Open AC-1's Core Is an Apple I Surrounded by VGA, USB Keyboard, and SD Card Features
Iconic computer reimagined with a combination of the 6502, Arduino Nano, and PIC32.
The Apple I was an influential step in personal computing history. Clones of it have grown in popularity since real machines are rare (and expensive.) Instead of creating yet another clone, retro computer enthusiast Chris Davis took a different approach. The Open AC-1 is a reimagined Apple I with a 6502 at its core and modern microcontrollers supporting it.
The Open AC-1 circuit board contains RAM, ROM, a Peripheral Interface Adapter, glue logic, and several microprocessors. A Western Design Center (WDC) 65c02 runs the eight-bit Wozrom and BASIC code. Modern interfaces are available via a Microchip PIC32 and an Arduino Nano.
The PIC32 has two tasks: USB keyboard input and VGA video output. It communicates with an Arduino Nano. The Nano connects to the 65c02's data bus via an MCP23517 I/O Expander. The Arduino also provides an interface to an SD card.
Unlike the original Apple I, BASIC is available in ROM. Which means the computer is ready to use after it boots. You can load BASIC programs from the SD card. The ROM also contains Wozmon, which is a monitor program. In older computers, the monitor allows you to view or change memory contents. Some even allowed for assembling and dissembling short programs.
In some ways, this kit is reminiscent of the RetroShield. The project used a real 6502 (or Z80) processor connected to an Arduino Mega emulating vintage computers' logic. The Open AC-1, however, better reassembles the original Apple I with its handful of ICs cleanly laid out on a printed circuit board.
Overall, the Open AC-1 does a fantastic job of augmenting vintage technologies with modern components. Davis designed the kit entirely with through-hole components, which should make soldering more accessible to those new to soldering.
Davis says the project is fully open source, even though the GitHub repository (currently) lacks design files beyond a PDF of the schematic. Even though you can buy the Open AC-1 as an assembled kit, the assembly and operations manual does contain significant documentation.
A fully assembled Open AC-1 is available for $129 before shipping.
Electronics enthusiast, Bald Engineer, AddOhms on YouTube and KN6FGY.