+//-----------------------------------------------------------------------------
+// Read a TI-type tag. We assume that the tag has already been illuminated,
+// and that the exciting signal has been turned off. That means that we just
+// acquire the `one-bit DAC' bits from the comparator.
+//-----------------------------------------------------------------------------
+void AcquireTiType(void)
+{
+ int i;
+ int n = sizeof(BigBuf);
+
+ // clear buffer
+ memset(BigBuf,0,sizeof(BigBuf));
+
+ // Set up the synchronous serial port
+ PIO_DISABLE = (1<<GPIO_SSC_DIN);
+ PIO_PERIPHERAL_A_SEL = (1<<GPIO_SSC_DIN);
+
+ SSC_CONTROL = SSC_CONTROL_RESET;
+ SSC_CONTROL = SSC_CONTROL_RX_ENABLE | SSC_CONTROL_TX_ENABLE;
+
+ // 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
+ SSC_CLOCK_DIVISOR = 12;
+
+ SSC_RECEIVE_CLOCK_MODE = SSC_CLOCK_MODE_SELECT(0);
+ SSC_RECEIVE_FRAME_MODE = SSC_FRAME_MODE_BITS_IN_WORD(32) | SSC_FRAME_MODE_MSB_FIRST;
+ SSC_TRANSMIT_CLOCK_MODE = 0;
+ SSC_TRANSMIT_FRAME_MODE = 0;
+
+ i = 0;
+ for(;;) {
+ if(SSC_STATUS & SSC_STATUS_RX_READY) {
+ BigBuf[i] = SSC_RECEIVE_HOLDING; // store 32 bit values in buffer
+ i++; if(i >= n) return;
+ }
+ WDT_HIT();
+ }
+}
+
+void AcquireRawBitsTI(void)
+{
+ LED_D_ON();
+ // TI tags charge at 134.2Khz
+ FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
+
+ // Charge TI tag for 50ms.
+ SpinDelay(50);
+ LED_D_OFF();
+
+ LED_A_ON();
+ // Place FPGA in passthrough mode so as to stop driving the LF coil,
+ // in this mode the CROSS_LO line connects to SSP_DIN
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);
+
+ // get TI tag data into the buffer
+ AcquireTiType();
+
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+ LED_A_OFF();
+}
+