Adafruit MicroSD SPI or SDIO Card Breakout Board

Convenient project storage (since there's still no breakout board for floppy disks)

by Jeff Epler

published July 31, 2020, last edited September 17, 2025

posted in Adafruit Products CircuitPython Breakout Boards/ Storage

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Beginner

Product guide

Feather STM32F405 Express

sdioio uses SDIO high-speed interface to communicate with SD cards, it is not pin compatible with SPI and requires special wiring. Not all chips support SDIO, and if they do, you usually have to use special pins! It also requires CircuitPython 6.0.

The Feather STM32F405 Express uses SDIO to connect its built in micro SD card slot. Didn't notice it had an SD card slot? We hid it on the underside.

To mount the SD card, use the following code. Remember to put it in the file mount_sd.py on CIRCUITPY so you can easily call it from code.py or the REPL with import mount_sd.

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import board
import sdioio
import storage

sdcard = sdioio.SDCard(
    clock=board.SDIO_CLOCK,
    command=board.SDIO_COMMAND,
    # Note that board.SDIO_DATA is a tuple of four pins, not a single pin.
    data=board.SDIO_DATA,
    frequency=25000000)

vfs = storage.VfsFat(sdcard)

storage.mount(vfs, "/sd")

import board
import sdioio
import storage

sdcard = sdioio.SDCard(
    clock=board.SDIO_CLOCK,
    command=board.SDIO_COMMAND,
    # Note that board.SDIO_DATA is a tuple of four pins, not a single pin.
    data=board.SDIO_DATA,
    frequency=25000000)

vfs = storage.VfsFat(sdcard)

storage.mount(vfs, "/sd")