More updates – things are moving along nicely. All the songs are done now, and any bugs that I can find have been fixed up, so Shredz64 is good to go now. I made an image of the NTSC version of it, I need to make a PAL version as well, but I need to test out the PAL values a little more before thats ready.

Additionally, I uploaded a new version of firmware to the PSX64 that has a couple fixes in it. First, I put the lines out to the C64 into a high impedence state now when they’re not active, which allows you to type on the keyboard when the joystick is plugged on (before it would keep the lines high in a low-impedence state, which would block most keyboard input due to the way the CIAs work). It was irritating as you’d have to unplug the adapter while typing, then plug it back in when it was time to use it. No more of that. Also, I moved the encoding of the lift-up sensor from the pot that handles the strumming to the pot that handles the whammy bar. This allows the user to strum while lifting the guitar up, which wasn’t possible before. This is pretty necessary, as when you activate shred mode, you want to be able to play while the guitar is still lifted up, lest you miss some buttons coming quickly. This is much more important than being able to lift the guitar up while using the whammy bar, especially since the whammy bar is only used in edit mode.

So two things left to do with the next PSX64 prototype – I need to add diodes in on both the DC plug so people can’t plug an adapter with reverse polarity in, and also add diodes to the power on the digital pots. For some reason, it appears that the adapter still works when you don’t have it plugged into DC power. The only power is coming from the C64 5v line (and logic lines). The logic lines go directly into the MCU, so I don’t think that is the issue, but the 5v line goes into the digital pots to drive the pot pins on the C64. I think the digital pots are leaking this power up through their Vdd line into the rest of the circuit, which is bad – most 9 pin joystick ports put out max 50 mA, and the total power consumpution of the interface (and any playstation adapters plugged in) is more than this. If someone accidentally forgot to plug in dc power, it would work fine and they wouldn’t realize it, but there would be a chance of damaging the device/computer. Hopefully by blocking current in the opposite direction of the power pin of the digital pots it will fix this. We’ll see, I have an order in for more playstation extender cables to build another prototype. Once that design checks out, I’ll put the schematics up and get PCBs printed.