Do I need a driver for a LCD display (with touch screen) to work?

Technical Support
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1

I would like to connect an LCD to my SOM, likely will through HDMI or LVDS interface. I have some enquiry regarding this:

  • In order for me to display graphic to the LCD correctly (via Qt) and receive the touch screen input, which driver should I acquire/enable?
  • Is the display driver and touch screen driver specific to LCD panel model? Or it is specific to the display controller on the SOM?
  • If there is display driver that is specific to the LCD model, how do I identify it and load it?
  • What should I do if I need to rotate the LCD orientation (e.g. from landscape to portrait)?
2

Dear @kh_ong,

Thanks for reaching out to Toradex.

depending on the SoM and the display you use there are different device tree overlays that you need to enable.

If you follow the guide in “Device Tree Overlays” you will find further down the different files you have to select depending on the setup you have.
Can you specify which display and carrier board you are using?

A popular option to rotate the image is by using qt. Qt-Article here you’ll find an article that will help you getting started with qt. How to rotate the image in qt, is easily available on the web.

Best Regards
Kevin

3

  • HDMI and LVDS drivers are included. You need just to configure LVDS driver to match display parameters. HDMI configured automatically. And you need to point which display output should be used. Please check this article.

  • You will need to install a driver matching your display touch controller. How to get it depends on touch controller used. Many driver are included in kernel source but you need to enable it.

  • Check QT documentation about UI rotation.

4

Thank you so much for the input, @alex.tx and @kevin.tx .

My SOM is Apalis iMX8QXP 2GB ECC IT (and we planned to attach Toradex - DSI to HDMI Adapter to it). I’m currently still in the phase of selecting the LCD, hence would like to understand the selection criteria in term of software/driver requirement. FYI - I’m currently evaluating these 2 LCD:

  1. WF50FSYFGDHGV - Winstar Display
  2. https://www.palmtech.com.tw/product/tft-lcd-module/tft-lcd-module-pt07010260tc-c8-series

Just want to ensure I understand your respond correctly, can you help to answer following questions?

  • For display functionality, we don’t need any display driver that’s specific to the LCD model, we only need the HDMI/LVDS display controller driver (which already included in the BSP). Am I understand this correctly?
  • For touch functionality, I need a driver that’s specific to the touch controller. Am I understand this correctly?
  • For display rotation, it can be achieved through Qt. May I know do I need to also ensure the display driver support rotation? Or it should just work as long as the rotation is done via Qt?

Thanks!

5

  • Yes, but you need to configure driver using Device Tree

  • Yes

  • Yes

6

Thanks @alex.tx ! Last question from me:

For the third question - “Yes” means Qt alone is enough to make the rotation (without specific API from driver), right?

7

Should be enough. Please check QT documentation.