No TFT35 SPI KlipperScreen support in the new CB1 Build v3.0

Pilotboy84 · 2025-10-25T16:38:17Z

Hi all, I’m trying to get KlipperScreen running directly on the framebuffer on a BigTreeTech CB1 that’s using an Allwinner H616B chip. It’s running Armbian Bookworm (kernel 6.6.66-vendor-sunxi64, Dec 2024 build) on a Manta M8P V2.0 board with a TFT35-SPI display that shows up as fb_st7796s. The goal is to have KlipperScreen render directly to /dev/fb0 without needing a desktop or HDMI. The framebuffer itself seems fine as the screen shows the BigTreeTech logo on boot, and I can write to it manually, so the driver appears to be working correctly.

KlipperScreen installs fine, the Python environment and dependencies are all in place, but when I launch it, I always get “Gtk couldn’t be initialized.” If I try running it under Xorg, it throws “xf86OpenConsole: Switching VT failed,” which seems to mean the kernel isn’t allowing virtual terminal switching. I’ve tried both framebuffer and Xorg modes, set SDL_VIDEODRIVER=fbcon and FBDEV=/dev/fb0, and even forced it to use SDL directly, but GTK still won’t start. Everything else works normally, it just refuses to render the GUI.

Here’s the kicker: this exact setup worked perfectly on Armbian V2.3.4. KlipperScreen ran out of the box with no special tweaks, so something clearly changed in V3.0 and later builds that broke framebuffer support or GTK initialization. It feels like either framebuffer rendering got dropped, VT switching was removed, or GTK was built without fbdev support.

So my main questions are: was framebuffer (fbdev) support intentionally removed from newer Armbian builds for the CB1? Is VT switching disabled by design in the H616 kernel? And is there any known way to run GTK or SDL apps directly on /dev/fb0 under the current Bookworm build? If it’s just a matter of rebuilding GTK or enabling a missing kernel flag, I’m happy to do that I just need to know where the problem actually lies.

Edited 7 hours ago by Pilotboy84