Nim for Arduino

Let's start with a warning: this project is only an experimental hack. The Arduino development environment does not support other languages then C++, and the authors of the Arduino IDE have not shown any interest in allowing 3d party langauge integrations. To make this work, we create a fake compiler that looks like a C++ from the perspective of the Arduino IDE, but is actually a wrapper around the Nim compiler.

The current status of this project is "Works For Me, but Don't Complain If It Doesn't For You". I am interested in any improvements, patches or other ideas to make this work better.

There are two distinct parts to this project:

• The host side: on the host the Arduino toolchain is reconfigured to use the Nim compiler by changing the normal recipes, this is done my overwriting some Arduino IDE parameters in a platform.local.txt file. Instead of invoking the normal AVR compiler, it will now invoke the nim_arduino tool, which will cross-compile the sketch with the Nim compiler.

• The Arduino side: in the sketch the arduino module can be imported, which provides the binding from Nim to the usual Arduino standard library.

Setup

• If running from git, first do nimble install to build the nim_arduino tool, and nimble develop to make the library available in your default .nimble repo.

• Symlink or copy platform.local.txt into $ARDUINO/hardware/arduino/avr

• Make sure ~/.nimble/bin is in your $PATH

• Write your sketch and type Ctrl-R to compile as usual.

Note: the below configuration will reconfigure the default toolchain for the Arduino IDE, so you can no longer compile normal sketches. I am looking for a way to make this configurable, but that might require some changes from the upstream Arduino developers. For now, simply remove the platform.local.txt file from the arduino tree to restore the original configuration.

Example

import arduino

setup:
  pinMode LED_BUILTIN, OUTPUT

loop:
  digitalWrite LED_BUILTIN, HIGH
  delay 500
  digitalWrite LED_BUILTIN, LOW  
  delay 500

Misc

When using multiple source files, the Arduino IDE will concatenate all of those and feed them to the compiler, so this will not allow Nim to use the usual import mechanism. Instead, you can enable code reordering feature in Nim to make this work as expected: use the following pragma at the top of your sketch:

`{.experimental: "codeReordering".}`