I use the extreme burner AVR program you recommended and had no issues with uploading via your QPB to the Saturn adapter. For the PSX one it "seemed" to work as well. Like once it was done flashing the compiled hex the PCB led blinked rapidly for a moment and it also blinks rapidly for a moment when I power on my minigun (personally soldered!
) just like the Saturn one. Except the PS2 controller doesn't register any button presses.
I assume I did something wrong when programming the chip. I picked E2 for the low byte same as the Saturn one. That is the only part I wasn't sure on as I saw the default value 62 also had the internal oscillator at 8Mhz.
PS - you weren't kidding, the 0603 are tiny AF! those are way harder to solder than the 1206 but I managed to get them on.