C[omp]ute

From: andrew cooke <andrew@...>

Date: Thu, 26 Jun 2025 18:11:21 -0400

I've just got "hello world" working on the Music Thing Modular (MTM).
Here are a few notes:

- I didn't really follow anyone's instructions or project layout,
  which in retrospect would have made things simpler.

- Instead, I started writing the code I wanted to deploy long before I
  got the machine.  I wrote in emacs and called g++ via a shell script
  to compile.  This worked fine for developing my small project, but I
  just saw CLion is free for non-commercial use, so will probably
  switch to that at some point.

- When I had the machine I realised I needed to do a fair amount of
  work making it "uploadable": I needed to move to CMake, integrate
  with the RPi pico SDK, and get cross-compilation working.

- I run Fedora on my laptop and a quick google suggested
  cross-compiling on that wasn't great.  So I installed Debian testing
  on a VM (Debian is the basis of the RPi linux and seems to have lots
  of support).  What follows is therefore for Debian.

- I moved my project to CMake, which meant splitting into src and
  include directories, and adding the following CMakeLists.txt:

    $ cat CMakeLists.txt 

    cmake_minimum_required(VERSION 3.13)

    #set(PICO_BOARD mtm_computer_16mb CACHE STRING "Board type")
    set(PICO_SDK_FETCH_FROM_GIT on)
    include(pico_sdk_import.cmake)

    project(
      cosas
      VERSION 0.0
      DESCRIPTION "just trying to get cmake working"
      LANGUAGES CXX C)   # C for sdk - https://stackoverflow.com/a/74591212

    include(FetchContent)
    FetchContent_Declare(workshop-computer
			 GIT_REPOSITORY https://github.com/TomWhitwell/Workshop_Computer.git
			 GIT_TAG        main)
    FetchContent_MakeAvailable(workshop-computer)

    pico_sdk_init()
    add_subdirectory(src)
    set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
    set(CMAKE_CXX_EXTENSIONS OFF)
    set(DOCTEST_CONFIG_DISABLE ON)
    add_executable(cosas hello-world.cpp)
    target_compile_features(cosas PRIVATE cxx_std_20)
    target_compile_definitions(cosas PRIVATE DOCTEST_CONFIG_DISABLE)
    target_link_libraries(cosas PRIVATE cosas_lib pico_stdlib)
    pico_add_extra_outputs(cosas)   # generate uf2
    pico_enable_stdio_usb(cosas 1)  # allow serial over usb

  (Note that this includes some stuff I am unsure about, like the
  WorkshopComputer repo - I assume I will need that later).

- Given that, in the same directory this creates the environment:

    $ cat install.sh 
    #!/bin/bash

    cd "$(dirname "${BASH_SOURCE[0]}")"

    sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib g++

    if [ ! -e pico_sdk_import.cmake ]; then
	wget -L https://raw.github.com/raspberrypi/pico-sdk/master/external/pico_sdk_import.cmake
    fi

    mkdir -p build
    pushd build > /dev/null
    cmake ..

- And then "cd build; cmake --build" builds the code.

- This small hello world program doesn't actually use anything I've
  written but ddoes test that deploy works:

    $ cat hello-world.cpp 

    #include <stdio.h>
    #include "pico/stdlib.h"

    int main() {
	stdio_init_all();
	while (true) {
	    printf("Hello, world!\n");
	    sleep_ms(1000);
	}
	return 0;
    }

- Running cmake (above) creates a uf2 file that I can upload tp the
  MTM by following the instructions on their site (basically hold the
  hiddent button down, tap the normal button, and then copy the uf2
  file to the upload diretcory.

- Restarting everything, "cat /dev/ttyACM0" shows the hello world
  message.

There are lots of details missing (feel free to ask, although I have a
memory like a sieve) - this is more to say that it is possible and to
encourage others.

Now I need to actually deploy the code I have...

Andrew