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https://github.com/RfidResearchGroup/proxmark3.git
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em4x70: clean up edge detection code
This commit is contained in:
Christian Molson
parent
7a01ba90c5
commit
f87aa869c6
2 changed files with 44 additions and 51 deletions
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@ -130,36 +130,27 @@ static bool get_signalproperties(void) {
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}
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/**
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* get_pulse_length
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* get_falling_pulse_length
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*
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* Times falling edge pulses
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* Returns time between falling edge pulse in ticks
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*/
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static uint32_t get_pulse_length(void) {
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static uint32_t get_falling_pulse_length(void) {
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uint8_t sample;
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uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
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while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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uint32_t start_ticks = GetTicks();
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timeout = start_ticks + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
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while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
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while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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@ -168,37 +159,27 @@ static uint32_t get_pulse_length(void) {
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}
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/**
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* get_pulse_invert_length
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* get_rising_pulse_length
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*
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* Times rising edge pules
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* TODO: convert to single function with get_pulse_length()
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* Returns time between rising edge pulse in ticks
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*/
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static uint32_t get_pulse_invert_length(void) {
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static uint32_t get_rising_pulse_length(void) {
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uint8_t sample;
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uint32_t timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
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while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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uint32_t start_ticks = GetTicks();
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timeout = start_ticks + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_HIGH(sample) && !IS_TIMEOUT(timeout));
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while (IS_HIGH(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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timeout = GetTicks() + EM4X70_T_TAG_TIMEOUT;
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do {
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sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
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} while (IS_LOW(sample) && !IS_TIMEOUT(timeout));
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while (IS_LOW(AT91C_BASE_SSC->SSC_RHR) && !IS_TIMEOUT(timeout));
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if (IS_TIMEOUT(timeout))
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return 0;
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@ -207,6 +188,16 @@ static uint32_t get_pulse_invert_length(void) {
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}
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static uint32_t get_pulse_length(edge_detection_t edge) {
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if(edge == RISING_EDGE)
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return get_rising_pulse_length();
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else if(edge == FALLING_EDGE)
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return get_falling_pulse_length();
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return 0;
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}
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static bool check_pulse_length(uint32_t pl, uint32_t length) {
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// check if pulse length <pl> corresponds to given length <length>
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return ((pl >= (length - EM4X70_T_TAG_TOLERANCE)) & (pl <= (length + EM4X70_T_TAG_TOLERANCE)));
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@ -309,10 +300,10 @@ static bool check_ack(void) {
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64 (48+16)
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48 (32+16)
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*/
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if (check_pulse_length(get_pulse_length(), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
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if (check_pulse_length(get_pulse_length(FALLING_EDGE), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
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// The received signal is either ACK or NAK.
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if (check_pulse_length(get_pulse_length(), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
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if (check_pulse_length(get_pulse_length(FALLING_EDGE), 2 * EM4X70_T_TAG_FULL_PERIOD)) {
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return true;
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} else {
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// It's NAK -> stop searching
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@ -448,10 +439,10 @@ static bool find_listen_window(bool command) {
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96 ( 64 + 32 )
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64 ( 32 + 16 +16 )*/
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if (check_pulse_length(get_pulse_invert_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
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check_pulse_length(get_pulse_invert_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
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check_pulse_length(get_pulse_length(), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD) &&
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check_pulse_length(get_pulse_length(), EM4X70_T_TAG_FULL_PERIOD + (2*EM4X70_T_TAG_HALF_PERIOD))) {
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if (check_pulse_length(get_pulse_length(RISING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
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check_pulse_length(get_pulse_length(RISING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD) &&
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check_pulse_length(get_pulse_length(FALLING_EDGE), (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD) &&
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check_pulse_length(get_pulse_length(FALLING_EDGE), EM4X70_T_TAG_FULL_PERIOD + (2*EM4X70_T_TAG_HALF_PERIOD))) {
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if (command) {
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/* Here we are after the 64 duration edge.
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@ -569,7 +560,7 @@ static int em4x70_receive(uint8_t *bits) {
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uint32_t pl;
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int bit_pos = 0;
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uint8_t edge = 0;
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edge_detection_t edge = RISING_EDGE;
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bool foundheader = false;
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// Read out the header
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@ -582,7 +573,7 @@ static int em4x70_receive(uint8_t *bits) {
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// wait until we get the transition from 1's to 0's which is 1.5 full windows
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int pulse_count = 0;
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while (pulse_count < 12) {
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pl = get_pulse_invert_length();
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pl = get_pulse_length(edge);
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pulse_count++;
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if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) {
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foundheader = true;
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@ -597,40 +588,37 @@ static int em4x70_receive(uint8_t *bits) {
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// Skip next 3 0's, header check consumes the first 0
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for (int i = 0; i < 3; i++) {
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get_pulse_invert_length();
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get_pulse_length(edge);
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}
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// identify remaining bits based on pulse lengths
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// between listen windows only pulse lengths of 1, 1.5 and 2 are possible
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while (bit_pos < EM4X70_MAX_RECEIVE_LENGTH) {
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if (edge)
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pl = get_pulse_length();
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else
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pl = get_pulse_invert_length();
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pl = get_pulse_length(edge);
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if (check_pulse_length(pl, EM4X70_T_TAG_FULL_PERIOD)) {
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// pulse length = 1
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bits[bit_pos++] = edge;
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bits[bit_pos++] = edge == FALLING_EDGE ? 1 : 0;
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} else if (check_pulse_length(pl, 3 * EM4X70_T_TAG_HALF_PERIOD)) {
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// pulse length = 1.5 -> flip edge detection
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if (edge) {
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if (edge == FALLING_EDGE) {
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bits[bit_pos++] = 0;
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bits[bit_pos++] = 0;
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edge = 0;
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edge = RISING_EDGE;
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} else {
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bits[bit_pos++] = 1;
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bits[bit_pos++] = 1;
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edge = 1;
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edge = FALLING_EDGE;
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}
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} else if (check_pulse_length(pl, 2 * EM4X70_T_TAG_FULL_PERIOD)) {
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// pulse length of 2
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if (edge) {
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if (edge == FALLING_EDGE) {
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bits[bit_pos++] = 0;
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bits[bit_pos++] = 1;
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} else {
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@ -638,8 +626,8 @@ static int em4x70_receive(uint8_t *bits) {
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bits[bit_pos++] = 0;
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}
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} else if ((edge && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD)) ||
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(!edge && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD))) {
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} else if (((edge == FALLING_EDGE) && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_FULL_PERIOD)) ||
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((edge == RISING_EDGE) && check_pulse_length(pl, (2*EM4X70_T_TAG_FULL_PERIOD) + EM4X70_T_TAG_HALF_PERIOD))) {
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// LIW detected (either invert or normal)
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return --bit_pos;
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@ -17,6 +17,11 @@ typedef struct {
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uint8_t data[32];
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} em4x70_tag_t;
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typedef enum {
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RISING_EDGE,
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FALLING_EDGE
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}edge_detection_t;
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void em4x70_info(em4x70_data_t *etd);
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void em4x70_write(em4x70_data_t *etd);
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void em4x70_unlock(em4x70_data_t *etd);
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