So one of my latest excessive uses of claude is a remake of my msx-rom-and-floppy-emulator but using a RP2350B board. Like a lot of nerdy types I bought a Raspberry Pi pico 2 when it came out years ago thinking I could do clever rom emulation stuff with it, but I kept on having issues and gave up on it. Of course there’s been some issues/errata with the earlier versions of the RP2350 chip and I just blamed those 😉 More recently I was reading how the A4 stepping of the chip solves most issues and is almost 5V tolerant on most of its GPIO pins … and thats good enough for me.

The RP2350B is the bigger version with 48 GPIO pins. I bought the Weact RP2350B board off aliexpress. The 0 to 39 pins are the mostly 5V tolerant ones and the 40 to 47 ones are still 3V3. Anyway, that is enough IO’s to attempt to do some of the stuff I’ve been doing with the STM32F4 chips.

As this was yet another AI experiment for me, I got claude to reference the RPROM project (RP2350B emulating an Amiga kickstart rom) and my own v9938 branch of the Apple II VGA stuff as I wanted to have another go at trying to do VGA output at the same time that the ROM and floppy emulation is underway. As a general overview of using claude to build this, it was very good, but there were several times I had to just stop and dig through the code to work out what it was doing. In quite a few cases it just kept taking (to me) the wrong approach. This very ‘time sensitive’ coding is an unusual branch of the art, but claude is actually quite good at counting cycles and figuring things out … but often it stabs itself in the foot with some of the changes it tries.

So I was worried about claude writing something that would actively blow up my precious vintage computers, so I used my MSX breadboard computer as a starting point, and as it got to a more workable state, I ported it to work on the Omega MSX2. Moving it to the Omega was a good example of claude overdoing it. It was working fine on the breadboard MSX, and the changes to get it working on the Omega are mostly around having a real _SLTSL signal … and of course it sutffs it up entirely. I was hoping for a minor defensive change and it goes and changes heaps of stuff …. which didn’t work. I get it to rewind and try to do the smallest change … and of course it then works. I feel like a manager and a tester at times with AI 😉

Anyway, it all works pretty well. Just like with the msx-rom-and-floppy-emulator it didn’t work on the FS-A1 since _SLTSL arrives very late on that system. But I soon got that fixed. The V9938 emulation I worked on a while back, now works much better. Where I had minor graphical errors in games like Fray, it all seems to work perfectly. Treasure of Usas works fine. Metal Gear and King Kong 2 seem to be OK too. Note, the photos show my GBS-8200, but its not being used. The RP2350B is direct to the VGA of the monitor.

Source is at https://github.com/kernelcrash/rp-msx-rom-and-floppy-emulator