STM32F769 - STOP Mode + LCD/DSI - Screen not working on wake up

[ladislas]

Hi there! 

Our product using and STM32F769 + OTM8009A LCD screen (the same as the DISCO_F769) has been working great for quite some time now. We've been using all the drivers provided by ST to have the LCD run and display images or play videos.

Recently, we have been working on enabling `STOP MODE` in our product to reduce power consumption when it's not used.

We've discovered that when exiting `STOP MODE` the screen start behaving strangely until it completely stops working.

It looks like this:

 

(see https://github.com/leka/LekaOS/issues/1074)

Colors are shifting when we turn off (STOP MODE) and turn on (wake up) the video. Position is also shifting. If you do that in a loop, sometimes it "works again" then fails again until it eventually crashes completely.

The PR adding the bug is here:

https://github.com/leka/LekaOS/pull/1173/files

Our guess is that there are issues with the DSI or LTDC clock when STOP MODE / waking up, but we don't even know where to start looking...

Any ideas? :slight_smile: 

Thanks for the help!

Best,

-- Ladislas

[MM..1]

DSI and stop isnt so simple. Read TouchGFX DSI display, not coming out of standby mode.

Plus after wakeup ofcourse PLL need restart ...

[ladislas]

Thanks a lot for the quick answer!

​

So restarting PLL for DSI and LTDC helps a little, but it still eventually stops working. I know the system still runs, but the LCD stays black.

I've read the other post, interesting, but we do not use TouchGFX, we do things by hand. It's hard to know what is really needed and what is TouchGFX related.

Also, their fix calls two methods that I'm unable to find online, so I don't know what they actually do.

I'll ask there.