RST not works

[alex-eri]

Step 1: Describe your environment

• OS version: Ubuntu 22.04
• Arduino IDE version: PlatformIO 3.1.1
• MFRC522 Library version: 1.4.10
• Arduino device: ESP32-WROOM-32D
• MFRC522 device: XFW-ETLIVE MINI RFID-RC522

Step 2: Describe the problem

Affected file(s) or example(s):

Steps to reproduce:

I connect to module ESP32-WROOM-32D without devkit:

• io16-rst
• io17-irq
• io5-ss

Same power source AMS1117.

Init with mfrc522.PCD_Init(RFID_SS_PIN, RFID_RST_PIN);

Observed Results:

Radio chains Not starts. Cards not readed. But PCD_PerformSelfTest is OK. LOW on RFID_RST_PIN.

Expected Results:

Working reader

Relevant Code:

I make this workaround: Reader works perfect.

    pinMode(RFID_RST_PIN, OUTPUT);
    digitalWrite(RFID_RST_PIN, LOW);
    delay(2);
    digitalWrite(RFID_RST_PIN, HIGH);
    delay(2);

    mfrc522.PCD_Init(RFID_SS_PIN, 255); 
    //mfrc522.PCD_Init();

Maybe INPUT_PULLDOWN here is better?

https://github.com/miguelbalboa/rfid/blob/1e73cd34d977c5fe17fa5f2e2e8174650a572028/src/MFRC522.cpp#L208

    pinMode(_resetPowerDownPin, INPUT_PULLDOWN);

[nobur]

Hi,

I facing a similar issue and I made a similar workaround. After power on MFRC work perfectly but as soon as an esp restart is triggered ( by calling esp_restart or after an exception) it become unresponsive.

Reading the lib code, I can't understand how does this can work .

if (_resetPowerDownPin != UNUSED_PIN) {
        // First set the resetPowerDownPin as digital input, to check the MFRC522 power down mode.
        pinMode(_resetPowerDownPin, INPUT);

        if (digitalRead(_resetPowerDownPin) == LOW) {   // The MFRC522 chip is in power down mode.
            pinMode(_resetPowerDownPin, OUTPUT);        // Now set the resetPowerDownPin as digital output.
            digitalWrite(_resetPowerDownPin, LOW);      // Make sure we have a clean LOW state.
            delayMicroseconds(2);               // 8.8.1 Reset timing requirements says about 100ns. Let us be generous: 2μsl
            digitalWrite(_resetPowerDownPin, HIGH);     // Exit power down mode. This triggers a hard reset.
            // Section 8.8.2 in the datasheet says the oscillator start-up time is the start up time of the crystal + 37,74μs. Let us be generous: 50ms.
            delay(50);
            hardReset = true;
        }
    }

    if (!hardReset) { // Perform a soft reset if we haven't triggered a hard reset above.
        PCD_Reset();
    }

How can this line work if (digitalRead(_resetPowerDownPin) == LOW) { ? In the MRFC533 documentation, it is stated that NRSTPD pin is Input only so there is no possibility to read anything relevant. I guess that (depending on the microcontroller used) the level can be wrongly read as HIGH.

Will it be possible to change code to something like : in MRFC522.h

void PCD_Reset();
void PCD_HardReset();

in MRFC522.cpp

void MFRC522::PCD_HardReset()
{
    if (_resetPowerDownPin != UNUSED_PIN)
    {
        digitalWrite(_resetPowerDownPin, LOW);  // Make sure we have a clean LOW state.
        delayMicroseconds(2);                   // 8.8.1 Reset timing requirements says about 100ns. Let us be generous: 2μsl
        digitalWrite(_resetPowerDownPin, HIGH); // Exit power down mode. This triggers a hard reset.
        // Section 8.8.2 in the datasheet says the oscillator start-up time is the start up time of the crystal + 37,74μs. Let us be generous: 50ms.
        delay(50);
    }
}

and finally update the PCD_init function by removing the level check on reset pin and calling the new function.

    if (_resetPowerDownPin != UNUSED_PIN)
    {
        pinMode(_resetPowerDownPin, OUTPUT);
        PCD_HardReset();
    }

    else
    { // Perform a soft reset if we haven't triggered a hard reset above.
        PCD_Reset();
    }

I didn't test this code myself now but I will soon ( and i guess others can also greatly improve this code ).

Regards.

Edit: Seems work correctly so far.