github/RRG-Proxmark3
1
0
Fork 0
mirror of https://github.com/RfidResearchGroup/proxmark3.git synced 2025-08-14 10:37:23 -07:00
Code Issues Projects Releases Packages Wiki Activity Actions

change: switched from timestamps (us) to ticks

Browse source 
GetCountUS() has a jitter of +/- 7us this is not precise
enough to keep the PRNG in sync. 1.5 * GET_TICKS on the
other hand is spot on.
This commit is contained in:
Andreas Dröscher 2018-08-09 09:32:14 +02:00
commit c06f0af7f3
1 changed files with 18 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

34
armsrc/legicrf.c
View file

@ -31,7 +31,7 @@ static int32_t input_threshold; /* values > threshold are 1 else 0 */
//
// The data dependent timing makes writing comprehensible code significantly
// harder. The current aproach forwards the prng data based if there is data on
// air and time based, using GetCountUS(), during computational and wait periodes.
// air and time based, using GET_TICKS, during computational and wait periodes.
//
// To not have the necessity to calculate/guess exection time dependend timeouts
// tx_frame and rx_frame use a shared timestamp to coordinate tx and rx timeslots.
@ -39,12 +39,12 @@ static int32_t input_threshold; /* values > threshold are 1 else 0 */
static uint32_t last_frame_end; /* ts of last bit of previews rx or tx frame */
#define RWD_TIME_PAUSE 20 /* 20us */
#define RWD_TIME_1 100 /* READER_TIME_PAUSE 20us off + 80us on = 100us */
#define RWD_TIME_0 60 /* READER_TIME_PAUSE 20us off + 40us on = 60us */
#define RWD_FRAME_WAIT 220 /* 220us from TAG frame end to READER frame start */
#define TAG_FRAME_WAIT 330 /* 330us from READER frame end to TAG frame start */
#define TAG_BIT_PERIOD 100 /* 100us */
#define RWD_TIME_PAUSE 30 /* 20us */
#define RWD_TIME_1 150 /* READER_TIME_PAUSE 20us off + 80us on = 100us */
#define RWD_TIME_0 90 /* READER_TIME_PAUSE 20us off + 40us on = 60us */
#define RWD_FRAME_WAIT 330 /* 220us from TAG frame end to READER frame start */
#define TAG_FRAME_WAIT 495 /* 330us from READER frame end to TAG frame start */
#define TAG_BIT_PERIOD 150 /* 100us */
#define LEGIC_CARD_MEMSIZE 1024 /* The largest Legic Prime card is 1k */
@ -123,12 +123,12 @@ static inline void tx_bit(bool bit) {
// insert pause
LOW(GPIO_SSC_DOUT);
last_frame_end += RWD_TIME_PAUSE;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
HIGH(GPIO_SSC_DOUT);
// return to high, wait for bit periode to end
last_frame_end += (bit ? RWD_TIME_1 : RWD_TIME_0) - RWD_TIME_PAUSE;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
}
//-----------------------------------------------------------------------------
@ -146,7 +146,7 @@ static void tx_frame(uint32_t frame, uint8_t len) {
// wait for next tx timeslot
last_frame_end += RWD_FRAME_WAIT;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
// transmit frame, MSB first
for(uint8_t i = 0; i < len; ++i) {
@ -158,7 +158,7 @@ static void tx_frame(uint32_t frame, uint8_t len) {
// add pause to mark end of the frame
LOW(GPIO_SSC_DOUT);
last_frame_end += RWD_TIME_PAUSE;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
HIGH(GPIO_SSC_DOUT);
}
@ -169,7 +169,7 @@ static uint32_t rx_frame(uint8_t len) {
// hold sampling until card is expected to respond
last_frame_end += TAG_FRAME_WAIT;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
uint32_t frame = 0;
for(uint8_t i = 0; i < len; i++) {
@ -178,7 +178,7 @@ static uint32_t rx_frame(uint8_t len) {
// rx_bit runs only 95us, resync to TAG_BIT_PERIOD
last_frame_end += TAG_BIT_PERIOD;
while(GetCountUS() < last_frame_end) { };
while(GET_TICKS < last_frame_end) { };
}
return frame;
@ -246,7 +246,7 @@ static void init_reader(bool clear_mem) {
crc_init(&legic_crc, 4, 0x19 >> 1, 0x05, 0);
// start us timer
StartCountUS();
StartTicks();
}
// Setup reader to card connection
@ -257,7 +257,7 @@ static void init_reader(bool clear_mem) {
// - Acknowledge frame 6 bits
static uint32_t setup_phase_reader(uint8_t iv) {
// init coordination timestamp
last_frame_end = GetCountUS();
last_frame_end = GET_TICKS;
// Switch on carrier and let the card charge for 5ms.
// Use the time to calibrate the treshhold.
@ -267,7 +267,7 @@ static uint32_t setup_phase_reader(uint8_t iv) {
if(sample > input_threshold) {
input_threshold = sample;
}
} while(GetCountUS() < last_frame_end + 5000);
} while(GET_TICKS < last_frame_end + 7500);
// Set threshold to noise floor * 2
input_threshold <<= 1;
@ -367,6 +367,7 @@ void LegicRfInfo(void) {
OUT:
switch_off();
StopTicks();
}
void LegicRfReader(uint16_t offset, uint16_t len, uint8_t iv) {
@ -399,6 +400,7 @@ void LegicRfReader(uint16_t offset, uint16_t len, uint8_t iv) {
OUT:
switch_off();
StopTicks();
}
void LegicRfWriter(uint16_t offset, uint16_t len, uint8_t iv, uint8_t *data) {