Summary

The Enermax Liqtech XTR AIO cooler has a numeric LCD on the pump head that accepts live data over USB HID. No vendor documentation or prior Linux/liquidctl support existed; the protocol was fully reverse-engineered by iterative black-box probing of the HID interface on a Proxmox Linux host (the Windows companion app could not be used as a reference because GPU temperatures were passed through to a VM, leaving the screen blank).

Protocol (reverse-engineered):

• HID report ID 0x20, 64 data bytes

• Values are 16-bit big-endian, displayed verbatim (no unit conversion by device)

• Three writable display fields:

  Field	Command	Byte offset	Display capacity
  CPU temp	0x01	5–6	4 digits
  GPU temp	0x04	8–9	4 digits
  Pump RPM	0x10	11–12	4 digits

• A secondary CPU field (0x02 @6–7) exists but its hardware renders only ~2 digits; the driver mirrors the primary CPU value there silently.

• Screen blanks if any field is not refreshed within ~2 seconds.

• No sensor data is readable from the device over USB (get_status returns []).

New file: liquidctl/driver/enermax_liqtech_xtr.py

Exposes three channels via set_screen:

liquidctl set cpu screen temperature 45
liquidctl set gpu screen temperature 2065   # GPU #2 at 65 °C  (id × 1000 + temp_c)
liquidctl set pump screen rpm 2900

The id × 1000 + temp_c convention for the GPU field encodes which GPU is currently shown in the leading digit, enabling multiple-GPU cycling from a daemon without needing a separate field.

set_color, set_fixed_speed, and set_speed_profile raise NotSupportedByDriver — the device has no USB-controlled LEDs and pump speed is PWM-controlled via the motherboard header.

New file: tests/test_enermax_liqtech_xtr.py

30 unit tests covering all channels, byte offsets, report length, boundary values, validation errors, and unsupported-method errors.

Tested on

• Proxmox VE 9 / Linux 6.x, Enermax Liqtech XTR 360 (USB 2e3c:0a12)
• All three display fields confirmed working at 1 s refresh cadence