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Built an autonomous AprilTag chaser on a PiCar-X — v1 in action
Been working on a PiCar-X build on a Raspberry Pi 4B. v1 goal: detect an AprilTag (36h11 family, ID 0), steer toward it with a PID controller, drive forward, and stop at a configured distance threshold. Toggle it on from a browser dashboard, 3-second countdown, and it goes. I built this entirely with Claude Code. It’s been a massive productivity boost while balancing a full-time job, and the process of building agentically has been a great learning experience. WebSocket concurrent send corruption The broadcast coroutine and the sensor push loop were both calling send_json() concurrently. At await boundaries they interleaved, Starlette threw, and the client was silently dropped from the send set — meaning the toggle-off confirmation never arrived and the button stayed stuck in active state even after the car stopped. Fixed by replacing the shared client set with a per-connection asyncio.Queue and a single drain task per connection. Camera color inversion that didn't respond to the obvious fixes BGR888 didn't fix it. RGB888 + cvtColor didn't fix it either. Root cause: capture_array() on this Pi hardware returns RGB regardless of the format name, and this platform's libjpeg encodes from RGB input correctly without any conversion. One-line fix once the actual data layout was confirmed via a frame diagnostic log. Had to fully remove Vilib It uses a Picamera2 internal API (allocator) removed in 0.3.36 — crashes on any camera restart after a chase session. Server now owns Picamera2 directly for the full session lifetime. What's next v2 candidates on the list: distance-proportional speed, latching stop behavior, camera tilt tracking, and operator override during chase. Stack: Raspberry Pi 4B · PiCar-X v2.0 · Picamera2 · pupil-apriltags · FastAPI · Python 3.13 submitted by /u/okineedaplan [link] [Kommentare] reddit.com · reddit.com
Been working on a PiCar-X build on a Raspberry Pi 4B. v1 goal: detect an AprilTag (36h11 family, ID 0), steer toward it with a PID controller, drive forward, and stop at a configured distance threshold. Toggle it on from a browser dashboard, 3-second countdown, and it goes. I built this entirely with Claude Code. It’s been a massive productivity boost while balancing a full-time job, and the process of building agentically has been a great learning experience. WebSocket concurrent send corruption The broadcast coroutine and the sensor push loop were both calling send_json() concurrently. At await boundaries they interleaved, Starlette threw, and the client was silently dropped from the send set — meaning the toggle-off confirmation never arrived and the button stayed stuck in active state even after the car stopped. Fixed by replacing the shared client set with a per-connection asyncio.Queue and a single drain task per connection. Camera color inversion that didn't respond to the obvious fixes BGR888 didn't fix it. RGB888 + cvtColor didn't fix it either. Root cause: capture_array() on this Pi hardware returns RGB regardless of the format name, and this platform's libjpeg encodes from RGB input correctly without any conversion. One-line fix once the actual data layout was confirmed via a frame diagnostic log. Had to fully remove Vilib It uses a Picamera2 internal API (allocator) removed in 0.3.36 — crashes on any camera restart after a chase session. Server now owns Picamera2 directly for the full session lifetime. What's next v2 candidates on the list: distance-proportional speed, latching stop behavior, camera tilt tracking, and operator override during chase. Stack: Raspberry Pi 4B · PiCar-X v2.0 · Picamera2 · pupil-apriltags · FastAPI · Python 3.13 submitted by /u/okineedaplan [link] [Kommentare]
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