alt Hacker Newsre: common lisp shines at low-level tasks like microcontroller programming
While I couldn't find an explicit declaration of this in the linked article, the tunnel system likely has something on the level of an SBC (think raspberry pi) rather than a microcontroller. Common Lisp makes it possible to do fun low-level assembly stuff but AFAIK none of the implementations can run on a microcontroller.
There's uLisp, which builds on Arduino's libraries but it isn't a Common Lisp implementation.
In terms of bare-metal CL implementations there is Movitz (stopped development) and Mezzano, but I don't think those can run on any microcontrollers.
There are also some libraries to convert CL to C, thinlisp and CLiCC, but these aren't actively maintained currently.
The possibility of porting Clozure CL to the RP2040 was discussed in the ccl mailing list last year, but I don't think anyone's working on it.
It probably doesn't make sense to cram a whole Lisp into a constrained environment like a microcontroller. What some people do instead is define a smaller Lisp which acts as a DSL and is compiled to run on the constrained platform.
https://en.wikipedia.org/wiki/Game_Oriented_Assembly_Lisp is an example of this approach.
"GOAL does not run in an interpreter, but instead is compiled directly into PlayStation 2 machine code to execute. It offers limited facilities for garbage collection, relying extensively on runtime support. It offers dynamic memory allocation primitives designed to make it well-suited to running in constant memory on a video game console. GOAL has extensive support for inlined assembly language code using a special rlet form, allowing programs to freely mix assembly and higher-level constructs within one function."