How to port MicroPython to a brand new processor?

[ijoffe]

I am part of a group looking to get MicroPython running on a new proprietary board with a custom processor (no existing port).

I have seen the documentation for porting, but are these instructions for porting to a brand new processor or just to a new board?

Is there a guide somewhere on porting MicroPython to a brand new processor (with a different, proprietary ISA)? What steps are required? Is this generally recommended?

Thanks!

[jimmo]

The first main question is what's the compiler and general build system and SDK/HAL for your custom processor.

So for example, if you're required to use non-Make-based build system then you're going to be in for a much harder time. MicroPython works with a range of C compilers, but obviously gcc is going to be the easiest. We don't use any extensions, any C99 compiler should work.

If your system has some sort of RTOS or other similar framework, then you might want to look at the embed port (i.e. embed MicroPython into your existing firmware) rather than write a direct "bare metal" port. (See also #11430)

Most of the complexity of a new port comes from figuring out how to integrate with the vendor SDK/HAL and getting the makefile working.

You can look at the bare-arm and minimal ports, but also some of the newer ports (e.g. mimxrt). The "reference" port is still stm32.

One thing to note, the ISA shouldn't be important (unless you have some specific boot/reset/interrupt config), nothing in MicroPython requires assembly code, except for:

• the NLR (exception handling), but if your platform supports longjmp you can default to that
• the native emitter, but you don't need to enable that

It's hard to give more details without really understanding where you're at. Feel free to ask more questions!

[ijoffe]

Thanks for the quick and detailed response!

Our processor currently does not have any native C/C++ compiler, we use cross-compiling to program C/C++ executables on the board. Does MicroPython require a native C/C++ compiler, or is there a way to port it without this?

[jimmo]

@ijoffe This is completely expected -- almost every target supported by MicroPython is using a cross compiler. (The only exception is the Unix and Windows ports)

[jimmo]

@NoosaHydro your reply (now hidden) was highly inappropriate and a violation of our code of conduct. https://github.com/micropython/micropython/blob/master/CODEOFCONDUCT.md

Please reconsider your approach in further interactions with the MicroPython project.