OpenLogi0x1981 · backlight
First-generation keyboard backlight control — query and set the on/off state, brightness level, and ambient-light sensor mode.
0x1981 is the first-generation HID++ 2.0 backlight feature for keyboards. It provides host-side control over the keyboard backlight's on/off state and brightness level, and it represents an earlier, simpler design than its successors 0x1982 backlight2 and 0x1983 backlight3. Devices that expose 0x1981 are typically older Logitech wireless keyboards; newer products report 0x1982 or 0x1983 instead.
Not implemented in OpenLogi
OpenLogi's vendored hidpp crate does not provide a typed wrapper for this feature yet. The notes below summarise the HID++ feature in general terms, not OpenLogi behaviour. OpenLogi instead relies on 0x1982 backlight2 where applicable.
What it does
0x1981 exposes a basic backlight control surface for keyboards. The operations it makes available in general terms are:
- Query backlight state — read whether the backlight is currently enabled and at what brightness level.
- Set backlight state — enable or disable the backlight and select a brightness step from the device's supported range.
- Query device capabilities — discover the number of brightness levels the hardware supports and whether automatic (ambient-light sensor) mode is available.
- Receive change notifications — some devices emit an unsolicited event when the user adjusts the backlight directly via keyboard hardware keys.
Because this is a first-generation feature, it does not include the richer effect engine (breathing, waves, reaction), advanced fade-out timers, or writable option flags found in 0x1982. It focuses solely on on/off control and discrete brightness steps.
Status: Not implemented · Feature ID:
0x1981· See also: 0x1982 backlight2
0x1815 · hostsInfo
Rich multi-host management for Bolt/BLE/eQuad devices — enumerate host slots, query pairing status and bus type, and read raw transport descriptors.
0x1982 · backlight
Full keyboard backlight control — read or write persistent config (mode, brightness, effects, fade-out timers) and subscribe to hardware change events.