dev: Adding shell.nix for development environments

This adds a shell.nix file to easily create a somewhat reproducible development environment with nix. It does require Nix to be installed, but may be a "lighter" alternative to Docker. Accompanying documentation is also provided.

README.md

@@ -43,6 +43,7 @@ Fast open-source firmware for the [PineTime smartwatch](https://www.pine64.org/p
 - [InfiniTime simulator](https://github.com/InfiniTimeOrg/InfiniSim)
 - [Build the project](doc/buildAndProgram.md)
 - [Build the project with Docker](doc/buildWithDocker.md)
+- [Build the project with Nix](doc/buildWithNix.md)
 - [Build the project with VSCode](doc/buildWithVScode.md)
 - [Flash the firmware using OpenOCD and STLinkV2](doc/openOCD.md)
 - [Flash the firmware using SWD interface](doc/SWD.md)

doc/buildWithNix.md

@@ -0,0 +1,49 @@
+# Build the project using `nix-shell`
+A `shell.nix` file is included in the repository to set up the development environment on systems that have the [Nix package manager](https://nixos.org/) installed.
+It prevents your system from getting polluted with build dependencies while also guaranteeing a reproducible build environment.
+All dependencies and tools required to build InfiniTime will automatically be fetched for you.
+
+## Install Nix
+
+Nix is available for Linux, MacOS and WSL2.
+[Visit the official website for instructions on how to install it.](https://nixos.org/download#download-nix)
+
+## Clone the repository
+
+Before building, local repository must be fully initialized.
+
+```sh
+git clone https://github.com/InfiniTimeOrg/InfiniTime.git
+cd InfiniTime
+git submodule update --init
+```
+
+## Enter the development shell
+
+Creating and entering the development environment is as easy as typing the following command in the project root:
+```sh
+nix-shell --run "$SHELL"
+```
+
+## Build the project
+Two steps are required to build the project: `cmake` and `make`.
+The `shell.nix` file provides a custom script called `cmake_infinitime` that calls `cmake` with the proper paths for the compiler and the SDK.
+
+Inside the shell you can build a target like this:
+```sh
+cmake_infinitime
+make pinetime-app
+```
+
+You can pass additional arguments to the `cmake` script:
+```sh
+cmake_infinitime -DBUILD_RESOURCES=1`
+```
+
+To make use of all the cores your host machine has pass the `-j` argument to `make`:
+```sh
+make -j$(nproc) pinetime-app
+```
+
+There are more targets and configuration options available.
+You can find them in [`buildAndProgram.md`](./buildAndProgram.md).

shell.nix

@@ -0,0 +1,33 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  infinitime-nrf5-sdk = pkgs.nrf5-sdk.overrideAttrs (old: {
+    version = "15.3.0";
+    src = pkgs.fetchzip {
+      url = "https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/sdks/nrf5/binaries/nrf5sdk153059ac345.zip";
+      sha256 = "sha256-pfmhbpgVv5x2ju489XcivguwpnofHbgVA7bFUJRTj08=";
+    };
+  });
+in pkgs.mkShell {
+    # build tools
+    nativeBuildInputs = with pkgs; [
+      cmake
+      lv_img_conv
+      nodePackages.lv_font_conv
+      python3
+      python3.pkgs.cbor
+      python3.pkgs.click
+      python3.pkgs.cryptography
+      python3.pkgs.intelhex
+      python3.pkgs.adafruit-nrfutil
+
+      (pkgs.writeShellScriptBin "cmake_infinitime" ''
+        cmake -DARM_NONE_EABI_TOOLCHAIN_PATH="${pkgs.gcc-arm-embedded-10}" \
+              -DNRF5_SDK_PATH="${infinitime-nrf5-sdk}/share/nRF5_SDK" \
+              "$@"
+        '')
+    ];
+
+    # libraries/dependencies
+    buildInputs = with pkgs; [];
+}