HDMI EMC issues


We are facing EMC issues with a combination of apalis iMX8 + ixora carrier board + HD ready display at 60 Hz. During the radiated emissions test, we could clearly see that we have a peak from the HDMI signal coming from the ixora to the display (at around 400 MHz). The display itself is certified with class B and we want to certify our machines with class A (so display shouldn’t be the source). Also replacing the ixora with a notebook as HDMI source resulted in a ~10 dB smaller peak.

We will for sure look into different HDMI cables, since we saw a big difference in quality of shielding, but also want to look into adaptions in the iMX8 drivers. We have seen, that one can reduce the drive strength of the HDMI pins, but for now there was no easy way (at least to my knowledge) to adjust the drive strength in the device trees.

Any inputs are welcome on how to tackle this issue - thank you!

Hello @fsidler,

can you provide some information on the Grounding concept you are using and how the GND is connected with the case in which you install the IXORA.

Best Regards,

Matthias Gohlke

Hi @matthias.tx ,

We are grounding the ixora board through all four screw wholes in the corners plus additionally through the extension connectors.

Hi @fsidler,

the mounting holes in the corners are chassis GND and the extension connectors is the signal GND.
They should not be bridged.
I would like to setup a zoom or Teams call with you.

Best Regards,


Hi @matthias.tx

Yes please, can you contact me via mail?