I'm trying to connect SD card reader to my Arduino. For testing i'm running CardInfo example.

It seems like it runs ok when I'm running it on my Arduino UNO, but it fails to initialise SD Card while i'm running it on any Arduino with Atmega32U4 chip. I tried on two Leonardo's and Micro Pro.

This is my pinout:

CardReader       Arduino    

CS          <->     4
SCK         <->    13
MISO        <->    12
MOSI        <->    11
VCC         <->    5V 
GND         <->    GND

I'm using Library in version 1.2.1 if that's make difference.

Does anyone have any suggestions?

1 Answer 1


A Leonardo has the SPI pins on the ICSP header, not on pins 11, 12, 13.

Leonardo pinout

And a Pro Micro has the SPI pins on 14, 15, 16.

Pro Micro pinout

  • I remember i used different pins on pro micro, but i really thought i used exactly same on Leonardo and Uno. I bit panicked after suddenly my card stopped working on both boards.
    – user902383
    Feb 20, 2018 at 22:05

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