Connect SD card to Arduino with or without a level shifter I have some audio files in an SD card and I want to play them using Arduino, thus connect the SD card to the Arduino. Since the transfer of the data will be from the SD card (+3.3V) to the Arduino (+5.0V) and not vice versa, is a level shifter necessary?
You can't use SD card without level conversion from 5 V to 3.3 V. Clock and CS line are driven by the master, and the master must request over MOSI the data to read.