Okay the title sounds ambiguous because I have yet to find a good way to phrase what I'm looking for.

What I want to accomplish is having a physical cable with an SD card shaped plug on one end, and something such as a USB plug on the other which I can hook into a device and feed SD format data through. I hope that makes sense.

The end goal involves a 3D printer. I have a 3D printer which only reads files from an SD card, but what I want to do is essentially hook up a Pi or such to that SD port and have the 3D printer read from a virtual drive on the Pi.

  • 1
    This question is not Pi specific, but is impossible (without custom hardware) because (except in its lowest SPI compatible mode) the interface uses differential low voltage signalling.
    – Milliways
    Commented Mar 2, 2019 at 6:42
  • 2
    Is there a particular part of the problem you'd like help with? It's far from a simple task but you could start by reading the SD interface specs, to see what you'd need to emulate, both physical and logical. I suspect from the level of detail in the question that a quick read of the specs will put you off, but if you do end up with a specific question perhaps someone will be able to help.
    – Mark Smith
    Commented Mar 2, 2019 at 8:12
  • I was planning on the custom hardware route as a last resort. I was hoping there was already an existing tool somewhere out there for the job. Oh well.
    – Tim Morris
    Commented Mar 2, 2019 at 21:37

2 Answers 2


You could try using a Wifi SD card such as Toshiba Flash Air 16GB Class 10 Wireless Memory Card/Wifi SD Card- that should allow you to drop files onto the card while it's still in the printer. (You have to hope the printer spots the files changing, rather than getting a list of files at the start and working through them. Perhaps it does, perhaps not.)

Failing that, google turned up a few projects relating to emulating SD cards, such as sd card emulation.

  • I looked into Wi-Fi SD cards, but as it turns out (from what I've read), they're a pain in the rear for making data flow in the opposite direction as the manufacturers do not like unintended uses for their products.
    – Tim Morris
    Commented Mar 12, 2019 at 20:02
  • Anyhow, I ended up just hooking up the Raspberry Pi to the 3D printer via USB and using OctoPi -- a far less entertaining, but much simpler solution to my particular problem.
    – Tim Morris
    Commented Mar 12, 2019 at 20:03

For anyone else digging up an answer years later, try the sd card "emulator" (really an sd card switcher, but accomplishes the same goal) here: https://shop.linux-automation.com/usb_sd_mux-D02-R01-V02-C00

(Shipping to your country may or may not be available)

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