Open-source Codex Micro clone built for $35 by AI scientist

The AgentPad13 project began as a practical desire for a cheaper, open alternative to the $230 Codex Micro, which was also sold out. But it evolved into a test of whether Marvin, an autonomous scientist, could handle a problem far outside its original scope. The key challenge was PCB routing under strict constraints: a 2-layer board (to avoid a 50% price increase for 4-layer) and a 100mm max dimension.

Marvin's approach was to stop treating routers as an oracle and instead synthesize knowledge from literature, datasheets, and working keyboard layouts into a runbook. It then ran iterative experiments, measuring progress against the complete design rather than just the number of unrouted connections. This prevented it from making the same mistakes as previous tools, like breaking USB connectivity to reduce unrouted totals. Key learnings included routing power early and wide, reserving corridors for critical signals, and spreading out the MCU cluster to allow traces to escape.

The final board passed all manufacturing checks and the firmware was simulated before hardware arrived. While the boards work, Marvin made one visible hardware mistake with two underglow LEDs oriented incorrectly, a footprint error that has been fixed. The project also plans to release the routing skill as an open-source package, suggesting the workflow could be reused for other complex design problems.