+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; // to be divided by 2
+ 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->threshold_sof + DecodeTag->previous_amplitude) { // 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:
+ // 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
+ 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)