我将STM32微处理器与RFID EM4095配合使用，试图读取RFID卡，但同步总是很差。我正在为DMOUD_OUT，RDY_CLK信号使用2个中断。这是我正在采取的步骤：
等待DMOD_OUT的下降沿并禁用DMOD_out中断并启用RDYCLCK中断。
等待RDYCLK上的16个上升沿。
从dmod中获取1位
等待RDYCLK上的32个上升沿。
从dmodout中获取1位（请与它的前任（bit == predessor？bad_sync = 1）进行核对）
重复4和5以获得127位。
主要功能：
volatile char cnt = 0;
static volatile unsigned char dump_last = 0;
static volatile unsigned char aux = 0;
static volatile unsigned char count = 0;
static volatile unsigned char latch = 0;
static volatile unsigned char page = 0;
volatile char sync_flag = 0;
static volatile unsigned char finish = 0;
unsigned char buf[128];
int // in the sync routine if this flag is set
one_seq, // counts the number of 'logic one' in series
data_in, // gets data bit depending on data_in_1st and data_in_2nd
// interrupt counter
cnt1, cnt2; // auxiliary counters
volatile unsigned short data_index; // marks position in data arrey
volatile unsigned char i;
volatile unsigned char _data[256];
volatile unsigned char data_valid[64];
volatile unsigned char bad_synch;
int main(void) {
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_NVIC_Init();
HAL_GPIO_WritePin(GPIOA, SHD_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(GPIOA, MOD_Pin, GPIO_PIN_SET);
sync_flag = 0; // sync_flag is set when falling edge on RB0 is detected
one_seq = 0; // counts the number of 'logic one' in series
data_in = 0; // gets data bit
data_index = 0; // marks position in data arrey
cnt = 0; // interrupt counter
cnt1 = 0; // auxiliary counter
cnt2 = 0; // auxiliary counter
while (1) {
HAL_NVIC_DisableIRQ(EXTI15_10_IRQn);
HAL_NVIC_DisableIRQ(EXTI3_IRQn);
HAL_GPIO_WritePin(GPIOA, SHD_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(GPIOA, MOD_Pin, GPIO_PIN_SET);
bad_synch = 0; // set bad synchronization variable to zero
cnt = 0; // reseting interrupt counter
sync_flag = 0; // reseting sync flag
HAL_NVIC_DisableIRQ(EXTI15_10_IRQn);
HAL_NVIC_EnableIRQ(EXTI3_IRQn);
HAL_GPIO_WritePin(GPIOA, MOD_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(GPIOA, SHD_Pin, GPIO_PIN_RESET);
while (sync_flag == 0) { // waiting for falling edge on RB0
__nop();
}
while (cnt != 16) { // waiting 16 clocks on RB1 (positioning for 1sampling)
__nop();
}
cnt = 0;
_data[0] = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_3);
for (data_index = 1; data_index != 0; data_index++) { // getting 128 bits of data from RB0
while (cnt !=32) { // getting bit from RB0 every 32 clocks on RB1
__nop();
}
cnt = 0; // reseting interrupt counter
_data[data_index] =HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_3); // geting bit
if (data_index & 1)
if (!(_data[data_index] != _data[data_index - 1])) {
bad_synch = 1;
//GLCD_WriteChar('B');
break; //bad synchronisation
}
}
if (bad_synch)
{
HAL_GPIO_TogglePin(GPIOB,GPIO_PIN_0);
continue; // try again
}
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_8,GPIO_PIN_SET);
HAL_NVIC_DisableIRQ(EXTI15_10_IRQn);
cnt1 = 0;
one_seq = 0;
for (cnt1 = 0; cnt1 <= 127; cnt1++) { // we are counting 'logic one' in the data array
if (_data[cnt1 << 1] == 1) {
one_seq++;
} else {
one_seq = 0;
}
if (one_seq == 9) { // if we get 9 'logic one' we break from the loop
break;
}
}
if ((one_seq == 9) && (cnt1 < 73)) { // if we got 9 'logic one' before cnt1 position 73
// we write that data into data_valid array
data_valid[0] = 1; // (it has to be before cnt1 position 73 in order
data_valid[1] = 1; // to have all 64 bits available in data array)
data_valid[2] = 1;
data_valid[3] = 1;
data_valid[4] = 1;
data_valid[5] = 1;
data_valid[6] = 1;
data_valid[7] = 1;
data_valid[8] = 1;
for (cnt2 = 9; cnt2 <= 63; cnt2++) { // copying the rest of data from the data array into data_valid array
cnt1++;
data_valid[cnt2] = _data[cnt1 << 1];
}
if (1) { // if data in data_valid array pass the CRC check
for (i = 0; i <= 64; i++) { // This part of the code
// dislays the number of the specific RfID CARD
if (data_valid[i] == 0) {
GLCD_WriteChar('0');
} else {
GLCD_WriteChar('1'); // at the end of this for loop you will get a string of "0" and "1"
}
} // specific to a single RfID CARD
}
}
HAL_Delay(5000);
HAL_NVIC_EnableIRQ(EXTI3_IRQn);
}
}
中断处理程序：
void HAL_GPIO_EXTI_IRQHandler(uint16_t GPIO_Pin) {
if (GPIO_Pin == RDYCLK_Pin) {
cnt++;
}
else if (GPIO_Pin == DMOD_Pin) {
sync_flag = 1;
HAL_NVIC_DisableIRQ(EXTI3_IRQn);
HAL_NVIC_EnableIRQ(EXTI15_10_IRQn);
}
__HAL_GPIO_EXTI_CLEAR_IT(GPIO_Pin);
}