github/RRG-Proxmark3
1
0
Fork 0
mirror of https://github.com/RfidResearchGroup/proxmark3.git synced 2025-08-21 22:03:42 -07:00
Code Issues Projects Releases Packages Wiki Activity Actions

em4x70: clean up edge detection code

Browse source
This commit is contained in:
Christian Molson 2020-12-13 16:23:25 -05:00
commit f87aa869c6
2 changed files with 44 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

90
armsrc/em4x70.c
View file

@ -130,36 +130,27 @@ static bool get_signalproperties(void) {
} }
/** /**
* get_pulse_length * get_falling_pulse_length
* *
* Times falling edge pulses * Returns time between falling edge pulse in ticks
*/ */
static uint32_t get_pulse_length(void) { static uint32_t get_falling_pulse_length(void) {
uint8_t sample;
uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT; uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
do { while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
uint32_t start_ticks = GetTicks(); uint32_t start_ticks = GetTicks();
timeout = start_ticks + EM4X70_T_TAG_TIMEOUT;
do { while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT; while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
do {
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
@ -168,37 +159,27 @@ static uint32_t get_pulse_length(void) {
} }
/** /**
* get_pulse_invert_length * get_rising_pulse_length
* *
* Times rising edge pules * Returns time between rising edge pulse in ticks
* TODO: convert to single function with get_pulse_length()
*/ */
static uint32_t get_pulse_invert_length(void) { static uint32_t get_rising_pulse_length(void) {
uint8_t sample;
uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT; uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
do { while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
uint32_t start_ticks = GetTicks(); uint32_t start_ticks = GetTicks();
timeout = start_ticks + EM4X70_T_TAG_TIMEOUT;
do { while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT; while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
do {
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
if (IS_TIMEOUT(timeout)) if (IS_TIMEOUT(timeout))
return 0; return 0;
@ -207,6 +188,16 @@ static uint32_t get_pulse_invert_length(void) {
} }
static uint32_t get_pulse_length(edge_detection_t edge) {
if(edge == RISING_EDGE)
return get_rising_pulse_length();
else if(edge == FALLING_EDGE)
return get_falling_pulse_length();
return 0;
}
static bool check_pulse_length(uint32_t pl, uint32_t length) { static bool check_pulse_length(uint32_t pl, uint32_t length) {
// check if pulse length <pl> corresponds to given length <length> // check if pulse length <pl> corresponds to given length <length>
return ((pl >= (length - EM4X70_T_TAG_TOLERANCE)) & (pl <= (length + EM4X70_T_TAG_TOLERANCE))); return ((pl >= (length - EM4X70_T_TAG_TOLERANCE)) & (pl <= (length + EM4X70_T_TAG_TOLERANCE)));
@ -309,10 +300,10 @@ static bool check_ack(void) {
64 (48+16) 64 (48+16)
48 (32+16) 48 (32+16)
*/ */
if (check_pulse_length(get_pulse_length(), 2 * EM4X70_T_TAG_FULL_PERIOD)) { if (check_pulse_length(get_pulse_length(FALLING_EDGE), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
// The received signal is either ACK or NAK. // The received signal is either ACK or NAK.
if (check_pulse_length(get_pulse_length(), 2 * EM4X70_T_TAG_FULL_PERIOD)) { if (check_pulse_length(get_pulse_length(FALLING_EDGE), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
return true; return true;
} else { } else {
// It's NAK -> stop searching // It's NAK -> stop searching
@ -448,10 +439,10 @@ static bool find_listen_window(bool command) {
96 ( 64 + 32 ) 96 ( 64 + 32 )
64 ( 32 + 16 +16 )*/ 64 ( 32 + 16 +16 )*/
if (check_pulse_length(get_pulse_invert_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) && if (check_pulse_length(get_pulse_length(RISING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
check_pulse_length(get_pulse_invert_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) && check_pulse_length(get_pulse_length(RISING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
check_pulse_length(get_pulse_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD) && check_pulse_length(get_pulse_length(FALLING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD) &&
check_pulse_length(get_pulse_length(), EM4X70_T_TAG_FULL_PERIOD + (2*EM4X70_T_TAG_HALF_PERIOD))) { check_pulse_length(get_pulse_length(FALLING_EDGE), EM4X70_T_TAG_FULL_PERIOD + (2*EM4X70_T_TAG_HALF_PERIOD))) {
if (command) { if (command) {
/* Here we are after the 64 duration edge. /* Here we are after the 64 duration edge.
@ -569,7 +560,7 @@ static int em4x70_receive(uint8_t *bits) {
uint32_t pl; uint32_t pl;
int bit_pos = 0; int bit_pos = 0;
uint8_t edge = 0; edge_detection_t edge = RISING_EDGE;
bool foundheader = false; bool foundheader = false;
// Read out the header // Read out the header
@ -582,7 +573,7 @@ static int em4x70_receive(uint8_t *bits) {
// wait until we get the transition from 1's to 0's which is 1.5 full windows // wait until we get the transition from 1's to 0's which is 1.5 full windows
int pulse_count = 0; int pulse_count = 0;
while (pulse_count < 12) { while (pulse_count < 12) {
pl = get_pulse_invert_length(); pl = get_pulse_length(edge);
pulse_count++; pulse_count++;
if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) { if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) {
foundheader = true; foundheader = true;
@ -597,40 +588,37 @@ static int em4x70_receive(uint8_t *bits) {
// Skip next 3 0's, header check consumes the first 0 // Skip next 3 0's, header check consumes the first 0
for (int i = 0; i < 3; i++) { for (int i = 0; i < 3; i++) {
get_pulse_invert_length(); get_pulse_length(edge);
} }
// identify remaining bits based on pulse lengths // identify remaining bits based on pulse lengths
// between listen windows only pulse lengths of 1, 1.5 and 2 are possible // between listen windows only pulse lengths of 1, 1.5 and 2 are possible
while (bit_pos < EM4X70_MAX_RECEIVE_LENGTH) { while (bit_pos < EM4X70_MAX_RECEIVE_LENGTH) {
if (edge) pl = get_pulse_length(edge);
pl = get_pulse_length();
else
pl = get_pulse_invert_length();
if (check_pulse_length(pl, EM4X70_T_TAG_FULL_PERIOD)) { if (check_pulse_length(pl, EM4X70_T_TAG_FULL_PERIOD)) {
// pulse length = 1 // pulse length = 1
bits[bit_pos++] = edge; bits[bit_pos++] = edge == FALLING_EDGE ? 1 : 0;
} else if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) { } else if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) {
// pulse length = 1.5 -> flip edge detection // pulse length = 1.5 -> flip edge detection
if (edge) { if (edge == FALLING_EDGE) {
bits[bit_pos++] = 0; bits[bit_pos++] = 0;
bits[bit_pos++] = 0; bits[bit_pos++] = 0;
edge = 0; edge = RISING_EDGE;
} else { } else {
bits[bit_pos++] = 1; bits[bit_pos++] = 1;
bits[bit_pos++] = 1; bits[bit_pos++] = 1;
edge = 1; edge = FALLING_EDGE;
} }
} else if (check_pulse_length(pl, 2 * EM4X70_T_TAG_FULL_PERIOD)) { } else if (check_pulse_length(pl, 2 * EM4X70_T_TAG_FULL_PERIOD)) {
// pulse length of 2 // pulse length of 2
if (edge) { if (edge == FALLING_EDGE) {
bits[bit_pos++] = 0; bits[bit_pos++] = 0;
bits[bit_pos++] = 1; bits[bit_pos++] = 1;
} else { } else {
@ -638,8 +626,8 @@ static int em4x70_receive(uint8_t *bits) {
bits[bit_pos++] = 0; bits[bit_pos++] = 0;
} }
} else if ((edge && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD)) || } else if (((edge == FALLING_EDGE) && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD)) ||
(!edge && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD))) { ((edge == RISING_EDGE) && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD))) {
// LIW detected (either invert or normal) // LIW detected (either invert or normal)
return --bit_pos; return --bit_pos;

5
armsrc/em4x70.h
View file

@ -17,6 +17,11 @@ typedef struct {
uint8_t data[32]; uint8_t data[32];
} em4x70_tag_t; } em4x70_tag_t;
typedef enum {
RISING_EDGE,
FALLING_EDGE
}edge_detection_t;
void em4x70_info(em4x70_data_t *etd); void em4x70_info(em4x70_data_t *etd);
void em4x70_write(em4x70_data_t *etd); void em4x70_write(em4x70_data_t *etd);
void em4x70_unlock(em4x70_data_t *etd); void em4x70_unlock(em4x70_data_t *etd);