I have a display from an Anycubic Kobra Neo 3D printer (presumably ST7789V). I'm trying to get it working on a Raspberry Pi running Raspberry Pi OS (Bookworm).

My config.txt:
text During boot, when the screen is being updated intensively, I can see an image, but then it disappears. When running kmstest --device=/dev/dri/card0, the image appears momentarily.

Through experimentation with a Python script, I came to the following conclusion:

Before sending a command, the DC pin is set to 0 (command mode) - the image is visible.

During command transmission - the image is visible.

Before sending data, the DC pin is set to 1 (data mode) - the image is only displayed while data is being transmitted.

If after data transmission ends, DC isn't changed and remains high, the screen turns off.

I checked the DC pin state with a multimeter and it remains high when there are no screen updates.

I tried to fix the issue by modifying the kernel module code and adding a pull-down to low level at the end of data transmission (more details here: https://github.com/notro/panel-mipi-dbi/issues/22) and it worked!

But this solution will only work until the next kernel update, after which I'll have to patch and rebuild the kernel again.

I'd like to know how to make DC go low after data transmission?
PS: The fbtft,st7789v driver doesn't give the desired result - with it, the display flickers and shows a negative image.

Have you definitely got good 3V3 and GND connections to the display?

where did you get that 'neopixel' binary from?

pretty much expect your problem is because of that. used ST7789V with several displays without any issue.
your SPI speed looks also quite low
Change that to 'speed=48000000'

aBUGSworstnightmare wrote: ↑

Mon Oct 27, 2025 6:29 pm

where did you get that 'neopixel' binary from?

pretty much expect your problem is because of that. used ST7789V with several displays without any issue.
your SPI speed looks also quite low
Change that to 'speed=48000000'

I created the neodisplay.bin firmware by following the instructions provided here: https://github.com/notro/panel-mipi-dbi/wiki.

For the initialization commands, I used the source code from this firmware: https://github.com/jokubasver/Kobra_Neo ... 12-L406C12

The contents of my neodisplay.txt file are as follows:
text
I intentionally set the SPI bus frequency to a low value. At higher frequencies (8-60 MHz), the entire initialization process happens instantaneously, which creates the illusion that the screen is not working at all. At the lower frequency, the data transfer is slow enough that I can see the image appear while the transmission is in progress.

This confirms that the issue is specifically related to the DC pin. If you'd like, I can provide a video to demonstrate this behavior.

PhilE wrote: ↑

Mon Oct 27, 2025 5:39 pm

Have you definitely got good 3V3 and GND connections to the display?

My display is powered by 5V. Yes, it's higher than 3.3V, but the display board has a 5->3.3V converter. So the display gets enough power.

R0cketRacc00n wrote: ↑

Tue Oct 28, 2025 9:47 am

PhilE wrote: ↑

Mon Oct 27, 2025 5:39 pm

Have you definitely got good 3V3 and GND connections to the display?

My display is powered by 5V. Yes, it's higher than 3.3V, but the display board has a 5->3.3V converter. So the display gets enough power.

I'm switching on all my ST7796 based module with below sequence so would suggest you remove the MIPI_DCS_EXIT_SLEEP_MODE from the beginning and put it to the back. Also suggest to add MIPI_DCS_ENTER_NORMAL_MODE.

Which display is that exactly? Do you have the data sheet?