IMX8ULP-EVK display does nothing in Linux

[Keith5]

Hi,
I am running an IMX8ULP-EVK with HDMI display and 5.5" touch LCD connected. I get a small Uboot image on the 5.5" LCD during boot, but then nothing on either once Linux starts.
The terminal serial works and I have used UUU to update to the latest binary image.

[Keith5 · Accepted solution]

Many thanks Brian.
The problem was the monitor I initially used was actually DVI with a converter cable. A native HDMI monitor works fine.
Thanks, Keith.

[Keith5]

I just re-read the getting stated guide, it says "On boards where the NXP Demo Experience is available, an NXP Logo is displayed on the top left-hand corner of the screen"

Is the Demo Experience GUI available on the  IMX8ULP-EVK?
Thanks.

[brian14]

Hi @Keith5, 

Thank you for contacting NXP Support.

Yes, the Demo Experience GUI is available for the iMX8ULP-EVK.

However, in the i.MX8ULP processor the HDMI is not supported and the EVK use a converter from MIPI-DSI to HDMI. This converter is connected using a multiplexer that manages the input to obtain the output signal from MIPI-DSI connector or HDMI connector.
The multiplexer is controlled by a signal PTH9_MIPI_SWITCH that comes from an I2C port expander. By default, this signal is 0 that provides the output to the HDMI connector.

You can try testing and be sure that this signal is in a low voltage to properly use the HDMI connector. To do this you can ensure that the I2C signal is sending the correct value using Linux and measure the voltage of the output from this port expander. Here is a schematic from the port expander.

Also, this signal is also on U55, U56 and U57 of your EVK, you can measure these signals.

Please try and tell me your results.

Have a great day!