iMX7D LVDS Display Flicker Issues

Technical Support
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1

Hello,

We have a 10.1" AUO G101EVN01.0 LVDS display connected to the iMX7 RGB interface via a DS90C365A LVDS transmitter. We’re facing issues with display flicker. The colors are accurate and the horizontal/vertical adjustments seem OK to the eye but the display is flickering.

OS: Toradex BSP5

Display timings:

 /* AUO G101EVN01.0 */
			timing_G101EVN01: 1280x800 {
				clock-frequency = <68930000>;
				hactive = <1280>;
				vactive = <800>;
				hfront-porch = <120>;
				hback-porch = <0>;
				hsync-len = <8>;
				vback-porch = <10>;
				vfront-porch = <0>;
				vsync-len = <6>;
				
				hsync-active = <1>;
				vsync-active = <1>;
				de-active = <1>;
				pixelclk-active = <0>;
			};

I’ve tried messing with de-active , pixelclock, hsync, vsync polarities as well as tried changing the LCD drive strengths but the flicker does not go away.

Do you have any suggestions on what I can do?

One other thing to note is that the same display works OK without flicker on an iMX6DL.

2

Hello,
can you provide some datasheet on the display?
Maybe some of the timings are not correct.
Is this a custom carrier board which you are using ? Can you then provide a carrier schematic for review?

Best Regards,

Matthias

3

Hello,

Here’s the datasheet for the display -https://www.distec.de/fileadmin/pdf/produkte/TFT-Displays/AUO/G101EVN01.0_Datasheet.pdf

And the Datasheet for the LVDS transmitter - https://www.ti.com/lit/ds/snls181i/snls181i.pdf

We’re using the Viola Carrier Board.

Thank you!

4

Hello @matthias.tx ,

Have you had a chance to look at the datasheets yet?

Regards,
Atharva

5

Hello atharvalele,

so the RGB to LVDS is this a adapter board you designed?
can you provide more information on this?

Best Regards,

Matthias Gohlke

6

Hello @matthias.tx ,

Apologies for the delay.

Yes it is a board that we designed. I have attached the schematic, Gerber and PCB layout files for the PCB. Let me know if you have any insights.

https://share.toradex.com/y6yr002vg0ujsa8

Thank you!

7

Hello atharvalele,

you mentioned that the same display works fine on the IMX6DL.
YOU: “One other thing to note is that the same display works OK without flicker on an iMX6DL.”
Are you using the same RGB to LVDS adapter there?
And which display configuration you are using there.

Best Regards,

Matthias

8

Hello @matthias.tx ,

Yes we’re using the same display adapter, as well as the same display configuration on the iMX6DL.

The entire hardware is the same, I am only changing the SOM inserted into the Viola board.

9

Hi @atharvalele

Thanks for the information.
As Matthias is in vacation, I will answer.

As a reference, we have the carrier Board Iris 2.0 with the 10" LVDS screen. This combination works well for all the Colibri SoMs. Did you measure the output signals from RGB Interface on iMX7 and iMX6s with an oscilloscope? Did you see any differences?

Best regards,
Jaski

10

Hello Jaski,

Thanks for taking up the issue. Did you have to do any special configuration for the 10.1 display? And is there any difference between the display interfaces on the Iris and Viola carrier boards?

Also, I’m not sure which signals I would probe. Do you have any guide on how to do that?

Thanks,
Atharva.

11

No, there is no special configuration. One need just to have the correct resolution set on RGB Interface and the rest is the work from the LVDS Transmitter.

Can you measure the HSync, VSync, Data Enable and the MSB of R, G, B?

Best regards,
Jaski