MS522低功耗寻卡

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