I have a weird problem with STM32F746G-DICO board TFT LCD

[Ehsan Daneshvar]

Posted on June 23, 2017 at 09:26

Its very strange to me .. I tried to recognize the problem by checking all datasheets information and search for same situation in the net, but unfortunately I find nothing .. please help me.

the base issue is when i render some thing in TFT lcd and don't change it for a while ( minutes or hours ) and then change it to dark, a light shadow of last image can be seen on the place. it was very surprising to me because as I know this issue was for old CRT displays and not for LCDs and I'd never seen any same problem with my other TFT based LCD projects. so is it true pixels of a LCD could become spoiled because of no changing awhile, or there is other problem that I cant see!!.

an other point is the shadow is faded out and cleared by passing time ( about 10 minutes )  but NOT by reset or power off !!!

[Tesla DeLorean]

Posted on July 02, 2017 at 03:19

https://www.google.com/search?q=screen+burn+in+LCD

 

See also persistence and ghosting.

The least cost panel sourced out of China isn't the route to high quality parts.

[Bogdan Golab]

Posted on July 02, 2017 at 13:29

Unfortunately I see the same problem on my DISCO boards.

[Ehsan Daneshvar]

Posted on July 04, 2017 at 06:52

Actually I'm sure about bad quality off this product's lcd panel because of bad color contrast , a lot of flicking , bad viewing angle and .... but I was surprised because i'd never seen same thing in other bad quality LCD panels , at least not for small periods .. this panel get 

persistence effect in less than one minute ( I've just tested it ) !!!. so i doubt maybe refresh frequency is an important factor and again I can't solve problem by changing refresh rate and pixel frequency in tolerable range. 

[Imen.D]

Posted on July 04, 2017 at 14:28

Hello

Daneshvar.Ehsan

,

Golab.Bogdan

,

Would it possible for you to provide me with your light project to reproduce this problem ?

Thanks

Imen

[AvaTar]

Posted on July 04, 2017 at 14:56

I agree - a common problem with many LCD displays as well, not only CRT.

I've seen panels in industrial applications that were hardly readable at all, for exactly the same reason.

[Bogdan Golab]

Posted on July 04, 2017 at 15:17

@

DAHMEN.IMEN

I just sold the STM32F746G-DISCO board so I cannot show it now.

I have several newer boards (STMF412, STMF469) but I have not tested them yet for this issue - but I only seen it on the mentioned STM32F746G-DISCO board. It was completely new board - one of the first boards sold by the ST.

[Nicholas Yunker]

Posted on July 06, 2017 at 14:22

We recently had the same exact problem but it seemed to resolve itself with future code updates we made unrelated to this issue.  We never figured out what caused the issue.  the RockTech display they use on this eval kit though is pretty good quality.  My company uses RockTech on a number of designs without these issues.  Sorry I can't help you fix the issue, but I can tell you that there is a solution to fix it.

[Imen.D]

Posted on July 06, 2017 at 15:21

Hi

Yunker.Nicholas

,

What is the solution to fix this issue ? updating continuously the Display image? something like Screensaver ?

With Regards

Imen

[Nicholas Yunker]

Posted on July 06, 2017 at 18:11

Unknown.  Like I said, we made unrelated code updates and the problem just went away.  It was a problem we saw really early in development so a lot was added to the code at that point and any of it could have fixed the issue.  I am unable to point to any one thing fixing it.