Hello,I have made a custom board based around the STM32F746IGT6 MCU to run a 800x480 display 7in (4DLCD-70800480). I am using external FLASH (MT25QL128ABA1ESE-0SIT) and external SDRAM (AS4C4M16SA-6TIN). I have ran into two main issues so far:The display seems to be flickering at random times, as shown in the first video below (this does not always happen, which makes me think it could be a layout or hardware issue, as I did assemble the board myself). Do you guys have any guidance as what kind of issue could cause this flickering? Could this be a LTDC issue? Here is the video: https://youtu.be/-qseq_30Y88When running animations, there seems to be some "weird" behavior: wrong colors being displayed, and the animated image shifts a few pixels back and forth. From what I read, this seems to be related to SDRAM. I am only using single buffer, as things actually get much worst in double buffer mode, which tells me that my SDRAM might not be setup properly. However, I did implement the SDRAM example from the STM32F746 DISCOVERY BOARD on my custom board, and I am able to write and read to the SDRAM, so I am not completely sure why I cannot get the SDRAM to work in double buffer mode (first buffer at address 0xC0000000, second buffer at address 0xC0119400). Here is the animation video: https://youtu.be/TQ5T-l4oDZUHere is the layout:Here are my clock settings: Any help or guidance is greatly appreciated.Thank you.

I see here more troubleyou show LTDC clock 33 for example for 50Hz you need around 22MHzyour pcb seems be 2 layerSDRAM traces isnt lenght compensatedfor double buffering is recomm start address on bank start for example 0xC02000000memory is 166MHz then try set MCU clock optimized for thisFor test i recomm configure buffer to internal sdram and test ltdc ffunctionality without sdram.

YTalh.1

Associate II

Question

Flickering issues with TouchGFX running a 7in 800x480 display

Forum|Forum|5 years ago
April 16, 2021
3 replies
1559 views

Hello,

I have made a custom board based around the STM32F746IGT6 MCU to run a 800x480 display 7in (4DLCD-70800480). I am using external FLASH (MT25QL128ABA1ESE-0SIT) and external SDRAM (AS4C4M16SA-6TIN).

I have ran into two main issues so far:

The display seems to be flickering at random times, as shown in the first video below (this does not always happen, which makes me think it could be a layout or hardware issue, as I did assemble the board myself). Do you guys have any guidance as what kind of issue could cause this flickering? Could this be a LTDC issue? Here is the video: https://youtu.be/-qseq_30Y88
When running animations, there seems to be some "weird" behavior: wrong colors being displayed, and the animated image shifts a few pixels back and forth. From what I read, this seems to be related to SDRAM. I am only using single buffer, as things actually get much worst in double buffer mode, which tells me that my SDRAM might not be setup properly. However, I did implement the SDRAM example from the STM32F746 DISCOVERY BOARD on my custom board, and I am able to write and read to the SDRAM, so I am not completely sure why I cannot get the SDRAM to work in double buffer mode (first buffer at address 0xC0000000, second buffer at address 0xC0119400). Here is the animation video: https://youtu.be/TQ5T-l4oDZU

Here is the layout:

Here are my clock settings:

Any help or guidance is greatly appreciated.

Thank you.

This topic has been closed for replies.

MM..1

Chief III

I see here more trouble

you show LTDC clock 33 for example for 50Hz you need around 22MHz
your pcb seems be 2 layer
SDRAM traces isnt lenght compensated
for double buffering is recomm start address on bank start for example 0xC02000000
memory is 166MHz then try set MCU clock optimized for this

For test i recomm configure buffer to internal sdram and test ltdc ffunctionality without sdram.