Interfacing (DSI, CSI, I2C, etc.) • Waveshare 13.3" FHD DSI display oddities

Hi all,

We bought a 13.3" FHD DSI Waveshare display as an evaluation platform for other DSI projects. Also purchased a CM4 2GB Lite No-Wireless and CM4IO board.

With the line in config.txt:
dtoverlay=vc4-kms-dsi-waveshare-panel,13_3_inch_2lane

as suggested by @6by9 here: viewtopic.php?t=384927

I also set display_auto_detect=0, in case it thought this was an official RasPi display (I'd love to buy one, but they don't make a FHD DSI display!) However this option seems to make no difference either way.

I get a 1920x1080p image, at 33.67Hz, which is... an odd refresh rate. But I suppose the Linux kernel drivers do seem to add up to this (since the clock is 56.1% of the 60Hz mode, which matches the VESA DMT for 1920x1080). The image also flickers/shimmers as if the LCD timing is off a little bit which makes sense if the controller is being set up for 30Hz but getting 33.67Hz. Or maybe this is just to be expected with an inexpensive panel. Aside from the shimmering, the image does appear pixel perfect, and the touchscreen works. I'm not too bothered about this.

If I change 2lane to 4lane, the image breaks into two halves and is full of noise, it's completely broken. I was hoping to use this display as a reference test bed for a MIPI project running at 60Hz, as the kernel timings suggest it is capable of such, so would appreciate any support on getting the 4lane mode to work. I could try the Waveshare kernels, but their modules are binary blobs, which is a pain.

Here is what it looks like:I am using latest RasPi OS bookworm with kernel 6.12-25+rpt-rpi-v8. Due to network restrictions at the office, I am unable to update the RasPi OS just yet (but hopefully will be able to do that soon).

Any advice is appreciated.

Thanks!

Statistics: Posted by tom66 — Wed May 14, 2025 5:25 pm — Replies 2 — Views 78

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