LTDC: Display Compatibility Question

[KMew]

Hello,

I am looking to use the LTDC (LCD-TFT) feature to interface with a TFT display and potential touch controllers (CTP). I am uncertain on the requirements to interface with it and wanted to confirm a few details.

I have written software (generated by TouchGFX) that works with the STM32H7B3I-EVAL evaluation board. It utilizes a Rocktech display (RK070ER9427-CT).

For our application, we want to use Rocktech as well, but just a smaller screen. Therefore, we are using their RK043FN66HS-CTG. The only mentioned difference is that the 9427 utilizes a different touch controller than the 66HS, so a new driver for that will have to be written. That I understand. I also understand that the pinout is different between the two displays, but they both still have the common pins (R0-7, G0-7, B0-7, HSYNC, VSYNC, DE, CLK).

What I am unsure of is if there's a "LCD-TFT" driver that's device specific. For example, if I have a firmware working with the 9427, then change the resolution in the LTDC configuration (800x480 to 480x272) and change the hardware to match the pinout of the 66HS, will it work with the 66HS? Or is there more to consider than that?

[Osman SOYKURT · Accepted solution]

Hello KMew,

I think there's more to consider. As I can see in the datasheet the RK043FN66HS-CTG uses also a ST7282 Drive IC for TFT, which is not used in the RK070ER9427-CTG. There might be also some clock configuration to consider as you need to render smaller screen now. But it shouldn't be too difficult to change screen and actually you can get inspiration from the STMH7B3i-disco TBS in which there's also a Rocktech display (RK043FN48H-CT672B) but it includes a OTA5180A Drive IC.

Hope that helps

/Osman

[KMew]

Hello Oskt,

Thank you for the reply. I am a little confused by what you mean. Are you saying that, even if I modify the hardware changes between the two displays, I cannot get it to work? Since you are recommending that I change screens. This is supposed to be a TFT compatible screen. Am I misunderstanding?

[KMew]

Hello @Osman SOYKURT​ ,

I apologize for the bump, but I feel I am misunderstanding something.

The 9427 utilizes a "dumb" display (with no controller). I am now using the 66HS, which is a display with the ST7282 controller. So essentially, as long as my board changes the hardware to work with the 66HS, then I CAN get it to work. I just have to set up the LTDC interface correctly and add a driver for the ST7282, is that correct?

In other words, I can get the 66HS to work, but it will involve two changes from the 9427:

• Making a driver for the ST7282
• Changing the timings to account for the differences between the two displays

Is what I've explained above correct?

[Osman SOYKURT]

Hello KMew,

Yes, this is exactly what I've meant 🙂

/Osman