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SDBox: a cheap SD card adapter for your Amiga     (posted 2023-08-21)

I was watching the videos on the BBC Master computer on the Adrian's Digital Basement Youtube channel. Adrian has cleaned up this old Acorn BBC Master, restored the keyboard to full functionality and then started to "Americanize" it by changing the power supply to use 120 V, and making the composite video NTSC rather PAL.

But what really peaked my interest is that he made a tiny little interface to hook up SD cards to the Master's user port. I think it only uses four wires. There's a very small circuit board, but that only has some resistors to adapt the user port's 5 V to the 3.3 V used by SD cards. Apparently, that's all the hardware you need for reading (and writing?) SD cards. Wow.

Digging a bit deeper, it looks like SD cards use the super simple Serial Peripheral Interface (SPI) interface/protocol as a lowest common denominator. And that is a protocol that you can bit bang with a few general purpose IO lines without trouble. That's going to be slow, but it'll still work.


Could this also work on an Amiga?

One of the issues with Amigas is that none of their I/O options are in general use today. Getting data on and off your Amiga can be a challenge, especially for A500s without any additional hardware. So a simple way to read and perhaps write SD cards would be very welcome. Turns out, there are indeed cheap/easy solutions to use SPI in general or use SD cards with through the printer port on all Amigas (except for the A1000).

If you are inclined to build your own hardware, have a look at the SDBox-v2 github repository. You can also buy one premade for about 50 euros. And read this review to learn how well it works.

It does use an Arduino to translate the parallel I/O from the Amiga's printer port to SPI on the SD card side, though, no bit banging.

I'd say that with an A600 or A1200 you're better off with CF cards in the PCMCIA slot for about the same price, or perhaps a PCMCIA card network card with a driver off of Aminet.

I'd say that for an A500 or an A2000 without a harddrive, a Gotek floppy emulator is probably a better option. But for any non-A600/A1200 without a harddrive, the SDBox is a great solution because it lets you files that are larger than what fits on one floppy on your computer.

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