Hacking with Claude on a $27 smart watch

The author had a PineTime smart watch lying unused, but a tweet about hacking ESP32 devices with Claude inspired them to try building a custom watch face with AI assistance. They chose the PineTime because it is cheap ($27), runs open-source firmware (InfiniTime or other RTOS), is well-documented, and offers the InfiniSim simulator for a fast feedback loop.

Most of the work was done in OpenCode using open-weight models like Kimi K3 & K2.6 and DeepSeek v4 Pro & Flash rather than Claude itself. The author cloned the InfiniSim repo (with InfiniTime as a git submodule), got a build working on Ubuntu, then asked the model to replicate a Casio-style watch face from a photo, using an existing InfiniTime watch face as a starting point. The AI produced a rough approximation with text sizing and positioning issues, so the author iterated with specific feedback, fixing one element at a time.

To simplify the task, they made the static parts of the screen a fullscreen background image, leaving only the dynamic elements to be coded. This worked in the simulator, and the author was in the process of testing it on a real watch when the narrative cuts off.