LCD (HDMI) doesn't display

tanchunhau · July 19, 2021, 7:17am

Hello,

I am facing issue with my LCD display. (It displays nothing).

For Hardware side:

Apalis iMX8 QuadXPlus 2GB ECC IT
DSI to HDMI Adapter (Colibri iMX8X DSI to HDMI Adapter)
5’’ LCD (WF50FSYFGDHGV - WF50FSYFGDHGV - Winstar Display)
A customized carrier board

Note : For DSI to HDMI Adapter (chip address = 0x70), installed at I2C bus 56226000.i2c (i2c-25)

For Software side:

I am using Yocto tdx-reference-multimedia-image.

In device tree

/* Apalis I2C6 (56226000.i2c) MXM3 35, 37 */

&i2c0_mipi_lvds0 {
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = “default”;
pinctrl-0 = <&pinctrl_i2c0_mipi_lvds0>;
clock-frequency = <100000>;
status = “okay”;

 dsi-hdmi@70 {
     compatible = "lontium,lt8912";
     pinctrl-names = "default";
     pinctrl-0 = <&pinctrl_hdmi_int>;
     ddc-i2c-bus = <&i2c0_mipi_lvds1>;
     hpd-gpios = <&pcal6416_1 15 0>;
     reg = <0x70>;
     status = "okay";

     port {
     lt8912_in: endpoint {
             remote-endpoint = <&mipi1_dsi_host_out>;
         };
     };
 };

};

In .cfg (driver file)

CONFIG_I2C_MUX_GPIO=y
CONFIG_SENSORS_LM75=y
CONFIG_GPIO_PCF857X=y
CONFIG_PMBUS=y
CONFIG_SENSORS_PMBUS=y
CONFIG_SENSORS_MAX31785=y
CONFIG_SENSORS_EMC1403=y
CONFIG_FRAMEBUFFER_CONSOLE=y
CONFIG_VT_HW_CONSOLE_BINDING=y
CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y
CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y
CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER=y
CONFIG_FONT_8x8=y

I check i2cdetect -r -y 25, and the lt8912 driver is loaded successfully.

[upload|NcKSABrlJ01xCn6yjb6PWqqYoR8=]

Then I check “dmesg”, and seems doesn’t has any issue.

download dmesg

Result : LCD display nothing after power on.

[upload|hCGmUL7itV5xHeP8Vp4syTdmbXY=]

What else should I do ?
Please guide me, thank you very much.

saijanani.tx · July 20, 2021, 8:21am

Hello @tanchunhau ,

Thank you for your message in the Toradex Community!

Which BSP are you using? Could you please share with us the output of uname -a?

So, I see just the backlight is turned on but no display. Could you maybe try this (video=HDMI-A-1:1280x720) as suggested in the developer article?

Could you also maybe tell us more about when you think this was an issue? Was it working before? What kind of changes have you made so far?

Thanks and Regards,
Janani

saijanani.tx · July 27, 2021, 11:40am

Hello @tanchunhau,

The community is back live, you can post your comment here.

BR,
Janani

tanchunhau · July 27, 2021, 12:33pm

Hi @saijanani.tx ,
thanks for reply.

Which BSP are you using? Could you please share with us the output of uname -a?

Linux NI-SmartRacks-06797155 5.4.91-rt50-5.2.0-devel+git.590db576d04d #1 SMP PREEMPT_RT Tue Feb 2 16:38:41 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux

I am referring to this [Display Output, Resolution and Timings (Linux) | Toradex Developer Center]

In my /boot/overlays directory, only have these .dtbo file, it doesn’t have apalis-imx8_hdmi_overlay.dtbo

I tried to enter key in

video=HDMI-A-1:1280x720

in the terminal, it is still the same. (HDMI LCD display nothing)

Note: I use ssh to remote it. I connected the SOM to my pc via LAN cable.

Could you also maybe tell us more about when you think this was an issue? Was it working before? What kind of changes have you made so far?

This is new, so it never working before. (as mentioned in the post, we have our own customized carrier board)

Please refer to the question post:

The DSI to HDMI Adapter: https://docs.toradex.com/105951-dsi-to-hdmi-adapter-datasheet.pdf

My objective is to make the LCD display something, such as the “console display” (what I see in the ssh terminal)

And play video / Qt GUI application later.

tanchunhau · July 28, 2021, 6:28am

Hi Janani,

Thanks, I already add my comment there. Please help to reply, thanks.

Best regards,

Tan Chun Hau

tanchunhau · July 28, 2021, 11:59am

Hi @alex.tx , if you know the rootcause, please guide me, thanks

tanchunhau · July 30, 2021, 7:29am

Hello @saijanani.tx , @alex.tx , @gustavo.tx

May I get your help to reply please ?
I am stuck at this issue for more than week already (since 19-July)

Thank you.

saijanani.tx · July 30, 2021, 12:23pm

Hello @tanchunhau ,

Thank you for your patience. From your detailed description of the efforts, there seems to be one thing missing. Have you already perhaps enables the device tree overlay?

Here is the link to it on our local repo: https://git.toradex.com/cgit/device-tree-overlays.git/tree/overlays/apalis-imx8x_dsihdmi_overlay.dts?h=toradex_5.4-2.3.x-imx

Please also look at a developer article here on the same topic Device Tree Overlays (Linux) | Toradex Developer Center

Hope this helps. Please let us know if you still have problems.

Best Regards,
Janani

tanchunhau · August 2, 2021, 8:46am

Hello @saijanani.tx ,

Thanks for reply, it is still not working.

I would like to share you my device tree file which is already done the setting that the link you share to me. Please refer to the attachment at below:

imx8qxp-apalis-smartracks.dtsi (19.6 KB)

Please refer to line 256 for

&lt8912_hdmi {
	status = "okay";

	port {
		lt8912_in: endpoint {
			remote-endpoint = <&mipi1_dsi_host_out>;
		};
	};
};

The remaining you can just search through the keyword in my file.

For Hardware:
The DSI to HDMI Adapter (chip address 0x70) is located at Apalis I2C6 (56226000.i2c)
https://docs.toradex.com/105951-dsi-to-hdmi-adapter-datasheet.pdf

The only thing missing is the hotplug (pin 232)

But there is already a hot plug in the DSI to HDMI Adapter and it is connected.

Can you help me check what else is missing ?
Is it possible for me to request your support via online virtual conference ? So I can move forward faster. Thank you.
PS:
If you agree, please send an email to my office email, thanks (I sent to the toradex support once before.)

tanchunhau · August 3, 2021, 1:11pm

Hi @saijanani.tx , @alex.tx , @gustavo.tx ,

Sorry for disturbing,
is there anything is still missing for make it working ?
Is it possible for me to request your support via online virtual conference/meeting ?
This issue is blocking me since > 2 weeks ago.

Thanks

benjamin.tx · August 5, 2021, 8:32am

Hi @tanchunhau , could you have a try with our regular BSP e.g. Linux BSP v5.3. If you have a V1.1A version SoM, download the BSP here. Thess BSPs are not RT-Linux kernel.

tanchunhau · August 5, 2021, 9:10am

Hi @benjamin.tx ,

My SoM is
Apalis IMX8QXP 2GB ECC IT (V1.1B)

Can I just use the BSP ( Linux BSP v5.3) without
1.) config device tree
2.) load driver (.cfg)
??
I will try and update you.

Info :

For DSI to HDMI Adapter (chip address = 0x70), installed at I2C bus 56226000.i2c (i2c-25)
/* Apalis I2C6 (56226000.i2c) MXM3 35, 37 */

DSI to HDMI Adapter (https://developer.toradex.com/products/accessories/add-on/colibri-imx8x-dsi-to-hdmi-adapter )

tanchunhau · August 5, 2021, 9:39am

Hi @benjamin.tx ,

After I reflash the image (Linux BSP v5.3)
PS: My SoM is Apalis IMX8QXP 2GB ECC IT (V1.1B)
Here is the result:
1.) tested with command “video=HDMI-A-1:1280x720”, and it doesn’t work
2.) tested with

# cp /boot/overlays.txt ~/overlays_backup.txt
# echo "fdt_overlays=apalis-imx8_hdmi_overlay.dtbo" > /boot/overlays.txt
# sync
# reboot

Then

video=HDMI-A-1:1280x720

Also doesn’t work:

Here is the dmesg file:
dmesg(5-Aug).txt (39.1 KB)

And only have 3 x I2C bus is enable:
Please read my question, I have mentioned my I2C bus. I am using a customized carrier board.

Below is my LCD (it is on, but display nothing)

Thank you very much.

hai.tx · August 6, 2021, 1:44am

Hi @tanchunhau ,

please try modify overlay.txt with below configuration only, it works for me with Apalis iMX8X without ECC version (which has DSI-HDMI adapter on module).

fdt_overlays=apalis-imx8x_dsihdmi_overlay.dtbo

tanchunhau · August 6, 2021, 2:07am

Hi @hai.tx ,

Please refer to below, it is already using the overlay, but it doesn’t work. (sync + reboot)

I have a question:
Now I am using the image suggested by @benjamin.tx , (Please refer to post at above)
Can I just use the BSP ( Linux BSP v5.3) without
1.) config device tree
2.) load driver (.cfg)
??

But I doubt will it work ? because I am using a customized carrier board, and circuit connection is different.

saijanani.tx · August 6, 2021, 12:24pm

Hello @tanchunhau ,

Thank you for your patience in this regard. It is difficult for us to say exactly why his simply doesn’t work, but I have something here to try out.

Could you please check /sys/class/drm/ to see there is any HDMI interface there?

ls /sys/class/drm

When you find there is a directory card0-HDMI-A-1 (or similar), could you then check the status?

cat /sys/class/drm/card0-HDMI-A-1/status

If it is disconnected then it might be that it is because of the hotplug detect. Then you would have to add a workaround to force that it always stays connected. If the interface is not there at all, then it might be a problem with the lontium chip. This means that you should then measure the I2C signal and see if the iMX8X tries to communicate with the lontium chip.

BR, Janani

tanchunhau · August 12, 2021, 8:37am

Hi @saijanani.tx , @benjamin.tx ,
It is holidays in my country, will check it next week and share you the info, thank you.

saijanani.tx · August 12, 2021, 10:20am

Sure, Enjoy your Holidays

tanchunhau · August 16, 2021, 8:02am

Hi @saijanani.tx,

To answer your question, the HDMI interface is exists but its status show disconnected, please refer to image at below:

The hotplug detect pin(lontium chip) is 2.89V when there is LCD connected, and 0.03V when there is no LCD connected.
Is 2.89V enough to trigger ?

The measurement of I2C signal from iMX8X to lontium chip:
SCL always HIGH
SDA always LOW

Thank you very much.

Jing_Wen · August 16, 2021, 8:50am

Hi @saijanani.tx ,
I am the hardware designer of the board that @tanchunhau is using. I am following the reference schematic provided in Toradex website (https://docs.toradex.com/102388-colibri-hdmi-adapter-v1-0a-schematics.zip), as shown:

However, based on the datasheet, it required me to have a 100K pulldown as well, which I did not put it in because the reference schematic does not have it:

May I know is there any updates needed here?