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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);
}
}
}
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