Robb. Knight.

After writing this post and using the new setup for a few days I would occasionally get a delay when changing the volume so I've turned this off but I want to keep the post anyway for reference in the future.

I've been enjoying my new keyboard from 8BitDo but one thing has been bothering me. Unlike the MacOS keyboard buttons, the volumne knob^[1] on the 8BitDo increments or decrements the volume twice on each turn.

Since I wrote that post I switched all my key-mapping needs to Karabiner Elements which is the most developery tool in the land but it's really powerful. I was able to use it to handle my hyper key, remapping the ⌘ and ⌃ buttons, as well as a convoluted system for using a different hotkey with iTerm on different keyboards. But I digress.

KE has a feature called complex modifications which allow you to define key overrides with JSON, literally the worst format for user-editable configuration. The system volume can be controlled with AppleScript so I knew I wanted to run the following script every time the knob was turned. Technically this is running osascript to then run AppleScript from the shell but who cares, you get the point.

osascript -e "set volume output volume (output volume of (get volume settings) + 6.25)

This takes the current volume level and adds 6.25% to it. Why that number? Because there are 16 segments on the usual volume overlay and the standard is to increment just one of those segmenets so 100 / 16 = 6.25.

I then used the event viewer in Karabiner to identify the key code of the volume knob changes: volume_increment and volume_decrement.

Finally, I wanted to limit this change to only volume changes coming from the 8BitDo keyboard. The event viewer also shows the vendor ID of the keyboard so I was able to use device logic in KE to limit it. The final configuration looks like this:

{
  "description": "Fix 8BitDo Volume",
  "manipulators": [
    {
      "conditions": [
        {
          "identifiers": [
            {
              "vendor_id": 11720
            }
          ],
          "type": "device_if"
        }
      ],
      "from": {
        "key_code": "volume_increment"
      },
      "to": [
        {
          "modifiers": [],
          "shell_command": "osascript -e \"set volume output volume (output volume of (get volume settings) + 2)\""
        }
      ],
      "type": "basic"
    },
    {
      "conditions": [
        {
          "identifiers": [
            {
              "vendor_id": 11720
            }
          ],
          "type": "device_if"
        }
      ],
      "from": {
        "key_code": "volume_decrement"
      },
      "to": [
        {
          "modifiers": [],
          "shell_command": "osascript -e \"set volume output volume (output volume of (get volume settings) - 2)\""
        }
      ],
      "type": "basic"
    }
  ]
}