cancel
Showing results for 
Search instead for 
Did you mean: 

LTDC CLK for 16bit RGB on a STM32L4+ having issues where there is a vertical line on the display.

APesi.1
Associate

0693W000008x4XnQAI.pngThe vertical Line seems to go away when I put a my finger on the LTDC CLK pin. I adjusted the clock frequency to above the minimum (12.5MHz) required for the display, and it still appears. I then added a 40k pulldown resistor to the LTDC CLK pin, and it went away, but I don't see any information anywhwere regarding the addition of the pulldown is an ok solution. I have read another post about the exact same issue, but the issue was closed out with no solution. Any help is greatly appreciated.

1 ACCEPTED SOLUTION

Accepted Solutions

Thanks for the Suggestions! We found a Fix!

Before the fix the LTDC CLK looked like:0693W000008x5RCQAY.jpgThe line GPIO_InitStruct.Speed = GPIO_SPEED FREQ_MEDIUM (5 to 25MHz) was originally set to GPIO_InitStruct.Speed = GPIO_SPEED FREQ_LOW (0 to 5MHz).

0693W000008x5UuQAI.pngAfter the code change:

0693W000008x5WHQAY.jpgStill has some ringing in the clock, but its working much better.

Thanks for the suggestions.

View solution in original post

4 REPLIES 4

>> but I don't see any information anywhere regarding the addition of the pulldown is an ok solution.

Probably not really addressing the problem.

Seems to be more of a display side issue. What does the signal look like on a scope?

If it has a lot of ringing or overshoot, you might want to consider a series resistor, or look at dropping the slew-rate (SPEEDR) of the GPIO pin.

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..
Imen.D
ST Employee

Hello @APesi.1​ ,

It seems the issue is with your code/configuration.

I would suggest adding more details about your configuration, so that Community users can help you.

Imen

When your question is answered, please close this topic by clicking "Accept as Solution".
Thanks
Imen

Thanks for the Suggestions! We found a Fix!

Before the fix the LTDC CLK looked like:0693W000008x5RCQAY.jpgThe line GPIO_InitStruct.Speed = GPIO_SPEED FREQ_MEDIUM (5 to 25MHz) was originally set to GPIO_InitStruct.Speed = GPIO_SPEED FREQ_LOW (0 to 5MHz).

0693W000008x5UuQAI.pngAfter the code change:

0693W000008x5WHQAY.jpgStill has some ringing in the clock, but its working much better.

Thanks for the suggestions.

Imen.D
ST Employee

Thank you for your update.

Glad to know that the issue is solved :smiling_face_with_smiling_eyes:

When your question is answered, please close this topic by clicking "Accept as Solution".
Thanks
Imen