I have been having a terrible cold for the past 10 days, but I could not be deterred from doing the last testing on the Stage 2 board! The IRQ was a tricky on, mostly because I have forgotten how we designed it to work, and partly to the “weird” design decisions I apparently had made for almost a year ago… There are some slight changes to be made, mostly naming of signals, but apart from that it actually worked as designed.
I will update the github with all the test programs done for stage 2.
And since Stage 2 has almost the same expansion/addon header layout as Stage 3 we can now start developing both video and audio addons, it is just some pins that normally will be unused that have changed to Stage 3. For example have I routed a possibility to have 12v on all 3 headers (if a 12v option board is added, I will post about this later) and that required me to remove address bit AM20 on the video addon socket and moved it on the expansion socket (it was un-used on the audio addon).
Why a 12v option? Well, if I want to make a SID addon for example that will require either 9v or 12v (depending on SID version) and instead of introducing a step-up converter on the audio board (making it more complicated and maybe adding noise) I choose to make it so it is possible to have 12v on the board instead.
So now I will be focusing on testing the PS2 expansion I made for the Stage 1 board to see that the design is valid and working.
