Waveshare 18.5" HDMI capacitive touch (1920×1080) on Pi 5 – brightness via ddcci-dkms, power via wlopm

[junky84]

Hardware

• Display: Waveshare 18.5inch FHD LCD – 18.5" IPS, 1920×1080, 10-point capacitive touch, optical bonding, HDMI (video) + USB-C (touch), DDC/CI brightness
• Board: Raspberry Pi 5 Model B, 4 GB
• Mounting: adhesive mirror hangers on the back of the display, which simply hangs on two hooks on the wall
• Frame: custom-made wooden floater frame (shadow-gap frame). Besides the look, the gap between frame and display has a practical benefit: warm air can escape, so the panel doesn't build up heat
• OS: Debian 13 (Trixie), labwc (Wayland)
• TouchKio: 1.5.0 → 1.6.0

What works out of the box

• ✅ Touch input via USB-C (HID, no driver needed, multi-touch)
• ✅ Native 1920×1080 resolution
• ✅ Brightness via DDC/CI using the ddcci-dkms kernel driver (/sys/class/backlight/ddcci13) – controllable from HA, e.g. 5 % / 80 %
• ✅ Display power via wlopm (with ddcutil uninstalled – see comments below)
• ✅ On-screen keyboard (squeekboard) for the one-time HA login

Update

The original version of this post described a problem with display power: I had ddcutil installed for brightness, and since TouchKio prefers ddcutil for display status when it's installed (#194), it used setvcp 0xD6 4 – which this panel ignores, so the screen never turned off. My workaround was patching hardware.js to try wlopm first.

Following @leukipp's advice below, I switched to the ddcci-dkms kernel driver for brightness and uninstalled ddcutil. Now TouchKio picks wlopm + /sys/class/backlight on its own – no patching needed. Details in the comments.

[leukipp]

Did you have a look at the ddcci-* apt packages mentioned in the FAQ?

Display brightness can't be controlled through MQTT.

• Have a look at the features section to check if all requirements are fulfilled.
  • The Display MQTT control is a light entity with brightness support. So make sure to click on the entity to test the brightness slider.
  • The brightness slider is also only available if the display status control (on/off) is functional and the user has permissions to modify the brightness value.
• HDMI screens typically do not offer brightness control out of the box, so additional setup steps are required.
  • It's recommended to install ddcci-driver-linux or ddcci-dkms, since this will create the necessary /sys/class/backlight/* folder structure.
  • Additional brightness support using ddcutil is built-in and checked on application startup, but it's really slow and unreliable.
• Make sure that one of these works for your display when you run it directly on the terminal, otherwise the MQTT switch will not show the brightness control.
  • sudo cat /sys/class/backlight/*/brightness returns some numeric value.
  • sudo ddcutil setvcp 10 42 changes the brightness to 42% without asking for a password.

Using ddcutil is more or less Plan C (the fallback of the fallback). So I encourage users to use wlopm for status control and /sys/class/backlight/*/brightness for brightness control, since these have proven to be the most reliable solutions so far.

[junky84]

Thanks, that did it! I installed ddcci-dkms, registered the panel at boot (echo ddcci 0x37 > /sys/bus/i2c/devices/i2c-13/new_device, same approach as in #132) and uninstalled ddcutil, as you suggested in #214 / #194. TouchKio now picks the recommended combo without any patching, verified after a reboot:

Display Status [/sys/class/drm/card1-HDMI-A-1]: ON (wlopm)
Display Brightness [/sys/class/backlight/ddcci13]: 5 (sudo tee)