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Project 003 · Working subsystem

DJI O4 automated test-bench control

A Raspberry Pi Pico based controller used to make DJI O4 laboratory tests repeatable: controlled power, FC-style serial communication, arming state and evidence-friendly test sequences.

Scope. This page documents the test-bench controller rather than RF protocol reverse engineering. Tests are performed as controlled, low-power bench experiments.

The problem

RF experiments are much easier to compare when the transmitter starts from a known state every time. Manually powering, arming and configuring a test unit introduces variation and makes longer automated test sequences difficult to reproduce.

Architecture

O4 TEST-BENCH CONTROL
Linux / Labrax
↓
Raspberry Pi Pico
↓
Power relay / cutoff
FC-style serial control
↘    controlled test state    ↙
DJI O4 test unit

Confirmed on the bench

ControllerDedicated Raspberry Pi Pico
Serial linkUART, 115200 8N1
Control modelFC-style MSPv1 messaging
SafetyIndependent hardware power cutoff

The controller can reproduce arming/disarming behaviour used by the test setup and provides a deterministic way to bring the O4 unit into a known bench state. The setup also demonstrated voltage telemetry in the goggles and a working DisplayPort OSD path used during development.

Why the hardware cutoff matters

Software automation should not be the only mechanism capable of ending a transmitter test. The bench therefore includes an independent relay cutoff with a verified time limit. Test orchestration is designed around bounded runs and cooldown periods rather than indefinite transmission.

What this enables

With power and control under software supervision, a Linux host can run repeatable experiments, associate captures with known transmitter state and retain evidence from each test. This is more useful for Sky Serpent development than manually operating the transmitter for every capture.

Confirmed functionality is published here; implementation details that would expose unrelated RF reverse-engineering work remain outside the public article.