pymata4 VS micro_ros_arduino

The Firmata Protocol provides an abstraction layer for communicating with a microcontroller to read and write its GPIO pins. Currently, it works with Arduino based microcontroller. To use this, you need to install the Firmata firmware on your microcontroller, and then use the client library for sending Firmata commands. The protocol support different client libraries, like Python Pymata4 or other languages like JavaScript and Ruby. There are no ROS abstractions, which means inside the client you would need to write custom code for processing and generating ROS messages.

As far as micro controllers go, it's possible to implement a ROS node on both a raspi pico and arduino that allows them to share data with higher level nodes. That said, these specific implementations are a feature of ROS2. Previously, under the the original ROS, microcontrollers were more treated as 2nd class citizens and relied on a rosserial interface node to communicate with the full network.

I recommend using the Arduino library for Micro-ROS. https://github.com/micro-ROS/micro_ros_arduino

MicroROS is a project to implement a complete ROS2 node in your microcontrollers. The experimental MicroROS Arduino branch extends Arduino programs with additional C/C++ headers for full ROS2 compatible message subscription and publication. Specifically, its provides as precompiled binaries that support specific Microcontrollers such as the Arduino Nano RP2040 Connect or the Teensy 4.1. The list of natively supported ROS messages is impressive.

Hint: You may get some ideas on how everything works from https://github.com/micro-ROS/micro_ros_arduino/blob/foxy/extras/library_generation/library_generation.sh