Better implementation of the PCD_Init() method. Thanks to Rotzbua

to point this out.

MFRC522.cpp

@@ -14,7 +14,6 @@
  * Constructor.
  */
 MFRC522::MFRC522() {
-  
 } // End constructor
 
 /**
@@ -45,7 +44,7 @@ void MFRC522::setSPIConfig() {
  * Writes a byte to the specified register in the MFRC522 chip.
  * The interface is described in the datasheet section 8.1.2.
  */
-void MFRC522::PCD_WriteRegister(byte reg,		///< The register to write to. One of the PCD_Register enums.
+void MFRC522::PCD_WriteRegister(	byte reg,		///< The register to write to. One of the PCD_Register enums.
 									byte value		///< The value to write.
 								) {
 	digitalWrite(_chipSelectPin, LOW);		// Select slave
@@ -58,7 +57,7 @@ void MFRC522::PCD_WriteRegister(byte reg,		///< The register to write to. One of
  * Writes a number of bytes to the specified register in the MFRC522 chip.
  * The interface is described in the datasheet section 8.1.2.
  */
-void MFRC522::PCD_WriteRegister(byte reg,		///< The register to write to. One of the PCD_Register enums.
+void MFRC522::PCD_WriteRegister(	byte reg,		///< The register to write to. One of the PCD_Register enums.
 									byte count,		///< The number of bytes to write to the register
 									byte *values	///< The values to write. Byte array.
 								) {
@@ -225,43 +224,15 @@ void MFRC522::PCD_Init() {
 /**
  * Initializes the MFRC522 chip.
  */
-void MFRC522::PCD_Init(byte chipSelectPin, byte resetPowerDownPin) {
+void MFRC522::PCD_Init(	byte chipSelectPin,		///< Arduino pin connected to MFRC522's SPI slave select input (Pin 24, NSS, active low)
+		        byte resetPowerDownPin	///< Arduino pin connected to MFRC522's reset and power down input (Pin 6, NRSTPD, active low)
+		      ) {
 	_chipSelectPin = chipSelectPin;
 	_resetPowerDownPin = resetPowerDownPin; 
-	
 	// Set the chipSelectPin as digital output, do not select the slave yet
-	pinMode(_chipSelectPin, OUTPUT);
+	PCD_Init();
-	digitalWrite(_chipSelectPin, HIGH);
-
-	// Set the resetPowerDownPin as digital output, do not reset or power down.
-	pinMode(_resetPowerDownPin, OUTPUT);
-
-	// Set SPI bus to work with MFRC522 chip.
-	setSPIConfig();
-
-	if (digitalRead(_resetPowerDownPin) == LOW) {	//The MFRC522 chip is in power down mode.
-		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 + 37,74<37>s. Let us be generous: 50ms.
-		delay(50);
-	}
-	else { // Perform a soft reset
-		PCD_Reset();
-	}
-	
-	// When communicating with a PICC we need a timeout if something goes wrong.
-	// f_timer = 13.56 MHz / (2*TPreScaler+1) where TPreScaler = [TPrescaler_Hi:TPrescaler_Lo].
-	// TPrescaler_Hi are the four low bits in TModeReg. TPrescaler_Lo is TPrescalerReg.
-	PCD_WriteRegister(TModeReg, 0x80);			// TAuto=1; timer starts automatically at the end of the transmission in all communication modes at all speeds
-	PCD_WriteRegister(TPrescalerReg, 0xA9);		// TPreScaler = TModeReg[3..0]:TPrescalerReg, ie 0x0A9 = 169 => f_timer=40kHz, ie a timer period of 25<32>s.
-	PCD_WriteRegister(TReloadRegH, 0x03);		// Reload timer with 0x3E8 = 1000, ie 25ms before timeout.
-	PCD_WriteRegister(TReloadRegL, 0xE8);
-	
-	PCD_WriteRegister(TxASKReg, 0x40);		// Default 0x00. Force a 100 % ASK modulation independent of the ModGsPReg register setting
-	PCD_WriteRegister(ModeReg, 0x3D);		// Default 0x3F. Set the preset value for the CRC coprocessor for the CalcCRC command to 0x6363 (ISO 14443-3 part 6.2.4)
-	PCD_AntennaOn();						// Enable the antenna driver pins TX1 and TX2 (they were disabled by the reset)
 } // End PCD_Init()
 
-
 /**
  * Performs a soft reset on the MFRC522 chip and waits for it to be ready again.
  */
@@ -406,7 +377,7 @@ bool MFRC522::PCD_PerformSelfTest() {
  * 
  * @return STATUS_OK on success, STATUS_??? otherwise.
  */
-byte MFRC522::PCD_TransceiveData(byte *sendData,		///< Pointer to the data to transfer to the FIFO.
+byte MFRC522::PCD_TransceiveData(	byte *sendData,		///< Pointer to the data to transfer to the FIFO.
 									byte sendLen,		///< Number of bytes to transfer to the FIFO.
 									byte *backData,		///< NULL or pointer to buffer if data should be read back after executing the command.
 									byte *backLen,		///< In: Max number of bytes to write to *backData. Out: The number of bytes returned.
@@ -1221,7 +1192,10 @@ byte MFRC522::PICC_GetType(byte sak		///< The SAK byte returned from PICC_Select
 	if (sak & 0x04) { // UID not complete
 		return PICC_TYPE_NOT_COMPLETE;
 	}
-	
+	//http://www.nxp.com/documents/application_note/AN10833.pdf 
+	//3.2 Coding of Select Acknowledge (SAK)
+	//ignore 8-bit
+	sak&=0x7F;
 	switch (sak) {
 		case 0x09:	return PICC_TYPE_MIFARE_MINI;	break;
 		case 0x08:	return PICC_TYPE_MIFARE_1K;		break;

MFRC522.h

@@ -339,7 +339,7 @@ public:
 	// Functions for manipulating the MFRC522
 	/////////////////////////////////////////////////////////////////////////////////////
 	void PCD_Init();
-	void PCD_Init(byte, byte);
+	void PCD_Init(byte chipSelectPin, byte resetPowerDownPin);
 	void PCD_Reset();
 	void PCD_AntennaOn();
 	void PCD_AntennaOff();

examples/ReadUidMultiReader/ReadUidMultiReader.ino

@@ -10,6 +10,9 @@
  * This sample shows how to read and write data blocks on a MIFARE Classic PICC
  * (= card/tag).
  *
+ * BEWARE: Data will be written to the PICC, in sector #1 (blocks #4 to #7).
+ *
+ *
  * Typical pin layout used:
  * -----------------------------------------------------------------------------------------
  *             MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
@@ -17,7 +20,7 @@
  * Signal      Pin          Pin           Pin       Pin        Pin              Pin
  * -----------------------------------------------------------------------------------------
  * RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
- * SPI SS 1    SDA(SS)      5             53        D10        10               10
+ * SPI SS 1    SDA(SS)      10            53        D10        10               10
  * SPI SS 2    SDA(SS)      2             53        D10        10               10
  * SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
  * SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
@@ -28,9 +31,9 @@
 #include <SPI.h>
 #include <MFRC522.h>
 
-#define RST_PIN         9           // Configurable, see typical pin layout above
+#define RST_PIN        10           // Configurable, see typical pin layout above
 #define SS_1_PIN        5          // Configurable, see typical pin layout above
-#define SS_2_PIN        2          // Configurable, see typical pin layout above
+#define SS_2_PIN        3          // Configurable, see typical pin layout above
 
 #define NR_OF_READERS   2
 
@@ -38,12 +41,11 @@ byte ssPins[] = {SS_1_PIN, SS_2_PIN};
 
 MFRC522 mfrc522[NR_OF_READERS];   // Create MFRC522 instance.
 
-MFRC522::MIFARE_Key key;
-
 /**
  * Initialize.
  */
 void setup() {
+
   Serial.begin(115200); // Initialize serial communications with the PC
   while (!Serial);    // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
 
@@ -61,10 +63,12 @@ void loop() {
 
     for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
     // Look for new cards
-    if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
 
+    if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
+      Serial.print(F("Reader: "));
+      Serial.print(reader);
       // Show some details of the PICC (that is: the tag/card)
-      Serial.print(F("Card UID:"));
+      Serial.print(F(" Card UID:"));
       dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
       Serial.println();
       Serial.print(F("PICC type: "));