 >= 3 && DecodeReader->sum2 <= 1) { // detected a 2bit position
+ DecodeReader->shiftReg >>= 2;
+ DecodeReader->shiftReg |= (DecodeReader->bitCount << 6);
+ }
+ if (DecodeReader->bitCount == 15) { // we have a full byte
+ DecodeReader->output[DecodeReader->byteCount++] = DecodeReader->shiftReg;
+ if (DecodeReader->byteCount > DecodeReader->byteCountMax) {
+ // buffer overflow, give up
+ LED_B_OFF();
+ DecodeReaderReset(DecodeReader);
+ }
+ DecodeReader->bitCount = 0;
+ DecodeReader->shiftReg = 0;
+ } else {
+ DecodeReader->bitCount++;
+ }
+ }
+ break;
+
+ case STATE_READER_RECEIVE_DATA_1_OUT_OF_256:
+ bit = !!bit;
+ DecodeReader->posCount++;
+ if (DecodeReader->posCount == 1) {
+ DecodeReader->sum1 = bit;
+ } else if (DecodeReader->posCount <= 4) {
+ DecodeReader->sum1 += bit;
+ } else if (DecodeReader->posCount == 5) {
+ DecodeReader->sum2 = bit;
+ } else {
+ DecodeReader->sum2 += bit;
+ }
+ if (DecodeReader->posCount == 8) {
+ DecodeReader->posCount = 0;
+ if (DecodeReader->sum1 <= 1 && DecodeReader->sum2 >= 3) { // EOF
+ LED_B_OFF(); // Finished receiving
+ DecodeReaderReset(DecodeReader);
+ if (DecodeReader->byteCount != 0) {
+ return true;
+ }
+ }
+ if (DecodeReader->sum1 >= 3 && DecodeReader->sum2 <= 1) { // detected the bit position
+ DecodeReader->shiftReg = DecodeReader->bitCount;
+ }
+ if (DecodeReader->bitCount == 255) { // we have a full byte
+ DecodeReader->output[DecodeReader->byteCount++] = DecodeReader->shiftReg;
+ if (DecodeReader->byteCount > DecodeReader->byteCountMax) {
+ // buffer overflow, give up
+ LED_B_OFF();
+ DecodeReaderReset(DecodeReader);
+ }
+ }
+ DecodeReader->bitCount++;
+ }
+ break;
+
+ default:
+ LED_B_OFF();
+ DecodeReaderReset(DecodeReader);
+ break;
+ }
+
+ return false;
+}
+
+
+//-----------------------------------------------------------------------------
+// Receive a command (from the reader to us, where we are the simulated tag),
+// and store it in the given buffer, up to the given maximum length. Keeps
+// spinning, waiting for a well-framed command, until either we get one
+// (returns len) or someone presses the pushbutton on the board (returns -1).
+//
+// Assume that we're called with the SSC (to the FPGA) and ADC path set
+// correctly.
+//-----------------------------------------------------------------------------
+
+int GetIso15693CommandFromReader(uint8_t *received, size_t max_len, uint32_t *eof_time) {
+ int samples = 0;
+ bool gotFrame = false;
+ uint8_t b;
+
+ uint8_t dmaBuf[ISO15693_DMA_BUFFER_SIZE];
+
+ // the decoder data structure
+ DecodeReader_t DecodeReader = {0};
+ DecodeReaderInit(&DecodeReader, received, max_len);
+
+ // wait for last transfer to complete
+ while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
+
+ LED_D_OFF();
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
+
+ // clear receive register and wait for next transfer
+ uint32_t temp = AT91C_BASE_SSC->SSC_RHR;
+ (void) temp;
+ while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY)) ;
+
+ uint32_t dma_start_time = GetCountSspClk() & 0xfffffff8;
+
+ // Setup and start DMA.
+ FpgaSetupSscDma(dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+ uint8_t *upTo = dmaBuf;
+
+ for (;;) {
+ uint16_t behindBy = ((uint8_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (ISO15693_DMA_BUFFER_SIZE-1);
+
+ if (behindBy == 0) continue;
+
+ b = *upTo++;
+ if (upTo >= dmaBuf + ISO15693_DMA_BUFFER_SIZE) { // we have read all of the DMA buffer content.
+ upTo = dmaBuf; // start reading the circular buffer from the beginning
+ if (behindBy > (9*ISO15693_DMA_BUFFER_SIZE/10)) {
+ Dbprintf("About to blow circular buffer - aborted! behindBy=%d", behindBy);
+ break;
+ }
+ }
+ if (AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_ENDRX)) { // DMA Counter Register had reached 0, already rotated.
+ AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf; // refresh the DMA Next Buffer and
+ AT91C_BASE_PDC_SSC->PDC_RNCR = ISO15693_DMA_BUFFER_SIZE; // DMA Next Counter registers
+ }
+
+ for (int i = 7; i >= 0; i--) {
+ if (Handle15693SampleFromReader((b >> i) & 0x01, &DecodeReader)) {
+ *eof_time = dma_start_time + samples - DELAY_READER_TO_ARM; // end of EOF
+ gotFrame = true;
+ break;
+ }
+ samples++;
+ }
+
+ if (gotFrame) {
+ break;
+ }
+
+ if (BUTTON_PRESS()) {
+ DecodeReader.byteCount = -1;
+ break;
+ }
+
+ WDT_HIT();
+ }
+
+ FpgaDisableSscDma();
+
+ if (DEBUG) Dbprintf("samples = %d, gotFrame = %d, Decoder: state = %d, len = %d, bitCount = %d, posCount = %d",
+ samples, gotFrame, DecodeReader.state, DecodeReader.byteCount, DecodeReader.bitCount, DecodeReader.posCount);
+
+ if (DecodeReader.byteCount > 0) {
+ uint32_t sof_time = *eof_time
+ - DecodeReader.byteCount * (DecodeReader.Coding==CODING_1_OUT_OF_4?128:2048) // time for byte transfers
+ - 32 // time for SOF transfer
+ - 16; // time for EOF transfer
+ LogTrace_ISO15693(DecodeReader.output, DecodeReader.byteCount, sof_time*32, *eof_time*32, NULL, true);
projects / proxmark3-svn / blobdiff