Linux Fu: Navigating the Affordable Macropad Dilemma

You can now find inexpensive, generic macropads that come in various configurations, ranging from simple keypads with just a few keys to more complex setups featuring numerous keys, knobs, and LEDs. While established brands typically offer macropads that run on QMK firmware, cheap alternatives may require downloading Windows-only software from dubious sources, leaving users to wonder about their compatibility with Linux systems.

If you’re content with the macropad performing its default functions, which typically just involve basic HID capabilities over USB or Bluetooth, it’s less of a concern. However, if you want to customize the key mappings—since many of these devices send predefined key characters—you’ll have to engage in some reverse engineering. Fortunately, resources like this GitHub repository provide tools for remapping common macropads based on CH57x chips.

Open Source Tool for Configuration

Thanks to Mikhail Trishchenkov, there’s a Linux-compatible tool available for configuring your macropad easily. You can compile it from source or simply download pre-built versions for Linux, Windows, and Mac. Written in Rust, the tool is accessible for modifications if desired.

While the configuration process might not cater to GUI enthusiasts, it will resonate well with most Linux users accustomed to editing YAML files. Upon initializing the tool, you’ll need to specify your specific macropad model before diving into key configurations.

The YAML file format has various keys that you can define:

• orientation: Set your pad’s orientation to its natural position or any rotation you prefer, which helps make the key layout intuitive.
• row and columns: Depending on the layout, define how many rows and columns your pad contains, keeping in mind that the orientation may affect this.
• knobs: Count the number of knobs available on your pad.
• layers: Assign multiple layers, though less expensive pads might only support a single layer.
• buttons: Define the keys within each layer, organized by rows or columns.
• knobs actions: Specify actions performed on clockwise and counterclockwise rotations for each knob.

You may refer to the sample mapping file for guidance on setup.

Getting Started

I renamed the tool to macropad-tool for convenience. Once you prepare your YAML file correctly, you can validate and upload it with the following commands:

macropad-tool validate myconfig.yamlmacropad-tool upload myconfig.yaml

Overcoming Initialization Challenges

One recurring issue is that the macropad must be reinitialized each time you use it. Additionally, to write to the device, typically one must execute commands as root, which isn’t the most convenient. If you want specific keys to perform particular actions (like launching applications), it can become tedious, especially with pads that lack support for layers.

Creative Solutions

Using the KDE keyboard shortcut configuration, you can map keys to perform various actions. I initially set my keypad to generate unused function keys (F13-F25), but ended up mapping keystrokes with combinations of control keys that are less likely to conflict with existing mappings, such as Control+Alt+Shift+A, B, etc.

The challenge remains to streamline the initialization of the macropad. An effective solution could involve creating a root-owned script with sticky permissions to allow users to run the macropad configuration without needing to provide a password each time.

I placed the tool in /usr/local/bin and the configuration files in /usr/local/share/macropad and crafted a script that runs with sudo permissions without requiring a password:

alw ALL=(ALL) NOPASSWD: /usr/local/bin/macropad-tool

Alternatively, you could establish udev rules to set the correct permissions for your macropad directly.

Making Layers Work

While the tools allow for defining layers, achieving true layer functionality requires clever workarounds. For instance, running the loading script with specific arguments via shortcut keys provides a basic layer-switching experience.

Set everything to initialize on system startup through available options like /etc/rc.local, systemd, or udev rules, ultimately creating a more user-friendly environment tailored for a wide range of tasks.

For those interested, these cheap macropads not only present a cost-effective alternative but also offer opportunities for customization and enhancements through software like QMK.

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