This is a simple event processor for HID devices (e.g. USB keyboards or headsets) which allows to run a command when a key (e.g. multimedia key or headset button) is pressed.

I got the Bose 700 for free with my new phone but unfortunately the headphones, when connected directly via Bluetooth, don't have any way how I can mute the mic when on a conference call (e.g. Zoom, Teams, Google Chat). So I bought the Bose USB Link that should solve this problem. Unfortunately the muting (long-press on the right hand side ear cup) didn't work out of the box and required to remap the KEY_MICMUTE key to F20 key. That was simply done using UDEV:

sudo cat <<END > /etc/udev/hwdb.d/99-bose.hwdb` evdev:input:b0003v05a7pa310*  KEYBOARD_KEY_b002f=f20  KEYBOARD_KEY_ff990004=f20 END sudo systemd-hwdb update sudo udevadm trigger

Unfortunately this way it didn't visually nor acoustically indicate if the mic is muted or unmuted. That's why I have decided to write HEP which allows to run a script on any event from the headphones without the need to remap any keys.

The script can mute/unmute the mic and change the light color on the Bose USB Link (that makes the headphones to play a sound) using system tools like evtest, pactl and evemu-event.

HEP requires some non-standard packages. Those can be installed by using pip (the requirements.txt file can be found in the HEP Git repository):

pip install -r requirements.txt

On Arch Linux it can be installed using system packages:

pacman -S python-evdev python-yaml

This requires Systemd instance running under a user.

The HEP can be installed like this:

cd ~/ git clone https://github.com/jtyr/hid-event-processor.git mkdir -p ~/.config/systemd/user/ ln -s ~/hid-event-processor/systemd/hep.service ~/.config/systemd/user/ cat <<END > ~/.config/systemd/hep.conf HEP_PATH=~/hid-event-processor/hep.py END systemd --user enable hep systemd --user start hep

cd ~/ git clone https://github.com/jtyr/hid-event-processor.git cd hid-event-processor ./hep.py

Configuration is done by creating a YAML file that contains definition which devices and keys should be monitored and what command to execute when the event appears:

# Configuration for the "Logitech Pro Gaming Keyboard" - device: # Device identification vendor: 0x46d product: 0xc339 version: 0x111 keys: # Play/Pause key down - type: 1 code: 164 value: 1 # Simple command to run command: kcalc # Run on background background: true # FastForward key down - type: 1 code: 163 value: 1 # Simple command to run command: drawio # Run on background background: true # Configuration for the "Bose 700 ACM Headphones" - device: # Device identification vendor: 0x5a7 product: 0xa310 version: 0x111 keys: # MSC_SCAN on KEY_MICMUTE longpress - type: 4 code: 4 value: b002f # Multi-argument command to run command: - ~/bin/bose.sh - toggle # Use the actual device path as one of the command parameters - "{{ device.path }}" # MSC_SCAN on BTN_0 press - type: 4 code: 4 value: ff990004 # Multi-argument command to run command: - ~/bin/bose.sh - toggle # Find a device that has the specivied capability (17=EV_LED, 7=LED_MUTE) - "{{ device[cap=17,subcap=7].path }}" # MSC_SCAN on KEY_PLAY (hangup) - type: 4 code: 4 value: c00b0 # Multi-argument command to run command: - ~/bin/bose.sh - hangup # Find a device that has the specivied capability (17=EV_LED, 7=LED_MUTE) - "{{ device[cap=17,subcap=7].path }}"

The device and key details can be found by using evtest tool.

Jiri Tyr

MIT