Blink LED Example on an ESP32 Using MicroPython and ROS2
hadabot.com
hadabot.com
So I am guessing that it is a firmware system preloaded and running on microcontrollers built into robot hardware that your own code, running on your microcontroller, sends commands to, and collects reports from.
Achieving a blinking LED is a good start for working out the mechanics of getting code compiled, downloaded into your microcontroller, and running, but I would really rather that tutorials took it a step further and got the LED blinking under control of interrupt service routines triggered by hardware timer events. That is where you need to get to actually start doing real-world embedded-system programming.
The example actually does use HW timers to blink the LED from a ROS message.
Let me know if you have other suggestions.
This is really a very helpful document, and not just for setting up an ROS controller.