PSCD32 Development Diary

Interesting circuit board stuff

I found I can get five circuit boards produced for £5.80 from JLCPCB, which doesn't sound at all bad. I've done work on veroboard/stripboard before, but it wasn't very pretty. If I'm going to make this device, I don't want a rickety board to be possibly point of failure. Half-assing things is a good way to destroy everything it's plugged into. Plus, I want it to look super nice. I have no idea how good these boards would be though. China-made... that doesn't really mean much. Good boards, they'll be made in China. Bad boards, they'll be made in China.

I did a wrong

I did a wrong. Here's the PIC24FJ64GA004 family pinout again: And take a look at my Attempt 3 design: The circled pin numbers in my design are the ones that are RPx remappable peripheral pins. I've drawn the PS2 SPI DATA and PS2 SPI COMMAND pins connected to pins 2 and 3 on the PIC, which aren't RPx pins. Oops. I can't use pins 4 or 5 since they're dedicated to the ICSP. I could dual-purpose them, but I'm not entirely confident doing that. I wouldn't want the pad acting strange when the PICkit communicates. In fact, looking back on it now writing this doc, the placements of the other PS2 SPI pins make no sense either. I must've just assumed that they were all RPx pins. I feel a bit of a lemon drawing in the circles afterwards. Aside from that error, I've been a bit more courageous with my resistor values, reducing the safeties and weakening the pull-ups, so the Amiga and MCU have more tug over the lines and more current flows. The maximum input current on any GPIO pin on this PIC is 25mA (Section 27.0), which is bucketloads. A 3-circuit DIP switch on the upper right provides some way to configure the device once it's been built, replacing the jumper from the first design. This is for things like Button to Jump, Autofire, etc. This is why we draw tons and tons of diagrams, and write descriptions of how we expect things to work!