Zephyr on Nix

A reproducible Zephyr RTOS project using Nix for dependency management.

Quick Start

Prerequisites

• Nix with flakes enabled

Setup

1. Clone the repository:

   mkdir zephyr_workspace
   cd zephyr_workspace
   git clone https://github.com/dkopka/zephyr_nix.git
   cd zephyr_nix

2. Enter the development environment:

   nix develop

3. Build the project:

   west build -b nrf52840dk/nrf52840

4. Flash to device:

   west flash

5. Debug to device:

   west debug

Project Structure

my-zephyr-project/
├── flake.nix              # Nix development environment
├── flake.lock             # Nix flake lock file
├── west.yml               # West manifest (pins Zephyr version)
├── zephyr/                # Zephyr RTOS (managed by west, gitignored)
├── src/                   # Your application source code
├── boards/                # Board definitions (dts overlays)
└── scripts/               # Helper scripts

Development Workflow

Building

# Clean build
west build --pristine --board nrf52840dk/nrf52840
# or
west build -p -b nrf52840dk/nrf52840

# Incremental build
west build

Flashing and Debugging

# Flash to device
west flash

# Debug with GDB
west debug

Updating Dependencies

# Update west dependencies
west update

# Update Nix dependencies
nix flake update

Key Features

• Pinned Versions: Zephyr version is locked in west.yml
• Reproducible: Nix ensures identical environments across machines
• Fast Setup: Single nix develop command gets everything ready
• Clean: No global installation pollution
• Locked Dependencies: flake.lock ensures exact package versions

Updating nRF Connect SDK Version

1. Update the revision in west.yml:

   -  revision: v3.1.1
   +  revision: v3.1.2

2. Update west dependencies:

   west update

3. Commit the changes:

   git add west.yml
   git commit -m "Update nRF Connect SDK to v3.1.2"

Customization

Adding New Dependencies

1. Python packages: Add to pythonEnv* in flake.nix
2. System packages: Add to buildInputs in flake.nix
3. Zephyr modules: Add to projects in west.yml

Custom Board Support

1. Add board definition to boards/
2. Update build commands to use your custom board

Troubleshooting

Common Issues

"nix flakes are an experimental feature"

echo "experimental-features = nix-command flakes" >> ~/.config/nix/nix.conf

"west: command not found"

• Make sure you're in the Nix shell: nix develop

Build errors after updating

• Try a clean build: west build --pristine --board nrf52840dk/nrf52840

Permission denied on /dev/ttyACM0

• Add your user to the dialout group (Linux)
• Use sudo for flashing (not recommended)

Documentation

• nRF Connect SDK
• Zephyr Documentation
• West Documentation
• Nix Documentation

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Test thoroughly
5. Submit a pull request