+ 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;