# Using an old Redmi 9 as the "brain" of a Thymio II: an on-device vision, voice, and obstacle-avoidance learning loop

- Source: Reddit r/robotics
- Published: 2026-10-31T04:01:20.000Z
- RoboHot: https://robohot.news/en/items/cekbo588m8y8zzgrdf3t15tbn
- Original: https://www.reddit.com/r/robotics/comments/1xk0ewg/project_old_redmi_9_as_the_brain_of_a_thymio/

## Summary

A weekend PoC mounts an old Redmi 9 on a Thymio II using Lego, with the phone running ML Kit face detection (including smile probability) and image annotation, rough lighting/motion estimation, animated expressions, and voice output, while the robot only executes wheel-speed targets and sends back sensor data. Behavior is a small state machine: cruise → back up → turn → observe → stop steadily; when a face is detected it enters a "meet" state and can answer "what do you see." Obstacle-avoidance learning is simple: after a collision it tries turning for 1.2s, 2.4s, or 3.8s, scored by the free-driving time before the next contact.