Peter Ampt

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6 years, 4 months ago.

DISCO-F746NG LCD Flicker Problem

I have a problem with LCD flicker on the DISCO-F746NG board. The LCD horizontal flicker episodes last 67 seconds, commence 27 minutes after reset then occur at 71 minutes intervals. Here is a poor quality picture from the motion-sensitive security camera that we used to capture these events over a day.

/media/uploads/pampt/lcd_flicker.jpg

Forum posts from other sites reporting the same problem suggested issues with the use of floats or FreeRTOS but these are not applicable to our application. mbed 2 and mbed-os give the same result. I am using unmodified ST BSP and LCD libraries and those from here https://os.mbed.com/users/MikamiUitOpen/code/F746_GUI/ .

Any advice would be really appreciated.

The LCD flicker issue was fixed by disabling the data cache at the start of main(); there is a resulting performance penalty but it is not noticeable in my application.

SCB_CleanDCache(); // Clean the entire data cache
SCB_DisableDCache(); // Disable the entire data cache
posted by Peter Ampt 17 Aug 2018
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