Gleichzeitig mp3 und RFID shield

Hallo,

danke schonmal für die Antworten. Zu den Shields:
Das mp3 shield ist SparkFun MP3 Player Shield - DEV-12660 - SparkFun Electronics
Der RFID reader ist hier: Nr.19 RFID Kit – Funduino – Kits und Anleitungen für Arduino

@amithlon: Genau, der reader ist an 53 angeschlossen. Das mp3shield ist aufgesteckt, wenn ich mir die Pin-Belegung angucke
https://learn.sparkfun.com/tutorials/mp3-player-shield-hookup

würde ich tippen, dass die SD-Karte an pin 9 angeschlossen ist (SD Card CS).
Nachtrag: Die Pin-Belegung ist in einer SPEMP3ShieldConfig.h in der Library gespeichert, hier ein Auszug - bei mir müsste das wie gesagt Pin 9 sein

#if defined(__BIOFEEDBACK_MEGA__)
  #define MP3_XCS             67      //PK5 Output, Active Low,  Control Chip Select Pin (for accessing SPI Control/Status registers)
  #define MP3_XDCS            68      //PK6 Output, Active Low,  Data Chip Select / BSYNC Pin
  #define MP3_DREQ            66      //PK4 Input , Active High, Data Request Pin: Player asks for more data
  #define MP3_RESET           65      //PK3 Output, Active Low,  Reset is active low
  #define SD_SEL              76      //PJ6 Output, Active Low
  #define MP3_DREQINT          5 //Corresponding INTx for DREQ pin
#elif ( SEEEDUINO == 1 ) // if SEEDUINO use the following pin outs
  #define MP3_XCS             A3 //Control Chip Select Pin (for accessing SPI Control/Status registers)
  #define MP3_XDCS            A2 //Data Chip Select / BSYNC Pin
  #define MP3_DREQ            A1 //Data Request Pin: Player asks for more data
  //#define MP3_DREQINT        0 // There is no IRQ used on Seeduino
  #define MP3_RESET           A0 //Reset is active low
  #define SD_SEL              10 //select pin for SD card
#elif ( TEENSY2 == 1 )
  #define MP3_XCS              7
  #define MP3_XDCS             8
  #define MP3_DREQ             4
  #define MP3_DREQINT          1
  #define MP3_RESET            9
  #define SD_SEL               0 // Teensy SDI CS on pin 0
  // Connect SDI pins as follows:
  // Sparkfun shield 11 -> Teensy 2 (mosi)
  // Sparkfun shield 12 -> Teensy 3 (miso)
  // Sparkfun shield 13 -> Teensy 1 (sck)
// if BARETOUCH or ARDUINO_AVR_BARETOUCH use the following pin map
#elif (( BARETOUCH == 1 ) || ( ARDUINO_AVR_BARETOUCH == 1 )) 	
  #define MP3_XCS             9  //Control Chip Select Pin (for accessing SPI Control/Status registers)
  #define MP3_XDCS            6  //Data Chip Select / BSYNC Pin
  #define MP3_DREQ            7  //Data Request Pin: Player asks for more data
  #define MP3_DREQINT         4  //Corresponding INTx for DREQ pin
  #define MP3_RESET           8  //Reset is active low
  #define SD_SEL              5  //select pin for SD card	
// otherwise use pinout of typical Sparkfun MP3 Player Shield.
#else // otherwise use pinout of typical Sparkfun MP3 Player Shield.
  #define MP3_XCS              6 //Control Chip Select Pin (for accessing SPI Control/Status registers)
  #define MP3_XDCS             7 //Data Chip Select / BSYNC Pin
  #define MP3_DREQ             2 //Data Request Pin: Player asks for more data
  #if defined(__AVR_ATmega32U4__)
    #define MP3_DREQINT          1 //Corresponding INTx for DREQ pin
  #else // swapped between Uno and Leonardo.
    #define MP3_DREQINT          0 //Corresponding INTx for DREQ pin
  #endif
  #define MP3_RESET            8 //Reset is active low
  #if ( GRAVITECH == 1 )
    #define SD_SEL               4 //select pin for SD card
  #else
    #define SD_SEL               9 //select pin for SD card
  #endif // GRAVITECH
#endif // none SEEEDUINO