X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/ccedd6ae6b6cde1899635ca9767ccc124db0156a..1d99b0df4a0c1a2f42fe23ae32cc8f3d090bc985:/armsrc/legicrf.c

diff --git a/armsrc/legicrf.c b/armsrc/legicrf.c
index 6a40b037..7c3460af 100644
--- a/armsrc/legicrf.c
+++ b/armsrc/legicrf.c
@@ -15,88 +15,131 @@ static struct legic_frame {
 	int bits;
 	uint16_t data;
 } current_frame;
+AT91PS_TC timer;
 
-static struct legic_frame queries[] = {
-		{7, 0x55}, /* 1010 101 */
-};
+static void setup_timer(void)
+{
+	/* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
+	 * this it won't be terribly accurate but should be good enough.
+	 */
+	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
+	timer = AT91C_BASE_TC1;
+	timer->TC_CCR = AT91C_TC_CLKDIS;
+	timer->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
+	timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
 
-static struct legic_frame responses[] = {
-		{6, 0x3b}, /* 1101 11 */
-};
+/* At TIMER_CLOCK3 (MCK/32) */
+#define	RWD_TIME_1 150     /* RWD_TIME_PAUSE off, 80us on = 100us */
+#define RWD_TIME_0 90      /* RWD_TIME_PAUSE off, 40us on = 60us */
+#define RWD_TIME_PAUSE 30  /* 20us */
+#define RWD_TIME_FUZZ 20   /* rather generous 13us, since the peak detector + hysteresis fuzz quite a bit */
+#define TAG_TIME_BIT 150   /* 100us for every bit */
+#define TAG_TIME_WAIT 490  /* time from RWD frame end to tag frame start, experimentally determined */
 
-static void frame_send(uint16_t response, int bits)
-{
-#if 0
-	/* Use the SSC to send a response. 8-bit transfers, LSBit first, 100us per bit */
-#else 
-	/* Bitbang the response */
-	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
-	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
-	
-	/* Wait for the frame start */
-	while(AT91C_BASE_TC1->TC_CV < 490) ;
-	
-	int i;
-	for(i=0; i<bits; i++) {
-		int nextbit = AT91C_BASE_TC1->TC_CV + 150;
-		int bit = response & 1;
-		response = response >> 1;
-		if(bit) 
-			AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
-		else
-			AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-		while(AT91C_BASE_TC1->TC_CV < nextbit) ;
-	}
-	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-#endif
 }
 
-static void frame_respond(struct legic_frame const * const f)
+#define FUZZ_EQUAL(value, target, fuzz) ((value) > ((target)-(fuzz)) && (value) < ((target)+(fuzz)))
+
+/* 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)
 {
-	LED_D_ON();
-	int i;
-	struct legic_frame *r = NULL;
+	/* Start clock */
+	timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+	while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
 	
-	for(i=0; i<sizeof(queries)/sizeof(queries[0]); i++) {
-		if(f->bits == queries[i].bits && f->data == queries[i].data) {
-			r = &responses[i];
-			break;
+	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) ;
 	}
 	
-	if(r != NULL) {
-		frame_send(r->data, r->bits);
-		LED_A_ON();
-	} else {
-		LED_A_OFF();
+	{
+		/* 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;
 	}
 	
-	LED_D_OFF();
+	/* Reset the timer, to measure time until the start of the tag frame */
+	timer->TC_CCR = AT91C_TC_SWTRG;
 }
 
-static void frame_append_bit(struct legic_frame * const f, int bit)
+/* 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)
 {
-	if(f->bits >= 15)
-		return; /* Overflow, won't happen */
-	f->data |= (bit<<f->bits);
-	f->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;
 
-static int frame_is_empty(struct legic_frame const * const f)
-{
-	return( f->bits <= 4 );
-}
+	AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
+	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
 
-static void frame_handle(struct legic_frame const * const f)
-{
-	if(f->bits == 6) {
-		/* Short path */
-		return;
-	}
-	if( !frame_is_empty(f) ) {
-		frame_respond(f);
+	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;
 }
 
 static void frame_clean(struct legic_frame * const f)
@@ -105,92 +148,38 @@ static void frame_clean(struct legic_frame * const f)
 	f->bits = 0;
 }
 
-static void emit(int bit)
+void LegicRfReader(void)
 {
-	if(bit == -1) {
-		frame_handle(&current_frame);
-		frame_clean(&current_frame);
-	} else if(bit == 0) {
-		frame_append_bit(&current_frame, 0);
-	} else if(bit == 1) {
-		frame_append_bit(&current_frame, 1);
-	}
-}
-
-void LegicRfSimulate(void)
-{
-	/* ADC path high-frequency peak detector, FPGA in high-frequency simulator mode, 
-	 * modulation mode set to 212kHz subcarrier. We are getting the incoming raw
-	 * envelope waveform on DIN and should send our response on DOUT.
-	 * 
-	 * The LEGIC RF protocol is pulse-pause-encoding from reader to card, so we'll
-	 * measure the time between two rising edges on DIN, and no encoding on the
-	 * subcarrier from card to reader, so we'll just shift out our verbatim data
-	 * on DOUT, 1 bit is 100us. The time from reader to card frame is still unclear,
-	 * seems to be 300us-ish.
-	 */
 	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 	FpgaSetupSsc();
-	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_212K);
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
 	
-	/* Bitbang the receiver */
-	AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
-	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
+	/* 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;
 	
-	/* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
-	 * this it won't be terribly accurate but should be good enough.
-	 */
-	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
-	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
-	AT91C_BASE_TC1->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
-	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-	int old_level = 0;
-
-/* At TIMER_CLOCK3 (MCK/32) */
-#define	BIT_TIME_1 150
-#define BIT_TIME_0 90
-#define BIT_TIME_FUZZ 20
+	setup_timer();
 	
-	int active = 0;
 	while(!BUTTON_PRESS()) {
-		int level = !!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
-		int time = AT91C_BASE_TC1->TC_CV;
+		/* Switch on carrier and let the tag charge for 1ms */
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+		SpinDelay(1);
 		
-		if(level != old_level) {
-			if(level == 1) {
-				AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-				if(time > (BIT_TIME_1-BIT_TIME_FUZZ) && time < (BIT_TIME_1+BIT_TIME_FUZZ)) {
-					/* 1 bit */
-					emit(1);
-					active = 1;
-					LED_B_ON();
-				} else if(time > (BIT_TIME_0-BIT_TIME_FUZZ) && time < (BIT_TIME_0+BIT_TIME_FUZZ)) {
-					/* 0 bit */
-					emit(0);
-					active = 1;
-					LED_B_ON();
-				} else if(active) {
-					/* invalid */
-					emit(-1);
-					active = 0;
-					LED_B_OFF();
-				}
-			}
-		}
-		
-		if(time >= (BIT_TIME_1+BIT_TIME_FUZZ) && active) {
-			/* Frame end */
-			emit(-1);
-			active = 0;
-			LED_B_OFF();
-		}
+		LED_A_ON();
+		frame_send_rwd(queries[0].data, queries[0].bits);
+		LED_A_OFF();
 		
-		if(time >= (20*BIT_TIME_1) && (AT91C_BASE_TC1->TC_SR & AT91C_TC_CLKSTA)) {
-			AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
-		}
+		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);
 		
-		old_level = level;
 		WDT_HIT();
 	}
+	
 }