AUTHOR: Kevin Shin

1. What is the role of the SBC like Raspberry Pi vs. MCU like Luos, STM32, and Arduino

   • Single Board Computer (SBC) are a miniature computers. It is good at processing large data and complex procedures/programs. I normally think of their role as a human brain which is responsible for decision making in a robot. Due to the small foot print, Nvidia Jetson Nano or Raspberry Pi 3/4 are commonly used in robotics - Reachy uses RPi4.
   • MicroController Unit (MCU) are usually a small electronics circuit boards embedded devices. It does not have a complex Operating Systems (OS) like the SBC, but it does have small set of instructions that continuously runs (loops) a moment it is powered on. Due to its simple architecture and speed, it is commonly used in operating different sensors and motors systems. I normally think of their roles as the human nerves system that is in charge of running your organs like the heart or kidney which operates without you constantly thinking about it. Also the human's quick reflex of moving our muscle is similar to the MCU's driving robots motors. Usually multiple MCUs are deployed in a robot.

2. What is Luos and what role does it play in the humanoid?

   • Luos is ultimately a MCU and it uses STM32 processor which is known for its speed and programmability. You will see Luos boards implemented through out the Reachy robot filling in the role of the MCU like Arduinos. I think it is very possible to build a Reachy robot using RPi and Arduinos.
   • Luos Modular Robotics - Now this is what makes Luos very powerful as it is trying to solve one of the biggest problems in robotics today. Just like the computers in the 1990's, interoperability between the components does not exist and the code you write for a robot is not portable to another robot. Image you buy a database program or a word processor for you computer, but it does not work with your printer. That is the problem Luos is trying to solve by standardizing commonly used components like servos, sensors etc.
   • This video here does a great job in showing Luos modular capabilities - https://www.youtube.com/watch?v=kTr-pwIrRqw&t=2s
   • This video shows the roadmap of where Luos is headed - https://www.youtube.com/watch?v=xQe3z0M_FE8
   • I really do think the technology like Luos will be one of the key enablers for making robotics ubiquitous!

3. What Luos modules are available today?

   • Luos will identify themselves as a software company and the hardware is not their speciality. Luos is currently open sourced, so in the near future, we may see overseas manufactures mass producing Luos modules with different sensors that we can buy.
   • Following commonly used modules are currently available through Luos (Currently, availability is limited for development and experimental use only & not for public use/purchase)
   • https://docs.luos.io/pages/prototyping_boards/boards-list.html

Reference material

• Luos Modules - https://docs.luos.io/pages/low/modules/od.html
• Pyluos - https://docs.luos.io/pages/high/modules_list/angle.html
• Luos Boards - https://docs.luos.io/pages/prototyping_boards/boards_list/usb.html
• Github Luos Examples - https://github.com/Luos-io/Examples/tree/master/Apps/Gate
• Examples - https://github.com/Luos-io/Examples

Key Learning:

• Putting this together actually gave me a clearer picture of the role and components used in Reachy

Issues and Blockers:

• Having a overall view like this may have help understanding Reachy better. Hopefully this will be a benefit to others.