Adapting Touchgfx codes to bigger LCD screen

[Krautermann]

I am using Touchgfx for the STM32H745I Disco board. So far it has worked well with the default screen (4.3 inch). But I would like to use a bigger screen. So I will connect the STM32H745I board to a 9 inch screen.

Now my question is, will touchgfx codes still work on the bigger screen with larger resolution?

If not it is not going to work, what modification can I do to make it adapt to the larger 9 inch screen?

[ktrofimo · Accepted solution]

It depends on interface and resolution, not the size. I was successfully running 7" 1024x600 screen with RGB565 interface over LTDC bus. Refresh rate was about 30Hz because higher pixelclock was not supported by the display.

[Krautermann]

Thank you for your reply @ktrofimo​ 

The bigger screen has the same interface RGB888, but the resolution is however different. Bigger screen has 800x480 resolution in constrast to 480x272 from the default screen. Will that be a problem?

As for refresh rate of the bigger screen...I have no idea, it is not mention in the datasheet.

[ktrofimo]

800x480 is not a problem - it should work. My screen have a little bigger resolution and it works.

RGB888 (24 bits) is a maximum bus width but you can easily lower it down to RGB565 (16 bits) with no serious visual degradation. With RGB565 bitmaps you can save 8 pins of the MCU and 30% of the memory size and bandwidth.

Regarding refresh rate: your datasheet should specify front and back porch as well as pixelclock. Knowing this you should be able to adjust LTDC and ​your refresh rate would be a pixelclock divided by total number of pixels (including FP and BP).

For recommended timings you will have

33,3 MHz / (40+800+40​)*(13+480+31) = 72,2 Hz

[Douglas MILLER]

This forum thread was marked by the moderator as needing a little more investigation, so a Support case was created in your name and will be handled off-line. 

[MM..1]

In your question miss important info what mcu on your disco? 128k version is more difficult...

but primary code for new display is more better start with right steps new project as convert existed projects.

[Krautermann]

Hi, the board has STM32H745XIH6, so it's 2Mbytes and not 128KB.