SparkFun SD/MMC Card Breakout

With SD and MMC memory prices dropping, the time is right for mass storage and datalogging. This breakout board will allow you to breakout the SD/MMC socket to a standard .1" 10-pin header. Perfect for breadboarding and the likes. Board comes fully assembled and tested as shown.

  • 1.3" x 1.5"

SparkFun SD/MMC Card Breakout Product Help and Resources

MicroSD Shield and SD Breakout Hookup Guide

March 25, 2015

Adding external storage in the form of an SD or microSD card can be a great addition to any project. Learn how in this hookup guide for the microSD shield and SD breakout boards.

Logic Levels and Connections

You must bring the voltage down from a 5V Arduino with a logic level converter. If you don't have a logic level converter, you can use some resistors like the ones that were used in our old logic level converter To use with Arduino, there is an SD card library that has already been written =>

Note: In relation to the SD Mode and the pins of this breakout:

- CS/SS should be connected to CD/DAT3, which is labeled as D3
- MISO should be connected to DAT0 which is labeled D0
- MOSI should be connected to CMD which is labeled as CMD on the board

We also have a tutorial using the microSD Shield that might be of some use => Try looking at the design of the microSD shield to connect to an Arduino Uno footprint. There are other widgets on our storefront that use the microSD (like the OpenLog or LilyPad MP3 to name a few). Try looking at the Eagle board layouts and schematics for an idea of how to connect a microcontroller to the SD and microSD cards.

Core Skill: Soldering

This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.

1 Soldering

Skill Level: Noob - Some basic soldering is required, but it is limited to a just a few pins, basic through-hole soldering, and couple (if any) polarized components. A basic soldering iron is all you should need.
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Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • DaddyOh / about 10 years ago / 3

    It is late and I am very tired. If this is obvious I'm not getting it. For the life of me I can't decipher the pin out to sd card / spi on the breakout. From the upper left (card goes in in the right) they are labeled


    I want to hook this up to a spi bus device (mbed) and I get the VCC, GND, CLK but which ones are:

    SPI mosi SPI miso CS

  • Member #602203 / about 10 years ago / 2

    We are also struggling finding the CS, like DaddyOh has reported :/

    Please help

  • IgnacioV / about 10 years ago / 2

    Mounting holes are always good.

  • Member #635091 / about 9 years ago / 1

    I would like a sanity check on my circuit as I have not gotten this sd card reader to work. I have wired it as such using pull down resistors to bring I/O and power down to 3.3V and am using the following code with the pin changed to pin 10 , yet I still get SD library initialization failed. Anyone have any suggestions?

  • 8r13n / about 10 years ago / 1

    Do I need to add anything to this or can I wire it directly to my microprocessor board? I know normally there are some pull up/down resistors.

    • Summit783 / about 10 years ago / 1

      Yeah you may need some resistors on the SPI lines actually. I would recommend "SD Card Projects Using the PIC Microcontroller" by Dogan Ibrahim. He walks you through a variety of different projects, near the end he has a data logging project. Even if you're not using a PIC, it may still be worth a look so that you know what to be cognizant of with your circuit.

      • 8r13n / about 10 years ago * / 1

        Does it make a difference if I'm using an STM32F4 to drive it? I won't bit bang, I'll be using the SDIO hardware feature of the chip? I have internal resistors, they're not strong enough?

        I've been working with SD cards for a long time now using this chip. But they've always been on the same board.

        • Summit783 / about 10 years ago / 1

          I'm not sure about the STM32F4, as long as it has some type of SPI module, you should be fine.

          But internal resistors will not be strong enough, here's a promising webpage I found about SD cards and PIC projects. Even if you're using a diff mcu (microcontroller) the main takeaways are the same (1) use a library to comm with the SD card and (2) have some resistors on the lines from your mcu to the SD card. This is the link:

          • 8r13n / about 10 years ago / 1

            I'll try it and report back. That link seemed to say they needed the resistors because their IO logic pins were ~4v. Stm32 is 3.3v :)

            • 8r13n / about 9 years ago / 1

              STM32F4 needed the resistors, but it works great! I'm driving it with a Cerb40 II board from GHI.

    • IgnacioV / about 10 years ago / 1

      It's just the bare socket. All the interface stuff is your problem.

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This works fine for a barebones board

but I wish the board included pullup resistors, which are recommended for all SD/MMC card circuits.