Schematic

Worked on a schematic this weekend ahead of adding more components to the circuit. I decided to include a buffer to grab the 8-bit address when the Atari executes a STA $D5xx instruction. I figure I can use the 8-bits to add some features or make the protocol simpler.

Excerpt of the schematic showing the Atari 8-bit cartridge edge connector, address and data buses, and decoder logic.

I use the free "maker" version of Autodesk Eagle. Here are the Eagle libraries used in the design:

• Atari 800 parts, including a cartridge board, is at AtariAge. 
• Arduino Nano pinout/footprint on Github. 
• NodeMCU (esp8266 board) pinout/footprint on Github.
• 74xx-eu built-in libary. This library had the HCT logic family where the US version did not. I'm not sure that really matters, but just in case....

I am grateful to the generosity of the individuals and organizations who make the tools and information freely available for hobbyist and maker use. That makes fun hardware projects like this possible.