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A project log for OpenSpand ZX81 expansion

OpenSpand is a ZX81 expansion cartridge based on an RP2350B chip. Like a ZXpand+ with extended functionality.

adamklotblixtadam.klotblixt 12/17/2024 at 15:580 Comments

After some beep-testing, ocular verification and soldering the only fault I found was a mirrored pinout for the USB module. No problem, just mounted it upside down.

Software testing showed that the new joystick and soft-reset/config button reading worked as expected. Nice, hadn't really tested it before!

The only major fault I found was that the micro-SD module I used had a different pinout compared to the datasheet I used. 3 patch wires solved that. Not very good looking but serviceable.

Next up is trimming the LED resistors to give enough light. The LEDs come from my old stash, so I had no datasheet for them and will have to test my way to a decent current.

The PCB was fault free and I had no problem soldering everything. All faults were my own. I'll fix all the faults, make some improvements and make a final version later. Now it's time to work on the software and think hard on all the possible hardware improvements.

I certainly won't hesitate ordering from PCBX.com again, it all went as smoothly as hoped.

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