1 files changed, 143 insertions, 0 deletions
diff --git a/openpicc/application/tc_sniffer.c b/openpicc/application/tc_sniffer.c
new file mode 100644
index 0000000..abf04c0
--- /dev/null
+++ b/openpicc/application/tc_sniffer.c
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+/***************************************************************
+ *
+ * OpenPICC - T/C based dumb sniffer
+ * 
+ * TC2 will reset its value on each falling edge of SSC_DATA, we
+ * will have the FIQ store the TC2 value on each rising edge of
+ * SSC_DATA. This will give us a count of carrier cycles between
+ * modulation pauses which should be enough information to decode
+ * the modified miller encoding.
+ *
+ * Copyright 2008 Henryk Plötz <henryk@ploetzli.ch>
+ *
+ ***************************************************************
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; version 2.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+*/
+
+#include <FreeRTOS.h>
+#include <openpicc.h>
+#include <task.h>
+#include <string.h>
+
+#include <USB-CDC.h>
+
+#include "tc_sniffer.h"
+#include "load_modulation.h"
+#include "pll.h"
+#include "tc_fdt.h"
+#include "usb_print.h"
+#include "cmd.h"
+#include "pio_irq.h"
+
+/* Problem: We want to receive data from the FIQ without locking (the FIQ must not be blocked ever)
+ * Strategy: Double buffering.
+ */
+
+#define BUFSIZE 1024
+#define WAIT_TICKS (20*portTICK_RATE_MS)
+typedef struct {
+	u_int32_t count;
+	u_int32_t data[BUFSIZE];
+} fiq_buffer_t;
+fiq_buffer_t fiq_buffers[2];
+
+fiq_buffer_t *tc_sniffer_next_buffer_for_fiq = 0;
+
+portBASE_TYPE currently_sniffing = 0;
+enum { NONE, REQUEST_START, REQUEST_STOP } request_change = NONE;
+
+#define MIN(a, b) ((a)>(b)?(b):(a))
+void flush_buffer(fiq_buffer_t *buffer)
+{
+	/* Write all data from the given buffer out, then zero the count */
+	if(buffer->count > 0) {
+		vUSBSendBuffer_blocking((unsigned char*)(&(buffer->data[0])), 0, MIN(buffer->count,BUFSIZE)*4, WAIT_TICKS);
+		if(buffer->count >= BUFSIZE)
+			vUSBSendBuffer_blocking((unsigned char*)"////", 0, 4, WAIT_TICKS);
+		else
+			vUSBSendBuffer_blocking((unsigned char*)"____", 0, 4, WAIT_TICKS);
+		buffer->count = 0;
+	}
+}
+
+void start_stop_sniffing(void)
+{
+	if(currently_sniffing)
+		request_change = REQUEST_STOP;
+	else
+		request_change = REQUEST_START;
+}
+
+void tc_sniffer (void *pvParameters)
+{
+	(void)pvParameters;
+	
+	/* Disable load modulation circuitry
+	 * (Must be done explicitly, because the default state is pull-up high, leading
+	 * to a constant modulation output which prevents reception. I've been bitten by
+	 * this more than once.)
+	 */
+	load_mod_init();
+	load_mod_level(0);
+	
+	pll_init();
+	pll_inhibit(0);
+	
+	tc_fdt_init();
+	
+	memset(fiq_buffers, 0, sizeof(fiq_buffers));
+	
+	/* Wait for the USB and CMD threads to start up */
+	vTaskDelay(1000 * portTICK_RATE_MS);
+	
+	// The change interrupt is going to be handled by the FIQ 
+	AT91F_PIO_CfgInput(AT91C_BASE_PIOA, OPENPICC_SSC_DATA);
+	pio_irq_enable(OPENPICC_SSC_DATA);
+	
+	int current = 0;
+	while(1) {
+		/* Main loop of the sniffer */
+		
+		if(currently_sniffing) {
+			int next = (current+1)%(sizeof(fiq_buffers)/sizeof(fiq_buffers[0]));
+			flush_buffer( &fiq_buffers[next] );
+			/* The buffer designated by next is now empty, give it to the fiq,
+			 * we'll just guess that this write is atomic */ 
+			tc_sniffer_next_buffer_for_fiq = &fiq_buffers[current=next];
+
+			if(request_change == REQUEST_STOP) {
+				currently_sniffing = 0;
+				request_change = NONE;
+				
+				tc_sniffer_next_buffer_for_fiq = 0;
+				memset(fiq_buffers, 0, sizeof(fiq_buffers));
+				current = 0;
+				vUSBSendBuffer_blocking((unsigned char *)"----", 0, 4, WAIT_TICKS);
+				usb_print_set_force_silence(0);
+			} else vTaskDelay(2* portTICK_RATE_MS);
+		} else {
+			// Do nothing, wait longer
+			
+			if(request_change == REQUEST_START) {
+				// Prevent usb_print code from barging in
+				usb_print_set_force_silence(1);
+				vUSBSendBuffer_blocking((unsigned char *)"----", 0, 4, WAIT_TICKS);
+				currently_sniffing = 1;
+				request_change = NONE;
+			} else vTaskDelay(100 * portTICK_RATE_MS);
+		}
+	}
+}