Ugee graphic tablet Bluetooth connection

Support & help
1

Title

[Bug] Ugee Q8W graphics tablet axes swapped over Bluetooth on FydeOS — pen moves vertically on screen when moving horizontally on tablet

Device info

Tablet Ugee Q8W Wireless
OS FydeOS (amd64-fydeos_iris)
Connection Bluetooth (Bus=0005)
Vendor ID 28bd
Product ID 0946

Bug description
When the Ugee Q8W tablet is connected via Bluetooth, the ABS_X and ABS_Y input axes are swapped. Moving the pen horizontally across the tablet causes vertical cursor movement on screen, and vice versa. The tablet surface is physically landscape (1057x762mm) but the input is being interpreted as portrait.

This does NOT happen over USB/wired connection — wired mode works perfectly. The bug is specific to Bluetooth mode on FydeOS. The same tablet works correctly over both Bluetooth and USB on Windows.

Steps to reproduce

  1. Pair and connect Ugee Q8W tablet via Bluetooth
  2. Open any application (e.g. canvas, drawing app, or simply observe cursor)
  3. Move pen slowly from left to right horizontally on the tablet surface
  4. Observe cursor moves vertically (up or down) instead of horizontally
    evtest evidence (raw kernel input)

When moving pen left to right horizontally, evtest /dev/input/event18 shows:
ABS_X: 24275 → 22599 (change: ~1700 — barely moves)
ABS_Y: 6659 → 17600 (change: ~11000 — moves 6x more)
ABS_X and ABS_Y are swapped at the kernel evdev level over Bluetooth. Both axes have range 0–32767.

libinput list-devices output
Device: Q8W Pen
Kernel: /dev/input/event18
Size: 1057x762mm
Capabilities: tablet
Calibration: n/a

What was tried

  • udev rule with EVDEV_ABS_00 / EVDEV_ABS_01 — not applied (libinput ignores calibration for tablet tool devices)
  • udev rule with LIBINPUT_CALIBRATION_MATRIX — not applied for same reason
  • xinput coordinate transformation matrix — xinput not available on FydeOS host shell
  • Writing udev rules to /etc/udev/rules.d/ — filesystem is read-only even in developer mode

Expected vs actual behavior

Expected
Horizontal pen movement maps to horizontal cursor movement, same as USB mode and Windows Bluetooth mode

Actual
Horizontal pen movement causes vertical cursor movement. ABS_X and ABS_Y are swapped at kernel level over Bluetooth only

2

You can use mount -o remount rw / to disable the read-only mode. Devices like these knockoff tablets often use components that are not supported in mainline Linux, so the issues you’re encountering are quite common. Even with dedicated adaptation, they may not necessarily be fixable.

3

thanks for the reply
yes we can mount I realized that but my question is that we should have problems on both the wired and Bluetooth but the wired connection works fine only on Bluetooth , the mapping should to rotated 90 degrees but its not
and the thing which makes me mad is why I am unable to change the mappings my self

4

You can try Ubuntu. Most likely, you’ll run into the same issue.