方案：单片机处于低功耗模式，MS522处于软掉电模式。单片机用RTC定时（比如每隔1s）唤醒，单片机唤醒后唤醒MS522寻卡。寻到卡则做进一步处理，否则MS522继续进入软掉电模式，单片机进入低功耗模式。
if ( == flag_rtc_wakeup)
{
flag_rtc_wakeup = ; pcd_soft_powerup(); if (pcd_fast_detect() == true)
{
//todo
} pcd_soft_powerdown();
}
void pcd_soft_powerdown(void)
{
write_rawrc(CommandReg, PCD_NOCMDCHANGE | ( << ));
} void pcd_soft_powerup(void)
{
uint8_t count = ; write_rawrc(CommandReg, PCD_NOCMDCHANGE & (~( << )));
do
{
// Wait for the PowerDown bit in CommandReg to be cleared (max 3x10us)
delay_10us();
} while ((read_rawrc(CommandReg) & ( << )) && (++count) < );
}
手册相关内容
//快速寻卡函数
bool pcd_fast_detect(void)
{
uint8_t valid_bits = ;
uint8_t command = PICC_REQIDL;
uint8_t wait_irq = 0x30; // RxIRq and IdleIRq
uint8_t n;
uint16_t i; clear_bit_mask(CollReg, 0x80); // valuesAfterColl=1 => Bits received after collision are cleared. // write_rawrc(CommandReg, PCD_IDLE); // Stop any active command.
write_rawrc(ComIrqReg, 0x7F); // Clear all seven interrupt request bits
set_bit_mask(FIFOLevelReg, 0x80); // FlushBuffer = 1, FIFO initialization
write_rawrc(FIFODataReg, command); // Write sendData to the FIFO
write_rawrc(BitFramingReg, valid_bits); // Bit adjustments
write_rawrc(CommandReg, PCD_TRANSCEIVE); // Execute the command
set_bit_mask(BitFramingReg, 0x80); // StartSend=1, transmission of data starts i = ; //根据时钟频率修改
while ()
{
n = read_rawrc(ComIrqReg); // ComIrqReg[7..0] bits are: Set1 TxIRq RxIRq IdleIRq HiAlertIRq LoAlertIRq ErrIRq TimerIRq
if (n & wait_irq)
{ // One of the interrupts that signal success has been set.
//debug("t\r\n");
break;
}
if (n & 0x01)
{ // Timer interrupt - nothing received in time
//debug("f\r\n");
return false;
}
if (--i == )
{ // The emergency break. If all other conditions fail we will eventually terminate on this one. Communication with the MFRC522 might be down.
//debug("i\r\n");
return false;
}
} return true;
}
void pcd_reset(void)
{
RC522_RST_ON;
write_rawrc(CommandReg, PCD_RESETPHASE);
uint8_t count = ;
do
{
// Wait for the PowerDown bit in CommandReg to be cleared (max 3x40us)
delay_10us();
} while ((read_rawrc(CommandReg) & ( << )) && (++count) < );
// TAuto=1; timer starts automatically at the end of the transmission in all communication modes at all speeds.10us
write_rawrc(TModeReg, 0x80);
write_rawrc(TPrescalerReg, 0x43); // 10μs
// Reload timer with 0x1e = 30, ie 0.3ms before timeout.
write_rawrc(TReloadRegH, 0x00);
write_rawrc(TReloadRegL, 0x1e); write_rawrc(TxAutoReg, 0x40);
write_rawrc(ModeReg, 0x3d); //和Mifare卡通讯，CRC初始值0x6363 pcd_antenna_on();
}
参考资料：
MS522手册：https://wenku.baidu.com/view/6f5bcabcbcd126fff6050b77
关于软掉电模式的讨论：https://github.com/miguelbalboa/rfid/issues/269
软掉电模式DEMO：https://github.com/akellai/rfid-music/blob/master/RFID_ProMini/RFID_ProMini.ino