Configure ZMK Firmware In A Subfolder A Comprehensive Guide

Hey guys! Ever found yourself in a situation where you've got this awesome keyboard project, all neatly organized with hardware files and everything, but then you hit a snag when trying to set up your ZMK firmware in a subfolder? Yeah, it's a common head-scratcher. You're not alone! The default ZMK build CI usually expects the config to be at the root of your repository, and it can be a bit tricky to tell it, "Hey, my config's over here!" This guide will walk you through the ins and outs of building a ZMK config that lives happily in a subfolder, so you can keep your projects organized and your keyboards clicking.

Understanding the ZMK Build Process

Before we dive into the how-to, let's quickly touch on how ZMK builds usually work. When you set up a ZMK firmware project, the build system anticipates your configuration files to reside in the root directory of your repository. This is a default setting, intended to simplify the process for most users. However, for those of us with meticulously organized projects or specific repository structures, this can present a challenge. We need to tell ZMK, "Look, the magic happens in this subfolder!" Understanding this default expectation is the first step in customizing the build process to fit your needs.

Why Subfolders?

So, why even bother with subfolders? Well, there are several compelling reasons. Organization is a big one. Keeping your firmware configurations separate from hardware design files, documentation, or other project-related materials makes your repository cleaner and easier to navigate. This is especially crucial for larger projects or when collaborating with others. Imagine a scenario where multiple firmware versions are needed for different keyboard layouts or features; a subfolder structure allows for clear segregation and management of these configurations. Think of it as creating dedicated rooms in your house for different activities, rather than piling everything in one spot. It simply makes life easier.

The Challenge: Default Build CI

The main hurdle we face is the default Continuous Integration (CI) process. CI is a system that automatically builds and tests your firmware whenever you push changes to your repository. This is fantastic for ensuring your firmware works consistently, but it also means the CI needs to know where to find your configuration. By default, it looks in the root directory. When your configuration is tucked away in a subfolder like firmware/zmk, the CI won't find it automatically. This is where we need to step in and provide some specific instructions. The goal is to modify the build process so that it correctly identifies and uses your configuration files, no matter where they live in your repository.

Step-by-Step Guide to Building ZMK in a Subfolder

Okay, let's get down to the nitty-gritty. Here’s a step-by-step guide to configuring your ZMK firmware when it's nestled in a subfolder. We'll cover the key steps and considerations to ensure your build process runs smoothly.

1. Project Structure

First, let's talk about project structure. Imagine you have a main project repository, say my-keyboard-project. Inside this, you've created a firmware subfolder, and within that, a zmk subfolder to house your ZMK configuration. Your file structure might look something like this:

my-keyboard-project/
├── hardware/
│   ├── ...
├── firmware/
│   └── zmk/
│       ├── config/
│       │   ├── ...
│       ├── src/
│       │   ├── ...
│       ├── Kconfig
│       ├── CMakeLists.txt
│   ├── ...
├── ...

This structure is neat and organized. The key is to ensure your zmk folder contains all the necessary ZMK configuration files, such as your Kconfig, CMakeLists.txt, src/, and config/ directories. This clear separation of concerns makes your project more maintainable and easier to understand. Think of it as having a dedicated workspace for your firmware, separate from your hardware designs and other project assets.

2. Modifying the Build Configuration

Now for the crucial part: modifying the build configuration. This usually involves adjusting your CI settings or your local build scripts to point to the correct location of your ZMK configuration. The exact steps can vary depending on your CI system (like GitHub Actions, GitLab CI, etc.) or your local build environment. However, the general principle remains the same: you need to tell the build system to look inside the firmware/zmk subfolder instead of the root.

Using GitHub Actions

If you're using GitHub Actions, you'll typically have a .github/workflows/ directory in your repository containing YAML files that define your CI workflows. You'll need to modify the workflow file responsible for building your ZMK firmware. Look for steps that define the build environment or invoke the ZMK build commands. You'll likely need to add or modify environment variables or command-line arguments to specify the location of your configuration.

For example, you might need to set an environment variable like ZMK_CONFIG_DIR to firmware/zmk. Alternatively, you might need to modify the build command to include a path to your configuration directory. The specific syntax will depend on the ZMK build system and the commands it uses. The key is to find where the build process is initiated and inject the correct path information. This ensures the build system knows exactly where to find your Kconfig and other configuration files.

Local Builds

For local builds, you'll need to adjust your build scripts or command-line invocations. If you're using the ZMK command-line tools directly, you can often specify the configuration directory using command-line arguments. For instance, you might use something like west build -b <board> -- -DZMK_CONFIG_DIR=firmware/zmk. This tells the West build system (which ZMK uses) to use the specified directory for the ZMK configuration. The -b flag specifies the board you're building for, and the -- separates West-specific arguments from those passed to CMake, which is the underlying build system.

3. Setting Environment Variables

One common way to specify the configuration path is by setting environment variables. This can be done both in your CI environment and locally. Environment variables are a flexible way to pass configuration information to your build system without hardcoding paths in your scripts or commands. This makes your build process more portable and easier to adapt to different environments. For example, you might set ZMK_CONFIG_DIR to firmware/zmk in your GitHub Actions workflow file or in your local shell environment.

To set an environment variable in GitHub Actions, you can use the env key in your workflow file. For example:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Set ZMK_CONFIG_DIR
        run: echo "ZMK_CONFIG_DIR=firmware/zmk" >> $GITHUB_ENV
      # ... other steps

Locally, you can set environment variables using your shell's syntax. For example, in Bash, you would use export ZMK_CONFIG_DIR=firmware/zmk. Remember to set the environment variable in the shell session where you're running the build commands. This ensures that the build system can access the configuration path during the build process.

4. Verifying the Build

After making the necessary changes, it's crucial to verify that your build process is working correctly. This involves running a build and checking for any errors or warnings related to the configuration path. A successful build is the ultimate confirmation that your changes have been applied correctly. If you encounter errors, carefully review your configuration and environment settings, paying close attention to paths and variable names.

In your CI environment, monitor the build logs for any error messages. If the build fails, the logs should provide clues about what went wrong. Look for messages indicating that files or directories could not be found, or that environment variables are not set correctly. Locally, check the output of your build commands for similar errors. Debugging build issues often involves a process of elimination, carefully checking each component of your configuration until the problem is identified and resolved.

5. Keeping Your Configuration Up-to-Date

Finally, remember to keep your build configuration up-to-date as your project evolves. This includes any changes to your project structure, ZMK version, or CI system. Regularly reviewing your build process ensures that it remains compatible with your project's current state. For example, if you reorganize your directory structure, you'll need to update any environment variables or paths that refer to the old locations. Similarly, if ZMK introduces new build options or commands, you'll need to adapt your configuration accordingly. Staying proactive with your build configuration helps prevent unexpected issues and keeps your development workflow smooth.

Example Scenario: GitHub Actions Workflow

Let's walk through an example scenario using GitHub Actions. Suppose you have a workflow file in .github/workflows/build.yml. You might need to modify it to look something like this:

name: Build ZMK Firmware

on:
  push:
    branches:
      - main
  pull_request:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v3

      - name: Set ZMK_CONFIG_DIR
        run: echo "ZMK_CONFIG_DIR=firmware/zmk" >> $GITHUB_ENV

      - name: Build firmware
        run: |
          west build -b <your_board_here> -- -DZMK_CONFIG_DIR=$ZMK_CONFIG_DIR

In this example, we've added a step to set the ZMK_CONFIG_DIR environment variable to firmware/zmk. We've then used this variable in the west build command. Remember to replace <your_board_here> with the actual board you're building for. This setup ensures that the ZMK build process knows to look in the firmware/zmk subfolder for your configuration files. This example highlights the flexibility of environment variables in configuring your build process. By setting ZMK_CONFIG_DIR, you can easily adapt the build to different project structures without modifying the core build commands.

Troubleshooting Common Issues

Even with a clear guide, things can sometimes go awry. Let's look at some common issues you might encounter and how to troubleshoot them.

Configuration Files Not Found

One of the most frequent issues is the build system not finding your configuration files. This typically happens when the path to your configuration is incorrect. Double-check your environment variables and command-line arguments to ensure they're pointing to the right location. Look for typos or incorrect directory separators (e.g., using \ instead of /). Also, verify that the files you expect to be in your configuration directory are actually there. Sometimes, a simple oversight like a missing Kconfig file can cause the build to fail.

Environment Variables Not Set

Another common problem is environment variables not being set correctly. This can happen if you set the variable in the wrong shell session or if your CI system isn't picking up the variable. In CI environments, make sure you've defined the variable in the correct scope (e.g., at the job level or workflow level). Locally, ensure that the variable is set in the shell where you're running the build commands. You can use commands like echo $ZMK_CONFIG_DIR to check if the variable is set and what its value is. This simple check can often reveal whether the environment variable is the source of the problem.

Build Errors

If you're encountering build errors, carefully examine the error messages. They often provide clues about what's going wrong. Look for messages related to missing dependencies, incorrect syntax in your configuration files, or other issues. If the error message isn't clear, try searching online for the specific error or consulting the ZMK documentation. Sometimes, the issue might be related to your ZMK version or the board you're building for. Verifying that you're using a compatible version of ZMK and that your board is correctly configured can help resolve these types of errors.

CI Build Failures

CI build failures can be particularly frustrating, as they often involve remote environments and complex configurations. When a CI build fails, start by examining the build logs. They usually provide detailed information about each step of the build process, including any errors or warnings. Look for messages related to file paths, environment variables, and build commands. If the logs don't provide enough information, try adding more logging to your CI workflow to get a clearer picture of what's happening. For example, you can add steps to print out environment variables or list the contents of directories. This extra information can be invaluable in diagnosing the root cause of the failure.

Conclusion

So there you have it! Building your ZMK config in a subfolder might seem daunting at first, but with a clear understanding of the process and a few tweaks to your build configuration, you can keep your projects organized and your firmware building smoothly. Remember, the key is to tell the build system exactly where to find your configuration files, whether it's through environment variables, command-line arguments, or CI settings. Happy building, and keep those keyboards clicking!

By following this guide, you'll be well-equipped to handle the challenges of configuring ZMK firmware in subfolders, ensuring a clean, organized, and efficient development workflow.