Support Micro SD card, Micro SDHC card (high speed card)
board level conversion circuit, namely the interface level for 5V or 3.3V
The communication interface is a standard SPI interface
Level conversion circuit: Micro SD card to signal the direction of converts 3.3V, MicroSD card interface to control the direction of the MISO signal is also converted to 3.3V, general AVR microcontroller systems can read the signal