Add a Second SD Card to the Pi Zero

The Raspberry Pi Zero is a beautiful piece of hardware, fitting an entire Linux computer into a package the size of a pack of gum (don’t chew it, though). However, this size comes with limited IO options, which can be a complication for some projects. In this case, [Hugatry] wanted extra storage, and devised a smart method to add a second SD card to the Pi Zero.

The problem with the Pi Zero is that with only a single USB port, it’s difficult to add any other storage to the device without making things bulkier with hubs or other work arounds. Additionally, the main SD card can’t be removed while the Pi is running, so it makes sense to add an easy-to-use removable storage option to the Pi Zero.

It’s quite a simple hack – all that’s required to pull it off is a few resistors, an SD card connector, and some jumper wires. With everything hooked up, a small configuration change enables the operating system to recognise the new card.

Overall it’s great to see hacks that add further functionality to an already great platform. If you find it’s not powerful enough, you can always try overclocking one. 

19 thoughts on “Add a Second SD Card to the Pi Zero

    1. It has been done before actually. http://ralimtek.com/Raspberry_Pi_Secondary_SD_Card/

      It took years for somebody to try because it uses the second SD controller in the Broadocm SoC which was undocumented and isn’t anything like the main Arasan SDHCI controller used for the SD card. Broadcom only wrote the SDIO driver for it at the end of 2015 because the RPi 3 uses the same controller for the onboard WiFi/Bluetooth interface. The RPi Zero uses the same interface and wireless chip.

        1. Oops. I missed the W off my original post. Nope. You can’t use this on a RPi 3 or RPi Zero W if you still want the onboard WiFi. If you don’t need the onboard WiFi then you should be able to map the SD controller to the GPIO header for the SD card.

          1. In damn Russia? :( Let the Russian Post and the customs die in a big fire. Either no one wants to ship here, or shipping costs more than the hardware itself.

          2. Yeah, but why are suppliers still limiting customers to only 1? The shipping more than doubles the cost. Instead of churning our supposedly incrementally better models, why not just build more of the existing models?

  1. What about using a single chip SD reader solution?
    I had to order 5 of these because the card reader on my C650D is b0rked and won’t work properly.
    Connector isn’t the problem but it knocks out Vcc for the card when the chip goes all lumpy.

    Pretty sure the Pi can handle the IO requirements as the chip needs maybe 4 lines max.
    For added hacking potential run it off the unused clock output from the video out header which is IIRC synced to the Pi’s
    internal 19.2MHz crystal.

  2. “Additionally, the main SD card can’t be removed while the Pi is running” Not true, there are examples of people moving the running OS into RAM or USB storage and being able to remove the SD.

  3. >>However, this size comes with limited IO options, which can be a complication for some projects
    What do you mean? It has the full 40 pin header the other modern Raspberry Pi boards do.

    1. Which is my complaint about the Pi. Too little I/o. All that computing power with limited ways to get data in and out.
      That and the *$%@ing micro usb power connector.

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