Image: reddit.com · Video still: Plug an ESP32-S3 into an Android phone. The phone becomes the 'Cardputer'
An Android phone as the screen and keyboard for Cardputer apps
Patched libraries let Cardputer apps run on a bare ESP32-S3 plugged into an Android phone, which shows the screen and sends key presses; built with Claude Code.
Credits
- Reddit poster Feisty-Sky-6018 Source ↗
Earliest dated source:
The full story
The maker patched the M5GFX display library and the M5Cardputer keyboard library so that every pixel write is sent out over the ESP32-S3's USB port and key presses can arrive from it. An app rebuilt against the patched libraries runs unchanged on a bare ESP32-S3 devkit plugged into an Android phone by OTG, with the phone acting as screen and keyboard.
Because stock binaries are statically linked, the Android app has them rebuilt: a small proxy triggers a GitHub Actions job that clones any open-source Cardputer app, swaps in the patched libraries and compiles it with PlatformIO, which takes about two minutes warm, and the phone then flashes the board. The post credits Claude Code with the writing ("I (claude code) wrote").
How it was done
Tools
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Sources
From a short post by the maker, so the details are as they tell them.
- Reddit: Plug an ESP32-S3 into an Android phone. The phone becomes the 'Cardputer'Reddit poster: Feisty-Sky-6018Posted
The maker's post on r/esp32.
If it disappears: archived copy of Reddit: Plug an ESP32-S3 into an Android phone. The phone becomes the 'Cardputer' (opens in a new tab)