ZONX81plus41 PSG Board with sd-card interface for the ZX-81 now with rev 1.2 firmware on GitHub

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Project PSG board with 32K Ram and SD-card reader
The OS menu, showing files you can download using the SD-card interface.jpeg
Status Initializing
Contact Mahjongg
Last Update 2024-03-26

May 15, 2022 decided to create a ZX-81 compatible version of my PSG board for mt ZX-81 clone the ZX81+38 or a real ZX-81

This is the ZX-81 version of my PSG expansion board for the ZX-81+35 ZX-81 clone

Today I got news that ZX-81 enthusiast Thomas Schilling built my ZX-81+35 and the supporting PSG board, and patched the AY-3-8912 I/O port based sd-card interface to make it work, by adding a few transistors, and then also wrote SD-card drivers based on this interface, and added a menu driven interface so you can load games (.ROM files) from a regular SD-Card. It was a shock that the sd-card interface I had imagined, but had abandoned as impractical could really work, and I saw that with the addition of 32K RAM and 16K of ROM (OTP ROM) this could be a very great expansion board for any ZX-81 (or my own ZX81+38 clone). So I started this new project!

April 5, 2022 Decided on a name for this product

Note that "Zon ZX-81 compatible PSG +32K RAM and SD-Card interface expansion for ZX-81 and clones" is excessively long for a name, so decided on a much shorter name. I decided on ZONX81plus41

I printed out the schematic of the expansion board for the ZX81+35 version at Revspace as a starting point.

I also decided that like competing memory expansion boards, with a PSG option (like the memopak) it should be "plug and play" so it contains an (optional) flash ROM, and 32K static RAM. so a user can just plug it in and it should work without having to open up his ZX-81.

March 20244 T. Schilling released revision 1.2 of his firmware

And I decided to published it on my GitHub pages for the ZX-81plus35 https://github.com/mahjongg2/ZON-compatible-PSG-with-SD-interface-for-ZX81plus35-ZX81 (yes, I decided to keep the shorter name for my ZX-81 version), complete with instructions how to program it in the second 8K of my ZX-81+35 and instructions how to launch the sd-card reader. (by a user call to a easy to remember address 12345. I also published a demo game for it the highness game Dan's revenge. so you have a .ROM file immediately.

So now anyone can get my PSG plus sd-card working as for now only for the ZX81+35.