How to Build a Unified ROS 2 Serial Bridge for Yahboom 520 Motor Drivers

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Developers building 2WD differential drive robots with Yahboom 4-Channel Encoder Motor Driver Boards face a common serial communication conflict when using ROS 2. The Yahboom board uses an onboard STM32F103RCT6 microcontroller to handle encoder reading and PID control, communicating with the host processor via simple UART serial commands. Running separate ROS 2 nodes for odometry and velocity control on the same serial port causes a Linux resource-busy error, since the OS blocks multiple processes from binding to one device simultaneously. The solution is a single unified ROS 2 Python bridge node that holds one shared serial file handle and manages both velocity commands and encoder polling asynchronously at 20Hz. This bridge subscribes to the /cmd_vel topic and publishes odometry data to /odom, sitting cleanly between Nav2 and the physical hardware.

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