iMX8X higher resolution VGA

Hi All - a good noobie question…

Basically I am trying to get our touch-screen display working at its native 1920x1080 resolution.

It is currently working out of the box (VGA 640x480) with the MX8 in the Iris board, connecting to the DVI connector, a DVI to VGA cable to an adaptor board which drives the screen itself.

I have been trying to adjust the output display timings in a custom overlay, with reference to the screen manufacturers documention, to get the 1920x1080 resolution. But the display seems unable to sync to the settings. It manages to hold a steady image for only about 0.5s fairly soon after booting. After that it’s “aliens taking over” :wink:

I also get the same result with my PC monitor.

So I am fairly convinced that there is some problem with the output from the MX8/Iris. Am I exceeding the hardware limitations of the DAC ?

The display does work nicely with an HDMI-DVI cable coming from my PC. Though this must surely be a digital signal.

Using a digital output would be the prefered option of course - I’m only looking at the VGA option as that’s what we have working out of the box - but I didn’t find any clear clues on how one might enable DVI-D, for example. I am pretty clueless as to the HW components available and how they might be configured ! I presume also through the overlay system…?

So, what should I try next ?

Colibri iMX8X V1.0
Iris r 2.0
Multimedia Demo Image

Hello Timo,

When you use the Iris board the VGA signal is derived from the RGB interface of the colibri SOM.
The most modern SOC do not have an native VGA output. So we have a RGB to VGA converter on the Iris board. see Datasheet Iris 2.0 page 17.

The RGB interface were the VGA signal is derived from has limitation which you can check here.
page 39.
Up to 720p60 (720 x 1280 @ 60 Hz)
•Up to 24-bitcolor(18-bit recommended)
•Supportsparallel TTL displays and smart displays
•Digital video interface output supported with ITU-R BT.656 format•Max pixel clock 85MHz

What are your settings?

Best Regards,

Matthias Gohlke

Hi Matthias !

Many thanks for the reply - yes - I should pay attention to the data sheets - I’m still getting round all the hardware on offer !

So, of course this explains the problem - the hardware will not fare well trying to run the much higher 1920x1080 resolution - at least not at any sensible frame rate.

It looks like a digital alternative is really the way to go.

Hello Timo,

if you let me know what you want to achieve I could try to recommend you a different solution.

Matthias Gohlke

Hi Mathias,

I was trying to get the screen working at its maximum resolution of course :wink: We’ve got that working now using the DSI-HDMI board(s) and another board to drive the screen, which is fine for the prototype.

I had been wondering if the Iris DVI socket could be set up to output DVI-D, which would be a step in the right direction - rather than using the connector on the SoC itself – though it’s not a high priority now I can get on with coding the application UI.

In the end, we would really like to drive the monitor directly via the LVDS, but I think that’s already an open topic which I will leave on the back-burner in the hardware corner of the office :-))

Many thanks,




so like described in the datasheet the DVI/VGA is only applies to the Colibri TX and IMX6.
one way would be to go to an LVDS display.
The dual-channel LVDS interface can support resolutions up to 1920x1200 @60fps (170MHz pixel clock maximum).
So check out our other SOM families as well.

Best Regards,

Matthias Gohlke