LTDC Configuration for DE-Only RGB Display (No HSYNC / VSYNC) on STM32H743 – Display Not Working

[Anil14721]

Hello everyone,

I am working with the STM32H743BIT6 using the LTDC peripheral to drive an RGB display.

The display I am using does not have HSYNC and VSYNC signals and operates only in DE (Data Enable) mode. I have attached the display datasheet for reference.

Based on the datasheet timing specifications, I configured the LTDC parameters accordingly. Since the display does not use HSYNC and VSYNC, I configured them as constant high signals (logic 1) and set the rest of the LTDC timing parameters as specified.

However, the display is not showing any image. The backlight turns on, but the screen remains black.

Below are the key points of my configuration:

• LTDC peripheral configured according to the display timing parameters from the datasheet
• HSYNC and VSYNC set to constant logic high since the panel works only in DE mode
• Pixel clock configured as per the display requirements
• Data Enable (DE) signal connected and active
• RGB data lines connected correctly
• Framebuffer configured in SDRAM and verified
• Backlight is working, but no visible output on the display

I would like to know:

1. Is there any special LTDC configuration required for DE-only displays on STM32?
2. Should HSYNC and VSYNC be configured differently in the LTDC peripheral when they are not used by the display?
3. Are there any recommended timing values or workarounds for DE-mode RGB displays with LTDC?
4. Is there any additional configuration step that I might have missed?

I would appreciate any guidance or suggestions from the community.

Thank you for your support.

[DmitryR]

Hi @Anil14721 

I do not understand why have you decided that your display has no HSync and VSync signals. They are called HSD and VSD, must be used, and must be configured according to the datasheet.

With best regards,

Dmitry

[Anil14721]

Thank you for your reply, sir. When I reviewed the LCD pins in the datasheet, I noticed that the display does not have HSYNC and VSYNC pins. Based on this, I concluded that the display operates in DE (Data Enable) mode.

I have attached the LCD pin details from the datasheet below for reference. Kindly review them and guide me on the further steps or configuration changes that might be required.

[DmitryR]

Dear @Anil14721 

first of all, it is not very good idea to post separate pages from the datasheet as it may lead to a confusion. The pinout you send now and the time diagram you have sent before have significant discrepances even besides HSD and VSD signals (CLKPOL, data bus naming). In addition the timing diagram has a reference to an "HV mode" and a "DE mode". You should carefully read all this to understand how you LCD really works. The pages you have posted alone raise more questions than give answers. 

With best regards,

Dmitry

[Anil14721]

Sorry for the confusion caused earlier. I understand that sharing only a few pages from the datasheet may lead to misunderstandings regarding the pin configuration and timing details.

To avoid further confusion, I have now attached the complete datasheet of the display module. I kindly request you to please go through the full document and guide me on the correct configuration, especially regarding whether the display should be operated in HV mode or DE mode and how the signals should be mapped.

[DmitryR]

Dear @Anil14721 

First of all I have looked through Internet and I have not found any information about this display neither on developer site nor by resellers. I conclude that this display has an obscured status so I would advise to find some another display. If you still want to use it I would recommend the following:

1. Change the horisontal pulse with from 1 to 28. Despite the display has no HSD and VSD inputs, timing must match. Make sure that Hsync and Vsync outputs of the MCU function correctly despite they are not connected.

2. Make sure the LCD controller is properly initialized in software. 

3. Make sure the display is not in a standby mode. 

4. Play with clock and data enable polarity.

It may also be wise to ask manufacturer to explain all discrepancies in the datasheet.

With best regards,

Dmitry