Touchgfx TFT Display Flickering Issue

[Chandan Bhatia1]

Hello, I am using display TCXD050ABLON (Data sheet Attached) with STM32F746. As per datasheet I did below LTDC setting and still display is flickering badly.

Few screen shots of display setting as per datasheet is below.

Few Images of flickering display is as below.

Any suggestions?

[Imen.D]

Hello @Chandan Bhatia​ ,

Ensure that you have enough RAM and try improve the performance.

You can have a look on how achieving Better Performance with CacheableContainer, I hope this helps you !

Imen

[Chandan Bhatia1]

@Imen DAHMEN​ Its static images so don't think this problem can occur. Anyway I am using external RAM for it.

Btw did you check my LTDC setting ? Does it look correct as per requited TFT settings?

Can you please check? I put few screenshots of datasheet down in post.

[Alexandre RENOUX]

Hello,

Have you used CubeMX for your LTDC settings ?

Because this should be automatically generated by CubeMX if you put the values in the lTDC settings in CubeMX.

For instance AccumulatedActiveH should be calculated as follows :

AccumulatedActiveH = Vertical Synchronization Width + Vertical Back Porch + Active Height - 1 = 4 + 8 + 480 -1 = 491

Also where is your image stored ? In your external Flash ? If so, are you sure your external Flash is correctly set ?

To check you could store the images in internal Flash or use shapes and boxes to see if you have some artifacts on the screen.

/Alexandre

[Chandan Bhatia1]

@Alexandre RENOUX​ 

I am using internal flash for initial testing. Also have used CubeMX for initial settings. As display was flicking I was changing paraments like AccumulatedActiveH directly from code.

I feel like issue is with horizontal synchronization, vertical synchronization, data enable, pixel clock polarity. Is it fine as per you ?

[Chandan Bhatia1]

I tried below combine too.

[Alexandre RENOUX]

I guess you tried the config LTDC_HSPOLARITY_AL, LTDC_VSPOLARITY_AL, LTDC_DEPOLARITY_AL and LTDC_PCPOLARITY_IPC.

Please try try to remove you image and put a box instead, does it display correctly ?

Could you show me your clock config ?

/Alexandre

[Chandan Bhatia1]

@Alexandre RENOUX​  My clock settings are as below ?

Also Does correct config is LTDC_HSPOLARITY_AL, LTDC_VSPOLARITY_AL, LTDC_DEPOLARITY_AL and LTDC_PCPOLARITY_IPC ?

[Alexandre RENOUX]

Yes I do think that the config I mentioned is the correct one.

Maybe could you try changing the LTDC clock to something lower (9.6 MHz for example like the F746G-DISCO) and see how it behaves ?

/Alexandre

[MM..1]

When i see your images from first post, this dont seems as ltdc trouble. Try check firstly display and ltdc without touchgfx started.

I mean your troble is SDRAM when you use external.

For test only display prepare in flash memory fullscreen image in proper format and replace address in ltdc layer config to this image.

Then in main disable starting touchgfx resp all rtos.

[Chandan Bhatia1]

@MM..1​ Thanks for the comment.

You mean something like below screenshot. Here I replaced "color frame buffer address " to background image array _background_800x480 (generated by touchgfx stored in internal flash) from SDRAM address 0xC0000000. I don't have display with me right now to validate. I will send it to factory for validation.

Why do you feel like that its might be SDRAM issue ? Just wanted to know the reason,

Also I validated external SDRAM using below code. Basically I am checking at random address at bank 1.

void validateSDRAM (void){
	uint32_t uwWriteReadStatus = 0 , BUFFER_SIZE = 100, uwIndex = 0;
	uint32_t aTxBuffer[BUFFER_SIZE] , aRxBuffer[BUFFER_SIZE];
	 /* Fill the buffer to write */
	 Fill_Buffer(aTxBuffer, BUFFER_SIZE, 0xA244250F);
 
	 /* Write data to the SDRAM memory */
	 for (uwIndex = 0; uwIndex < BUFFER_SIZE; uwIndex++)
	 {
	 *(__IO uint32_t*) (0xC0000000 + 0x100 + 4*uwIndex) = aTxBuffer[uwIndex];
	 }
 
	 /* Read back data from the SDRAM memory */
	 for (uwIndex = 0; uwIndex < BUFFER_SIZE; uwIndex++)
	 {
	 aRxBuffer[uwIndex] = *(__IO uint32_t*) (0xC0000000 + 0x100 + 4*uwIndex);
	 }
 
	 /*##-3- Checking data integrity ############################################*/
 
	 for (uwIndex = 0; (uwIndex < BUFFER_SIZE) && (uwWriteReadStatus == 0); uwIndex++)
	 {
	 if (aRxBuffer[uwIndex] != aTxBuffer[uwIndex])
	 {
	 uwWriteReadStatus++;
	 }
	 }
 
	 if (!uwWriteReadStatus)
	 {
	 	SDRAM_Working = true;
	 }
}

[MM..1]

yes as you write static image data and in main add comment to line osKernelStart

 /* USER CODE END RTOS_THREADS */

 /* Start scheduler */

 //osKernelStart();

 /* We should never get here as control is now taken by the scheduler */

 /* Infinite loop */

 /* USER CODE BEGIN WHILE */

 while (1)

 {

  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

 }

in this config you need handle all hw init to ok display, only after this you can use TouchGFX process.

And you ask why SDRAM. TouchGFX use for output only RAM internal or external and all graphics is copied, moved handled in this RAM.

When you set ChromART D2DMA is used for manipulate and may go to timing or other conflict . Your SDRAM test dont test DMA speed transfers.