I decided that rather than attempt to replace the soundbox, I would initially do a replacement for the NeXT keyboard and mouse combination. This is partly because the NeXT monitor bus appears to operate at around 20MHz making it that much harder to reverse engineer, and partly because I wanted to get back into practice programing MCUs (it has been a while). So, I broke out my box of PIC processors… for this, I’m attempting to use the PIC16F88, but there are options like the PIC18, PIC24 and PIC32 that are quite appealing for different reasons, not the least of which is USB support. …

I have been developing a replacement for the NeXT monitor and/or soundboard for a while now because the monochrome systems rely on an N4000, N4000A, or N4000B monitor. You can get around the issue by having a non-ADB soundbox and building a video converter, but the non-ADB soundboxes are hard to find too, and older models can’t use ADB versions… and even if they could, the ADB systems weren’t fully compatible with a lot of the NeXT software. …