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proxmark3/armsrc/legicrf.c

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//-----------------------------------------------------------------------------
// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
//
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// LEGIC RF simulation code
//-----------------------------------------------------------------------------
#include "proxmark3.h"
#include "apps.h"
#include "util.h"
#include "string.h"
#include "legicrf.h"
#include "legic_prng.h"
#include "crc.h"
static struct legic_frame {
int bits;
uint32_t data;
} current_frame;
static enum {
STATE_DISCON,
STATE_IV,
STATE_CON,
} legic_state;
static crc_t legic_crc;
static int legic_read_count;
static uint32_t legic_prng_bc;
static uint32_t legic_prng_iv;
static int legic_phase_drift;
static int legic_frame_drift;
static int legic_reqresp_drift;
AT91PS_TC timer;
AT91PS_TC prng_timer;
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 = AT91C_TC_CLKS_TIMER_DIV3_CLOCK;
timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
/*
* Set up Timer 2 to use for measuring time between frames in
* tag simulation mode. Runs 4x faster as Timer 1
*/
AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC2);
prng_timer = AT91C_BASE_TC2;
prng_timer->TC_CCR = AT91C_TC_CLKDIS;
prng_timer->TC_CMR = AT91C_TC_CLKS_TIMER_DIV2_CLOCK;
prng_timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
}
/* 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 */
#define SIM_DIVISOR 586 /* prng_time/SIM_DIVISOR count prng needs to be forwared */
#define SIM_SHIFT 900 /* prng_time+SIM_SHIFT shift of delayed start */
#define SESSION_IV 0x55
#define OFFSET_LOG 1024
#define FUZZ_EQUAL(value, target, fuzz) ((value) > ((target)-(fuzz)) && (value) < ((target)+(fuzz)))
/* Generate Keystream */
static uint32_t get_key_stream(int skip, int count)
{
uint32_t key=0; int i;
/* Use int to enlarge timer tc to 32bit */
legic_prng_bc += prng_timer->TC_CV;
prng_timer->TC_CCR = AT91C_TC_SWTRG;
/* If skip == -1, forward prng time based */
if(skip == -1) {
i = (legic_prng_bc+SIM_SHIFT)/SIM_DIVISOR; /* Calculate Cycles based on timer */
i -= legic_prng_count(); /* substract cycles of finished frames */
i -= count; /* substract current frame length, rewidn to bedinning */
legic_prng_forward(i);
} else {
legic_prng_forward(skip);
}
/* Write Time Data into LOG */
if(count == 6) { i = -1; } else { i = legic_read_count; }
((uint8_t*)BigBuf)[OFFSET_LOG+128+i] = legic_prng_count();
((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4] = (legic_prng_bc >> 0) & 0xff;
((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+1] = (legic_prng_bc >> 8) & 0xff;
((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+2] = (legic_prng_bc >>16) & 0xff;
((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+3] = (legic_prng_bc >>24) & 0xff;
((uint8_t*)BigBuf)[OFFSET_LOG+384+i] = count;
/* Generate KeyStream */
for(i=0; i<count; i++) {
key |= legic_prng_get_bit() << i;
legic_prng_forward(1);
}
return key;
}
/* Send a frame in tag mode, the FPGA must have been set up by
* LegicRfSimulate
*/
static void frame_send_tag(uint16_t response, int bits, int crypt)
{
/* 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;
/* Use time to crypt frame */
if(crypt) {
legic_prng_forward(2); /* TAG_TIME_WAIT -> shift by 2 */
int i; int key = 0;
for(i=0; i<bits; i++) {
key |= legic_prng_get_bit() << i;
legic_prng_forward(1);
}
//Dbprintf("key = 0x%x", key);
response = response ^ key;
}
/* Wait for the frame start */
while(timer->TC_CV < (TAG_TIME_WAIT - 30)) ;
int i;
for(i=0; i<bits; i++) {
int nextbit = timer->TC_CV + TAG_TIME_BIT;
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(timer->TC_CV < nextbit) ;
}
AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
}
/* Send a frame in reader mode, the FPGA must have been set up by
* LegicRfReader
*/
static void frame_send_rwd(uint32_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 ^ legic_prng_get_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;
legic_prng_forward(1); /* bit duration is longest. use this time to forward the lfsr */
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;
while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
}
/* 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, int crypt)
{
uint32_t the_bit = 1; /* Use a bitmask to save on shifts */
uint32_t data=0;
int i, old_level=0, edges=0;
int next_bit_at = TAG_TIME_WAIT;
if(bits > 32) {
bits = 32;
}
AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
/* we have some time now, precompute the cipher
* since we cannot compute it on the fly while reading */
legic_prng_forward(2);
if(crypt)
{
for(i=0; i<bits; i++) {
data |= legic_prng_get_bit() << i;
legic_prng_forward(1);
}
}
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;
/* Reset the timer, to synchronize the next frame */
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
}
static void frame_append_bit(struct legic_frame * const f, int bit)
{
if(f->bits >= 31) {
return; /* Overflow, won't happen */
}
f->data |= (bit<<f->bits);
f->bits++;
}
static void frame_clean(struct legic_frame * const f)
{
f->data = 0;
f->bits = 0;
}
static uint32_t perform_setup_phase_rwd(int iv)
{
/* Switch on carrier and let the tag charge for 1ms */
AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
SpinDelay(1);
legic_prng_init(0); /* no keystream yet */
frame_send_rwd(iv, 7);
legic_prng_init(iv);
frame_clean(&current_frame);
frame_receive_rwd(&current_frame, 6, 1);
legic_prng_forward(1); /* we wait anyways */
while(timer->TC_CV < 387) ; /* ~ 258us */
frame_send_rwd(0x19, 6);
return current_frame.data;
}
static void LegicCommonInit(void) {
FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
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();
crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
}
static void switch_off_tag_rwd(void)
{
/* Switch off carrier, make sure tag is reset */
AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
SpinDelay(10);
WDT_HIT();
}
/* calculate crc for a legic command */
static int LegicCRC(int byte_index, int value, int cmd_sz) {
crc_clear(&legic_crc);
crc_update(&legic_crc, 1, 1); /* CMD_READ */
crc_update(&legic_crc, byte_index, cmd_sz-1);
crc_update(&legic_crc, value, 8);
return crc_finish(&legic_crc);
}
int legic_read_byte(int byte_index, int cmd_sz) {
int byte;
legic_prng_forward(4); /* we wait anyways */
while(timer->TC_CV < 387) ; /* ~ 258us + 100us*delay */
frame_send_rwd(1 | (byte_index << 1), cmd_sz);
frame_clean(&current_frame);
frame_receive_rwd(&current_frame, 12, 1);
byte = current_frame.data & 0xff;
if( LegicCRC(byte_index, byte, cmd_sz) != (current_frame.data >> 8) ) {
Dbprintf("!!! crc mismatch: expected %x but got %x !!!",
LegicCRC(byte_index, current_frame.data & 0xff, cmd_sz), current_frame.data >> 8);
return -1;
}
return byte;
}
/* legic_write_byte() is not included, however it's trivial to implement
* and here are some hints on what remains to be done:
*
* * assemble a write_cmd_frame with crc and send it
* * wait until the tag sends back an ACK ('1' bit unencrypted)
* * forward the prng based on the timing
*/
int legic_write_byte(int byte, int addr, int addr_sz) {
//do not write UID, CRC, DCF
if(addr <= 0x06) {
return 0;
}
//== send write command ==============================
crc_clear(&legic_crc);
crc_update(&legic_crc, 0, 1); /* CMD_WRITE */
crc_update(&legic_crc, addr, addr_sz);
crc_update(&legic_crc, byte, 8);
uint32_t crc = crc_finish(&legic_crc);
uint32_t cmd = ((crc <<(addr_sz+1+8)) //CRC
|(byte <<(addr_sz+1)) //Data
|(addr <<1) //Address
|(0x00 <<0)); //CMD = W
uint32_t cmd_sz = addr_sz+1+8+4; //crc+data+cmd
legic_prng_forward(2); /* we wait anyways */
while(timer->TC_CV < 387) ; /* ~ 258us */
frame_send_rwd(cmd, cmd_sz);
//== wait for ack ====================================
int t, old_level=0, edges=0;
int next_bit_at =0;
while(timer->TC_CV < 387) ; /* ~ 258us */
for(t=0; t<80; t++) {
edges = 0;
next_bit_at += TAG_TIME_BIT;
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;
}
if(edges > 20 && edges < 60) { /* expected are 42 edges */
int t = timer->TC_CV;
int c = t/TAG_TIME_BIT;
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
legic_prng_forward(c);
return 0;
}
}
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
return -1;
}
int LegicRfReader(int offset, int bytes) {
int byte_index=0, cmd_sz=0, card_sz=0;
LegicCommonInit();
memset(BigBuf, 0, 1024);
DbpString("setting up legic card");
uint32_t tag_type = perform_setup_phase_rwd(SESSION_IV);
switch_off_tag_rwd(); //we lose to mutch time with dprintf
switch(tag_type) {
case 0x1d:
DbpString("MIM 256 card found, reading card ...");
cmd_sz = 9;
card_sz = 256;
break;
case 0x3d:
DbpString("MIM 1024 card found, reading card ...");
cmd_sz = 11;
card_sz = 1024;
break;
default:
Dbprintf("Unknown card format: %x",tag_type);
return -1;
}
if(bytes == -1) {
bytes = card_sz;
}
if(bytes+offset >= card_sz) {
bytes = card_sz-offset;
}
perform_setup_phase_rwd(SESSION_IV);
LED_B_ON();
while(byte_index < bytes) {
int r = legic_read_byte(byte_index+offset, cmd_sz);
if(r == -1 ||BUTTON_PRESS()) {
DbpString("operation aborted");
switch_off_tag_rwd();
LED_B_OFF();
LED_C_OFF();
return -1;
}
((uint8_t*)BigBuf)[byte_index] = r;
WDT_HIT();
byte_index++;
if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
}
LED_B_OFF();
LED_C_OFF();
switch_off_tag_rwd();
Dbprintf("Card read, use 'hf legic decode' or");
Dbprintf("'data hexsamples %d' to view results", (bytes+7) & ~7);
return 0;
}
void LegicRfWriter(int bytes, int offset) {
int byte_index=0, addr_sz=0;
LegicCommonInit();
DbpString("setting up legic card");
uint32_t tag_type = perform_setup_phase_rwd(SESSION_IV);
switch_off_tag_rwd();
switch(tag_type) {
case 0x1d:
if(offset+bytes > 0x100) {
Dbprintf("Error: can not write to 0x%03.3x on MIM 256", offset+bytes);
return;
}
addr_sz = 8;
Dbprintf("MIM 256 card found, writing 0x%02.2x - 0x%02.2x ...", offset, offset+bytes);
break;
case 0x3d:
if(offset+bytes > 0x400) {
Dbprintf("Error: can not write to 0x%03.3x on MIM 1024", offset+bytes);
return;
}
addr_sz = 10;
Dbprintf("MIM 1024 card found, writing 0x%03.3x - 0x%03.3x ...", offset, offset+bytes);
break;
default:
Dbprintf("No or unknown card found, aborting");
return;
}
LED_B_ON();
perform_setup_phase_rwd(SESSION_IV);
legic_prng_forward(2);
while(byte_index < bytes) {
int r = legic_write_byte(((uint8_t*)BigBuf)[byte_index+offset], byte_index+offset, addr_sz);
if((r != 0) || BUTTON_PRESS()) {
Dbprintf("operation aborted @ 0x%03.3x", byte_index);
switch_off_tag_rwd();
LED_B_OFF();
LED_C_OFF();
return;
}
WDT_HIT();
byte_index++;
if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
}
LED_B_OFF();
LED_C_OFF();
DbpString("write successful");
}
int timestamp;
/* Handle (whether to respond) a frame in tag mode */
static void frame_handle_tag(struct legic_frame const * const f)
{
/* First Part of Handshake (IV) */
if(f->bits == 7) {
if(f->data == SESSION_IV) {
LED_C_ON();
prng_timer->TC_CCR = AT91C_TC_SWTRG;
legic_prng_init(f->data);
frame_send_tag(0x3d, 6, 1); /* 0x3d^0x26 = 0x1b */
legic_state = STATE_IV;
legic_read_count = 0;
legic_prng_bc = 0;
legic_prng_iv = f->data;
/* TIMEOUT */
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1);
while(timer->TC_CV < 280);
return;
} else if((prng_timer->TC_CV % 50) > 40) {
legic_prng_init(f->data);
frame_send_tag(0x3d, 6, 1);
SpinDelay(20);
return;
}
}
/* 0x19==??? */
if(legic_state == STATE_IV) {
if((f->bits == 6) && (f->data == (0x19 ^ get_key_stream(1, 6)))) {
legic_state = STATE_CON;
/* TIMEOUT */
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1);
while(timer->TC_CV < 200);
return;
} else {
legic_state = STATE_DISCON;
LED_C_OFF();
Dbprintf("0x19 - Frame: %03.3x", f->data);
return;
}
}
/* Read */
if(f->bits == 11) {
if(legic_state == STATE_CON) {
int key = get_key_stream(-1, 11); //legic_phase_drift, 11);
int addr = f->data ^ key; addr = addr >> 1;
int data = ((uint8_t*)BigBuf)[addr];
int hash = LegicCRC(addr, data, 11) << 8;
((uint8_t*)BigBuf)[OFFSET_LOG+legic_read_count] = (uint8_t)addr;
legic_read_count++;
//Dbprintf("Data:%03.3x, key:%03.3x, addr: %03.3x, read_c:%u", f->data, key, addr, read_c);
legic_prng_forward(legic_reqresp_drift);
frame_send_tag(hash | data, 12, 1);
/* SHORT TIMEOUT */
timer->TC_CCR = AT91C_TC_SWTRG;
while(timer->TC_CV > 1);
legic_prng_forward(legic_frame_drift);
while(timer->TC_CV < 180);
return;
}
}
/* Write */
if(f->bits == 23) {
int key = get_key_stream(-1, 23); //legic_frame_drift, 23);
int addr = f->data ^ key; addr = addr >> 1; addr = addr & 0x3ff;
int data = f->data ^ key; data = data >> 11; data = data & 0xff;
/* write command */
legic_state = STATE_DISCON;
LED_C_OFF();
Dbprintf("write - addr: %x, data: %x", addr, data);
return;
}
if(legic_state != STATE_DISCON) {
Dbprintf("Unexpected: sz:%u, Data:%03.3x, State:%u, Count:%u", f->bits, f->data, legic_state, legic_read_count);
int i;
Dbprintf("IV: %03.3x", legic_prng_iv);
for(i = 0; i<legic_read_count; i++) {
Dbprintf("Read Nb: %u, Addr: %u", i, ((uint8_t*)BigBuf)[OFFSET_LOG+i]);
}
for(i = -1; i<legic_read_count; i++) {
uint32_t t;
t = ((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4];
t |= ((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+1] << 8;
t |= ((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+2] <<16;
t |= ((uint8_t*)BigBuf)[OFFSET_LOG+256+i*4+3] <<24;
Dbprintf("Cycles: %u, Frame Length: %u, Time: %u",
((uint8_t*)BigBuf)[OFFSET_LOG+128+i],
((uint8_t*)BigBuf)[OFFSET_LOG+384+i],
t);
}
}
legic_state = STATE_DISCON;
legic_read_count = 0;
SpinDelay(10);
LED_C_OFF();
return;
}
/* Read bit by bit untill full frame is received
* Call to process frame end answer
*/
static void emit(int bit)
{
if(bit == -1) {
if(current_frame.bits <= 4) {
frame_clean(&current_frame);
} else {
frame_handle_tag(&current_frame);
frame_clean(&current_frame);
}
WDT_HIT();
} else if(bit == 0) {
frame_append_bit(&current_frame, 0);
} else if(bit == 1) {
frame_append_bit(&current_frame, 1);
}
}
void LegicRfSimulate(int phase, int frame, int reqresp)
{
/* 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.
*/
if(phase < 0) {
int i;
for(i=0; i<=reqresp; i++) {
legic_prng_init(SESSION_IV);
Dbprintf("i=%u, key 0x%3.3x", i, get_key_stream(i, frame));
}
return;
}
legic_phase_drift = phase;
legic_frame_drift = frame;
legic_reqresp_drift = reqresp;
FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
FpgaSetupSsc();
FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_212K);
/* Bitbang the receiver */
AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
setup_timer();
crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
int old_level = 0;
int active = 0;
legic_state = STATE_DISCON;
LED_B_ON();
DbpString("Starting Legic emulator, press button to end");
while(!BUTTON_PRESS()) {
int level = !!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
int time = timer->TC_CV;
if(level != old_level) {
if(level == 1) {
timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
if(FUZZ_EQUAL(time, RWD_TIME_1, RWD_TIME_FUZZ)) {
/* 1 bit */
emit(1);
active = 1;
LED_A_ON();
} else if(FUZZ_EQUAL(time, RWD_TIME_0, RWD_TIME_FUZZ)) {
/* 0 bit */
emit(0);
active = 1;
LED_A_ON();
} else if(active) {
/* invalid */
emit(-1);
active = 0;
LED_A_OFF();
}
}
}
if(time >= (RWD_TIME_1+RWD_TIME_FUZZ) && active) {
/* Frame end */
emit(-1);
active = 0;
LED_A_OFF();
}
if(time >= (20*RWD_TIME_1) && (timer->TC_SR & AT91C_TC_CLKSTA)) {
timer->TC_CCR = AT91C_TC_CLKDIS;
}
old_level = level;
WDT_HIT();
}
DbpString("Stopped");
LED_B_OFF();
LED_A_OFF();
LED_C_OFF();
}
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