Make it useful: storage, controllers and stereo sound

Retrospective build log: 2023-2024 peripheral and software work.

Being able to load and save files makes a homebrew computer much more pleasant to use. I integrated SD/FAT32 work into my firmware and built up a DOS, drawing on George Foot's 6502 SD routines and contributions that added writing support.

Open-source programs were excellent integration tests and good examples to learn from. I added an EB6502 target in my cc65 fork and ported programs including Chess, Gomoku and Breakout. The point was not to claim authorship of those games; it was to understand the runtime and machine-specific work needed to bring them across.

SNES controllers were another satisfying bridge between generations. The pads return digital button states serially, while Apple II software often expects an analog-style joystick interface. The VIA, firmware and soft-switch behavior had to cooperate.

The sound subsystem uses two AY-3-8910s and two 65C22 VIAs in a Mockingboard-style arrangement, giving three tone channels on each side. The AY clocks come from 3RIC's clock, which is not the Apple II's clock; that difference matters to pitch and timing.

The physical disk-emulation subsystem uses a Raspberry Pi Pico. It is a peripheral alongside the real 65C02 and hardware VGA, not a Pico emulating the whole computer.

One video also records an important design change: the 22V10 was replaced with discrete logic. The finished machine is not the earlier GAL prototype.

Storage and software ports:

Controllers and the discrete-logic change:

Disk-emulation demonstrations:

Firmware development: https://github.com/ebadger/msbasic/tree/newboard