QMK HID Host

Host component for communicating with QMK keyboards using Raw HID feature.

Requires support on keyboard side, currently is supported by stront.

Architecture

Application is written in Rust which gives easy access to HID libraries, low-level Windows/Linux APIs and cross-platform compatibility.

Supported platforms/providers

	Windows	Linux	MacOS
Time	✔️	✔️	✔️
Volume	✔️	✔️ (PulseAudio)	✔️
Input layout	✔️	✔️ (X11)	✔️
Media info	✔️	✔️ (MPRIS/D-Bus)1	✔️ (Spotify)
Relay	✔️	✔️	✔️
Weather		✔️	✔️

MacOS is partially supported, as I don't own any Apple devices, feel free to raise PRs.

Relay mode (device-to-device communication) - experimental

This allows for communication between two or more devices. qmk-hid-host only receives information from any device and broadcasts it to all devices. The actual sending and receiving should be configured in devices' firmware, but you have to set first byte in the data array - 0xCC for sending and 0xCD for receiving.

Example for syncing layers between two devices:

Data type enum (common between qmk-hid-host and all devices)

typedef enum {
    _TIME = 0xAA, // random value that does not conflict with VIA, must match companion app
    _VOLUME,
    _LAYOUT,
    _MEDIA_ARTIST,
    _MEDIA_TITLE,
    _WEATHER = 0xAF,
    _MEDIA_PLAYER_LINUX = 0xB0,

    _RELAY_FROM_DEVICE = 0xCC,
    _RELAY_TO_DEVICE,
} hid_data_type;

Source device

typedef enum {
    _LAYER = 0,
} relay_data_type;

layer_state_t layer_state_set_user(layer_state_t state) {
    uint8_t data[32];
    memset(data, 0, 32);
    data[0] = _RELAY_FROM_DEVICE;
    data[1] = _LAYER;
    data[2] = get_highest_layer(state);
    raw_hid_send(data, 32);

    return state;
}

Destination device

typedef enum {
    _LAYER = 0,
} relay_data_type;

void raw_hid_receive_kb(uint8_t *data, uint8_t length) {
    if (data[0] == _RELAY_TO_DEVICE) {
        switch (data[1]) {
            case _LAYER:
                layer_move(data[2]);
                break;
        }
    }
}

How to run it

All files are available in latest release.

Configuration

Default configuration is set to stront. For other keyboards you need to modify the configuration file (qmk-hid-host.json).

• devices section contains a list of keyboards
  • productId - pid from your keyboard's info.json. You can get it by running qmk-hid-host -p
  • name - keyboard's name (optional, visible only in logs)
  • usage and usagePage - optional, override only if RAW_USAGE_ID and RAW_USAGE_PAGE were redefined in firmware
• layouts - list of supported keyboard layouts in two-letter format (app sends layout's index, not name)
• reconnectDelay - delay between reconnecting attempts in milliseconds (optional, default is 5000)
• weather - optional weather provider config for Linux and MacOS. The URL should return a temperature value, for example wttr.in/Hamburg?format=%t

Minimal config

{
  "devices": [
    {
      "productId": "0x0844"
    }
  ],
  "layouts": ["en"],
  "weather": {
    "url": "wttr.in/Hamburg?format=%t"
  }
}

Configuration is read from file qmk-hid-host.json in the current working directory. If it is not found, then the default configuration is written to this file. You can specify a different location for the configuration file by using --config (-c) command line option. For example:

qmk-hid-host -c $HOME/.config/qmk-hid-host/config.json

Windows

Manual/Debug mode

1. Start qmk-hid-host.exe
2. If needed, edit config and restart the app

Silent mode

When you verified that the application works with your keyboard, you can use qmk-hid-host.silent.exe instead (like add it to Startup). It does not have a console or logs, and can be killed only from Task Manager.

Linux

1. Update udev rules by running script (remember to update idVendor and idProduct to your values first):

   sudo sh -c 'echo "KERNEL==\"hidraw*\", SUBSYSTEM==\"hidraw\", ATTRS{idVendor}==\"feed\", ATTRS{idProduct}==\"0844\", MODE=\"0666\"" > /etc/udev/rules.d/99-qmkhidhost.rules'

   More info

2. Install runtime dependencies for the enabled providers:

   sudo pacman -S curl

   Linux media info uses D-Bus/MPRIS, so the active player must expose MPRIS metadata. Spotify works out of the box. Other players, like mpv, depend on how they publish metadata.

   The Linux media provider keeps sending the existing MediaArtist and MediaTitle packets, and also sends a compact media text packet using _MEDIA_PLAYER_LINUX = 0xB0.

   Weather uses curl and the configured weather.url; the default expects a wttr.in response like +29°C.

3. Reconnect keyboard

4. Start qmk-hid-host, add it to autorun if needed

MacOS

Note

To configure the weather, you need to replace your Hamburg with your city (example: Cairo); here is its respective repository to see more configurations: chubin/wttr.in - ⛅ The right way to check the weather

1. Download qmk-hid-host

2. Modify qmk-hid-host.json

3. Add your layouts or your local weather, for example:

   "layouts": ["ABC", "Russian"],
   "weather": {
     "url": "wttr.in/Hamburg?format=%t"

   if you don't know what layout are installed in you system, run qmk-hid-host with the layouts listed above, change lang and look at terminal output:

   INFO qmk_hid_host::providers::layout::macos: new layout: 'ABC', layout list: ["ABC", "Russian"]
   INFO qmk_hid_host::providers::layout::macos: new layout: 'Russian', layout list: ["ABC", "Russian"]
   

   "new layout:" is what you need

4. start qmk-hid-host from directory where your qmk-hid-host.json is located

   Note: macOS, by default, may not locate your configuration file correctly. It's recommended to start qmk-hid-host with the configuration file path explicitly specified, for example: ./qmk-hid-host -c ~/Downloads/macos/qmk-hid-host.json

5. If you qmk-hid-host stuck at Waiting for keyboard... there are two common mistakes:

   1. You're wrong with productId in your config. Check qmk-hid-host -p
   2. Close Vial app and try again

Development

Nix

1. nix develop

Native

1. Install Rust
2. Run cargo run
3. If needed, edit qmk-hid-host.json in root folder and run again

Changelog

• 2026-06-19 - add Linux weather and compact media player HID support
• 2025-11-11 - add support for weather and spotify with MacOS
• 2024-10-03 - add support for multiple devices, restructure config
• 2024-09-15 - add MacOS support
• 2024-02-06 - add Linux support
• 2024-01-21 - remove run as windows service, add silent version instead
• 2024-01-02 - support RUST_LOG, run as windows service
• 2023-07-30 - rewritten to Rust

Footnotes

1. Tested with Spotify on Linux, where media metadata is reported correctly. ↩