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SAI Audio Clicks and Screen flickers on STM32F7-Eval

Question asked by teal.andy on Jan 7, 2016
Latest reply on May 10, 2016 by FTITI.Walid
Hi,
I've added SAI audio stream to a touchscreen app currently running on the STM32F7 Evaluation board.
The screen has worked fine and I've been using DMA2D (ChromArt) to draw blended images quickly.
However, now I've added some code based on the firmware example SAI_AudioPlay, I find that the audio won't play properly unless I disable DataCache 
(I'm copying the audio from NOR flash to SDRAM and playing it with DMA from there)
On top of the clicking as the audio is playing, the screen is flickering quite badly - even though I'm not doing anything with the Frame buffer while the audio plays.
(When I play the audio from embedded flash at 0x08080000 then the screen doesn't flicker but I do have to disable the DataCache to stop the sound from clicking)


Can anyone point me towards an answer ?
I know I'll have to look at the MPU settings, but not sure if it's related to caching of the SDRAM, embedded flash, the SAI peripheral or all three? 
Could there be some DMA or LTDC settings to look at as well ?




Thanks in advance
Andy

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