STM32F746 + custom LCD display 800x480 LTDC + TouchGFX + FreeRTOS

[pitbull]

Hello everyone,

We have already created a project with working display and other functionalities using stm32F746 discovery board. But, now we wish to switch to custom PCB board and use stm32f746BET6  MCU with custom LCD display from MIDAS i.e. 5000DRT which uses 24bit RGB LTDC pinouts. 

Currently I have changed the LTDC parameters according to the parameters in the datasheet but no matter what changes I make the LCD displays just blank white screen.

I am currently using QSPI to store the touchGFX images and SDRAM for the framebuffer.

We are using Single buffer approach and have verified that the framebuffer at the defined memory location (0xC0000000) has the correct framebuffer data using debugger.

Please find the attached configuration images and LCD datasheet for your reference.

Please guide me for what may be missing and where I am doing something wrong.

Thankyou for your time and consideration.

LCD frequency = 32 MHz

P.S. :- The screen contains a red(0x0505FA) background box and other task is just counting up a global variable for testing purposes. Everything else works fine without any hard faults. 

Regards,

Pitbull

[KDJEM.1 · Accepted solution]

Hello @pitbull,

Could you please check the data enable polarity.

The LTDC control signals (HSYNC, VSYNC, DE, and LCD_CLK) polarities must be configured respecting the
display specifications.
Note: Only the DE control signal must be inverted versus the DE polarity indicated in the display datasheet. The other control signals must be configured exactly like the display datasheet.

If the data enable polarity is active high in the datasheet, it must be configured as active low as mentioned in AN4861 in LTDC control signals polarity configuration paragraph.

Also, I think 7.2.4 LTDC peripheral configuration section in AN4861 can help you.

Thank you.

Kaouthar

[pitbull]

Hello @KDJEM.1 

Thankyou for the quick response I will change the polarity and read the mentioned section and update you accordingly.

Once again thankyou for your help.

Regards,

Pitbull

[pitbull]

Hello @KDJEM.1 

Thankyou once again for pointing out to the correct section to read.

I once again missed out a very critical point in the Application Note.

Note: All GPIOs have to be configured in very-high-speed mode.

I was using the pins in low speed mode and as you mentioned the Data Enable polarity was also to be reversed.

Now successfully able to use the display.

Thankyou!!!

Regards,

Pitbull