title: Arduino with two RC522
body: <p>To pimp up my Carrera I'm going to build a round counter.
  It contains an Arduino Nano, a lcd and 2 rc522 rfid-reader. 
  The readers share the pins for scd, miso, mosi and have own pins for sda and rst.</p>
  
  <p>Actually I'm not able to get the two readers work  together at the same time. Only if the one or the other reader is physically plugged (hardcore!) into the breadbord it works (without code changing). But not together.</p>
  
  <p>It has to be an issue with my code, but where? 
  (The RFID-Communication ist inpired by the example from [addicore][1]<a href="http://www.addicore.com/v/vspfiles/downloadables/Product%20Downloadables/RFID_RC522/RFIDQuickStartGuide.pdf" rel="nofollow">http://www.addicore.com/v/vspfiles/downloadables/Product%20Downloadables/RFID_RC522/RFIDQuickStartGuide.pdf</a>)</p>
  
  <p>Is there anyone who has a hint for me?</p>
  
  <pre><code>    #include &lt;AddicoreRFID.h&gt;
      #include &lt;SPI.h&gt;
      #include &lt;LiquidCrystal.h&gt;
  
      #define uchar unsigned char
      #define uint unsigned int
  
      // create AddicoreRFID object to control the RFID module
      /////////////////////////////////////////////////////////////////////
      //set the pins
      /////////////////////////////////////////////////////////////////////
      //2 - SCK Digital 13
      //3 - MOSI Digital 11
      //4 - MISO Digital 12
  
      const int SS1 = 8; //RFID1
      const int RST1 = 9;
      AddicoreRFID myRFID1 (SS1, RST1);
  
      const int SS2 = 10; //RFID2
      const int RST2 = A0;
      AddicoreRFID myRFID2 (SS2, RST2);
  
      //Maximum length of the array
      #define MAX_LEN 16
  
      //LCD init
      // * LCD RS pin to digital pin 7
      // * LCD Enable pin to digital pin 6
      // * LCD D4 pin to digital pin 5
      // * LCD D5 pin to digital pin 4
      // * LCD D6 pin to digital pin 3
      // * LCD D7 pin to digital pin 2
      LiquidCrystal lcd1(7, 6, 5, 4, 3, 2);
  
      //Counter
      int a = 0;
      int b = 0;
  
      void setup() {
        Serial.begin(9600);
  
        //LCD init
        init_lcd1();
  
        myRFID1.AddicoreRFID_Init();
        myRFID2.AddicoreRFID_Init();
  
      }
  
  
      void loop() {
        uchar i, tmp, checksum1;
        uchar status;
        uchar str1[MAX_LEN];
        uchar str2[MAX_LEN];
  
        ///////////// RFID1 ///////////////////
        // 0x4400 = Mifare_UltraLight -Tag Type
        str1[1] = 0x4400;
        //Find tags, return tag type
        // Manipuliert str1(!);
        //AddicoreRFID::AddicoreRFID_Request(byte reqMode, byte *TagType)
        status = myRFID1.AddicoreRFID_Request(PICC_REQIDL, str1);
        if (status == MI_OK) {
          serial_TagDetect(str1, 1);
        }
        //Anti-collision, return tag serial number 4 bytes
        // Manipuliert str1(!);
        status = myRFID1.AddicoreRFID_Anticoll(str1);
        if (status == MI_OK) {
          serial_TagData(str1);
          lcd_counter(str1, lcd1);
          //delay(500);
        }
        myRFID1.AddicoreRFID_Halt(); //Command tag into hibernation
  
        ///////////// RFID2 ///////////////////
        str2[1] = 0x4400;
        //Find tags, return tag type
        status = myRFID2.AddicoreRFID_Request(PICC_REQIDL, str2);
        if (status == MI_OK) {
          serial_TagDetect(str2, 2);
        }
  
        //Anti-collision, return tag serial number 4 bytes
        status = myRFID2.AddicoreRFID_Anticoll(str1);
        if (status == MI_OK) {
          serial_TagData(str2);
          lcd_counter(str2, lcd1);
          // liest sonst nonstop die Tags!
          //delay(500);
        }
  
        myRFID2.AddicoreRFID_Halt(); //Command tag into hibernation
      }
  
      void init_lcd1() {
         ... inits the lcd ...
      }
  
      // Zählt das Auftreten der Tags
      void lcd_counter (uchar *str, LiquidCrystal lcd ) {
         ... output to the lcd ....
      }
  
      // Meldet gefundenen Tag auf der Konsole
      void serial_TagDetect(uchar *str, int reader) {
          if (reader == 1) {
              Serial.print("RFID1 tag detected: ");
          } else {
              Serial.print("RFID2 tag detected: ");
          }
          Serial.print(str[0], BIN);
          Serial.print(" , ");
          Serial.print(str[1], BIN); Serial.println(" ");
     }
  
    // gibt  Tagdaten auf der Konsole aus
    void serial_TagData(uchar *str) {
        uchar checksum1 = str[0] ^ str[1] ^ str[2] ^ str[3];
        Serial.print("The tag's number is: ");
        //Serial.print(2);
        Serial.print(str[0]);
        Serial.print(" , ");
        Serial.print(str[1], BIN);
        Serial.print(" , ");
        Serial.print(str[2], BIN);
        Serial.print(" , ");
        Serial.print(str[3], BIN);
        Serial.print(" , ");
        Serial.print(str[4], BIN);
        Serial.print(" , ");
        Serial.println(checksum1, BIN);
    }
  </code></pre>
  
  <p>I wonder about that the same(!!) rfid tag has different values depending it gets read from RFID1 or RFID2:</p>
  
  <p>RFID1 tag detected: 1000100 , 0 
  The tag's number is: 136 , 100 , 11100 , 1101011 , 11111011 , 11111011</p>
  
  <p>RFID2 tag detected: 1000100 , 0 
  The tag's number is: 68 , 0 , 0 , 0 , 0 , 1000100</p>