LVDS wire for Iris Carrier Board 2.0

Hello everyone,

I have some questions about how to wire a custom cable to connect the display pannel AUO G133HAN01.0 to a Colibri iMx8 Module through the Iris Carrier Board.

As I can see in the Iris Carrier Board 2.0 datasheet, there is a dedicated LVDS connector with pin designators named as “LVDS_A_TX0_P”.

While display panel datasheet identifies pins like “RxOIN0-”.

What does it means odd and even in this case? I have supposed that A correspond with ODD, and B with even for channles and clocks signals. Is this correct?

Also there is a chronogram with the input data format in pannel datasheet.

Is it related to the electrical connection or only with the signals required to send the image to display?

And my last question is regarding to power and backlight.

AGBSEN does correspond with any line dedicated to Backlight control? Should I map this to any specific pin from X7 carrier board connector?

If you could give me some guidance about this topic it will be very appreciated.

The Iris v2.0 board has an THC63LVD827 LVDS transmitter which converts module’s Parallel RGB output to LVDS. That transmitter can be configured to different modes using Colibri GPIO. Please refer to the THC63LVD827 documentation and Iris board schematic for details.

Sorry but I don’t know purpose of the AGBSEN signal. Please contact display manufacturer.

There is no mention to even and odd in THC63LVD827 documentation.

As I can see in the schematics from Iris Board, the channels seem to be in the same order, so I will try like that.

Please, could you refer me to additional information or point me to what else do I need to know to configure the video signal from an iMX8X board connected to Iris.

Hello Eduardo,

Lets first clarify a few technical things before we dive into the setup. I just want to make sure that we go the right path here since there are multiple options.
since you are mentioning the colibri IMX8x are you aware that the colibri imx8x has a native LVDS port?
So this means that there are two ways to to connect a LVDS Display to the Iris carrier board and to the SOM itself. If you want to be compatible with the Colibri SOM family you should use the way with the RGB to lvds converter like on the IRIS board. But you will be limited to 18bit if you want to use other colibri module from the colibri family. The colibri family does only specify a 18bit standard.
Please read page 38 and following in the colibri imx8x https://docs.toradex.com/105670-colibri-imx8x-datasheet.pdf
“The ColibriiMX8Xprovides one parallel LCD interfaceon the SODIMMconnector. Itsupportsup to 24-bitcolorsper pixel.Only the 18-bit mode is ensured to be compatible with other Colibri modules. The additional signals required for the 24-bit interface are located as alternate functions,which are not located at the same place as on other Colibri modules with 24-bit color support. We recommend using the LCD interface of the Colibri iMX8X only in the 18-bit mode.”
see more also here: Carrier Board Design Guides
colibri copatibility guide

Are you intending to use the Iris 2.0 in production or just for evaluation? Or are you planning to build you own carrier? So depending on this the approach will be different.
please give me a quick feedback and then we proceed from there.

Best Regards,

Matthias Gohlke

Hello Matthias,

We are planning to use the iMX8 and Iris carrier board together in short to medium term. It is not possible we use another SOM different from the iMx8 in any case.

With this set up and using the Iris connector, can we assure 24bits depth? Could you guide us from here a bit on how to make both the connection and the software configuration?

I understand that in case of using the LVDS connector from the iMX8 is neccesary to use an adapter. It is right? Then, with Colibri board in our set up there is no advantage to take that approach.

Hello Eduardo,

Like I said if you want true 24 bit depth with the colibri imx8x you need to build you own custom carrier board, or you have to build and adapter that takes the 24Bit LVDS output that is available only on the IMX8X via the FFC connector that can also output MIPI DSI(x2).

Or if you fine connecting a 24 bit lvds display but only showing 18bit depth pictures. You can use the iris board LVDS
The LVDS interface on the colibri is feed from 18bit parallel and converted to LVDS 24 bit

see datasheet page 40

"The Colibri form factor does not feature a native LVDS interface on the SODIMM connector. However, the Colibri iMX8X is equipped with an additional FFC connector that hosts a dual-channel LVDS interface that can be configured to two independent single-channels. This LVDS FFC connector is not compatible with other Colibri modules. If compatibility with other modules is required, it is recommended to add an LVDS transmitter insteadfrom the parallel RGB LCD interface on the carrier board. Such a transmitter can be found on the Colibri Evaluation Board and is described in the Colibri Carrier Board Design Guide. "

As I mentioned before, we are going to use the iMX8 together with the Iris as a carrier board, with its dedicated LVDS conector (X7). First, we need to know how to make the custom cable correctly, which is my main question.

After this, we need to know if any additional software configuration is required to display the image for that output.

Please, could you give me more guidance about this two topics?

I’m aware that iMX8 has a dedicated LVDS port. Seems there isn’t any adapter or board provided, so to make a custom cable for DF13A connector sounds easier than deal with that.

Thank you for your support

Up!

It’s been a week and I still haven’t received any response

Hi @Eduardo

Sorry for the late reply.

We only made once an adapter which is officially not supported and only for the demo purpose. The schematic of this adapter can be found Electronics_Schematics PDF_Colibri iMX8X LVDS Adapter V1.0 Schematics.pdf (286.2 KB).

Regarding the software changes, you will need an special devicetree as this example.

Best regards,
Jaski

Thank you for your response @jaski.tx

Too bad to read that is not officially supported.

I’ll try to assemble one according to your schematic and check how it goes. I’ll tell you the result or if I have any other question.

Perfect. We will wait for your feedback.

Hi again @jaski.tx ,

With the overlay configuration which you can see below…

overlays.txt
fdt_overlays=colibri-imx8x_parallel-rgb-lvds_overlay.dtbo colibri-imx8x_atmel-mxt-connector_overlay.dtbo display-dpi-lt170410_overlay.dtbo

differential signals measured in the Iris Carrier board X7 connector don’t look properly.

There is no activity in clock lines, and the chanels only remain at 3,3v.

I know that it is necessary to change the device tree for our set up. But I was wonder if with the overlay configuration you provided in this link ( Device Tree Overlays (Linux) (toradex.com)) by defualt, about your 10.1 lvds capacitive touch display may show something.

Could you give me any clarification about this?

Hi @Eduardo

Could you provide the version of the software of the module (uname -a)?

Best regards,
Jaski

Here it is

Hi @Eduardo

The LVDS interface of Iris 2.0 should work. Could you try the latest Bsp 5.4 release? Did you change the devicetee to Iris 2.0 in U-Boot environment?

Best regards,
Jaski

hi @jaski.tx

We have made the test of replacing the load of the compiled device tree at Uboot startup.

image

No luck. We still have no signal.

Our knowledge is very limited about the device tree source configuration for now.

Reviewing the corresponding include I have seen this section, which I attach as an image.

According to the diagrams of the Iris board, I understand that the connection that enables the integrated THC63LVD827 is the one corresponding to the SODIMM 99 line. However, in the comment (code above) it makes mention of the 45.

Could you clarify a little about this?

In the overlays I have dug a little and I also tested default display-dpi-lt170410_overlay.dtbo, and a modified one with another resolution parameters that have been tested by other means on our display panel.

Right now, we are again out of ideas, about what to do to get image on the screen through LVDS. Could you please give us more assistance in this regard?

Thank you four your time.

Eduardo

hi @Eduardo

According to the diagrams of the Iris board, I understand that the connection that enables the integrated THC63LVD827 is the one corresponding to the SODIMM 99 line. However, in the comment (code above) it makes mention of the 45.

You are right SODIMM uses Pin 99 for the LVDS Converter and the PIN45 is used for wakeup.

Right now, we are again out of ideas, about what to do to get image on the screen through LVDS. Could you please give us more assistance in this regard?

Could you share the dmesg log in a text file and output of fbset to see if the resolution is set correctly?

Best regards,
Jaski

hi @jaski.tx

Please find the files you asked attached.dsmeg.txt (31.3 KB)
fbset_out.txt (166 Bytes)

Hi @Eduardo

Sorry for the late reply. Actually all dmesg log looks fine. I really need to test this on my side and I will come back to you soon.

Best regards,
Jaski