Improve hardware based reset

src/MFRC522.cpp

@@ -204,6 +204,8 @@ void MFRC522::PCD_Init() {
 	
 		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 shure 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);