Add basic communication shell for Legic RF in reader mode. Needs the new receive function of hi_read_tx.

armsrc/appmain.c

@@ -553,6 +553,10 @@ void UsbPacketReceived(BYTE *packet, int len)
 			ReaderIso15693(c->ext1);
 			break;
 
+		case CMD_READER_LEGIC_RF:
+			LegicRfReader();
+			break;
+
 		case CMD_SIMTAG_ISO_15693:
 			SimTagIso15693(c->ext1);
 			break;

armsrc/legicrf.c

@@ -79,6 +79,108 @@ static void frame_send_tag(uint16_t response, int bits)
 #endif
 }
 
+/* Send a frame in reader mode, the FPGA must have been set up by
+ * LegicRfReader
+ */
+static void frame_send_rwd(uint16_t data, int bits)
+{
+	/* Start clock */
+	timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+	while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
+	
+	int i;
+	for(i=0; i<bits; i++) {
+		int starttime = timer->TC_CV;
+		int pause_end = starttime + RWD_TIME_PAUSE, bit_end;
+		int bit = data & 1;
+		data = data >> 1;
+		
+		if(bit) {
+			bit_end = starttime + RWD_TIME_1;
+		} else {
+			bit_end = starttime + RWD_TIME_0;
+		}
+		
+		/* RWD_TIME_PAUSE time off, then some time on, so that the complete bit time is
+		 * RWD_TIME_x, where x is the bit to be transmitted */
+		AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+		while(timer->TC_CV < pause_end) ;
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+		while(timer->TC_CV < bit_end) ;
+	}
+	
+	{
+		/* One final pause to mark the end of the frame */
+		int pause_end = timer->TC_CV + RWD_TIME_PAUSE;
+		AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+		while(timer->TC_CV < pause_end) ;
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+	}
+	
+	/* Reset the timer, to measure time until the start of the tag frame */
+	timer->TC_CCR = AT91C_TC_SWTRG;
+}
+
+/* Receive a frame from the card in reader emulation mode, the FPGA and
+ * timer must have been set up by LegicRfReader and frame_send_rwd.
+ * 
+ * The LEGIC RF protocol from card to reader does not include explicit
+ * frame start/stop information or length information. The reader must
+ * know beforehand how many bits it wants to receive. (Notably: a card
+ * sending a stream of 0-bits is indistinguishable from no card present.)
+ * 
+ * Receive methodology: There is a fancy correlator in hi_read_rx_xcorr, but
+ * I'm not smart enough to use it. Instead I have patched hi_read_tx to output
+ * the ADC signal with hysteresis on SSP_DIN. Bit-bang that signal and look
+ * for edges. Count the edges in each bit interval. If they are approximately
+ * 0 this was a 0-bit, if they are approximately equal to the number of edges
+ * expected for a 212kHz subcarrier, this was a 1-bit. For timing we use the
+ * timer that's still running from frame_send_rwd in order to get a synchronization
+ * with the frame that we just sent.
+ * 
+ * FIXME: Because we're relying on the hysteresis to just do the right thing 
+ * the range is severely reduced (and you'll probably also need a good antenna).
+ * So this should be fixed some time in the future for a proper receiver. 
+ */
+static void frame_receive_rwd(struct legic_frame * const f, int bits)
+{
+	uint16_t the_bit = 1;  /* Use a bitmask to save on shifts */
+	uint16_t data=0;
+	int i, old_level=0, edges=0;
+	int next_bit_at = TAG_TIME_WAIT;
+	
+	
+	if(bits > 16)
+		bits = 16;
+
+	AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
+	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
+
+	while(timer->TC_CV < next_bit_at) ;
+	next_bit_at += TAG_TIME_BIT;
+	
+	for(i=0; i<bits; i++) {
+		edges = 0;
+		while(timer->TC_CV < next_bit_at) {
+			int level = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
+			if(level != old_level)
+				edges++;
+			old_level = level;
+		}
+		next_bit_at += TAG_TIME_BIT;
+		
+		if(edges > 20 && edges < 60) { /* expected are 42 edges */
+			data |= the_bit;
+		}
+		
+		
+		the_bit <<= 1;
+	}
+	
+	f->data = data;
+	f->bits = bits;
+}
+
 /* Figure out a response to a frame in tag mode */
 static void frame_respond_tag(struct legic_frame const * const f)
 {
@@ -220,3 +322,39 @@ void LegicRfSimulate(void)
 		WDT_HIT();
 	}
 }
+
+void LegicRfReader(void)
+{
+	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+	FpgaSetupSsc();
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
+	
+	/* Bitbang the transmitter */
+	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
+	
+	setup_timer();
+	
+	while(!BUTTON_PRESS()) {
+		/* Switch on carrier and let the tag charge for 1ms */
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+		SpinDelay(1);
+		
+		LED_A_ON();
+		frame_send_rwd(queries[0].data, queries[0].bits);
+		LED_A_OFF();
+		
+		frame_clean(&current_frame);
+		LED_B_ON();
+		frame_receive_rwd(&current_frame, responses[0].bits);
+		LED_B_OFF();
+		
+		/* Switch off carrier, make sure tag is reset */
+		AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+		SpinDelay(10);
+		
+		WDT_HIT();
+	}
+	
+}

armsrc/legicrf.h

@@ -8,5 +8,6 @@
 #define LEGICRF_H_
 
 extern void LegicRfSimulate(void);
+extern void LegicRfReader(void);
 
 #endif /* LEGICRF_H_ */

include/usb_cmd.h

@@ -70,6 +70,7 @@ typedef struct {
 #define CMD_READER_ISO_14443a													0x0385
 #define CMD_SIMULATE_MIFARE_CARD											0x0386
 #define CMD_SIMULATE_TAG_LEGIC_RF					0x387
+#define CMD_READER_LEGIC_RF						0x388
 
 // For measurements of the antenna tuning
 #define CMD_MEASURE_ANTENNA_TUNING										0x0400

winsrc/command.cpp

@@ -214,6 +214,13 @@ static void CmdLegicRfSim(char *str)
 	SendCommand(&c, FALSE);
 }
 
+static void CmdLegicRfRead(char *str)
+{
+	UsbCommand c;
+	c.cmd = CMD_READER_LEGIC_RF;
+	SendCommand(&c, FALSE);
+}
+
 static void CmdFPGAOff(char *str)		// ## FPGA Control
 {
 	UsbCommand c;
@@ -2908,6 +2915,7 @@ static struct {
 	{"lcd",						CmdLcd,							0, "<HEX command> <count> -- Send command/data to LCD"},
 	{"lcdreset",			CmdLcdReset,				0, "Hardware reset LCD"},
 	{"legicrfsim",			CmdLegicRfSim,							0, "Start the LEGIC RF tag simulator"},
+	{"legicrfread",			CmdLegicRfRead,							0, "Start the LEGIC RF reader"},
 	{"load",					CmdLoad,						1, "<filename> -- Load trace (to graph window"},
 	{"locomread",			CmdLoCommandRead,		0, "<off period> <'0' period> <'1' period> <command> ['h'] -- Modulate LF reader field to send command before read (all periods in microseconds) (option 'h' for 134)"},
 	{"loread",				CmdLoread,					0, "['h'] -- Read 125/134 kHz LF ID-only tag (option 'h' for 134)"},