Odroid-VU5 EMC issues

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Odroid-VU5 EMC issues

Unread postby suckiden » Fri Mar 23, 2018 6:25 pm

Hi Everybody,

as the title already says we are having troubles getting the VU5 Display through the electromagnetic compliance test. The Display of course is part of a bigger system and is connected to an odroid-C2.

To give a more precise information the VU5 display considerably exceeds the accepted limits at 226MHz. If necessary I can provide a test chart the next few days. Are you aware of this problem or is this new to you?

As the display is supposed to be part in a commercial product I hope you can help me reducing the noise at 226MHz so we can continue using it. Otherwise I'm afraid we need to change the supplier and that being said, I really like the look and feel of the display ;)

thanks a lot!
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Re: Odroid-VU5 EMC issues

Unread postby odroid » Fri Mar 23, 2018 8:12 pm

That is new to us. Did you connect the Vu5 to the C2 with an HDMI cable? or the small HDMI link board?

BTW, we didn't try the FCC/CE certification for the VU series.
We've passed the FCC/CE regulatory tests for ODROID boards, WiFi modules and power-supplies only.
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Re: Odroid-VU5 EMC issues

Unread postby suckiden » Fri Mar 23, 2018 8:46 pm

The Odroid is connected via HDMI cable, unfortunately due to mechanical constraints we can not use the link board.

I did further research and searched for people having similar problems and found two points we definetly will try out

1. connect all metal framework of the display to each other and important to the casing (system ground)
- I think currently the metal casing of the display is (floating) and not connected to any potential on the PCB (correct me if I'm wrong)
2. Add a ferrite choke on the FFC cable between the DVI to RGB converter and the LCD screen

I know the VU series doesn't have any CE certification, but I'm confident we can adopt the display so it will pass the test.
You're right the C2 looks very good in the test.
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Re: Odroid-VU5 EMC issues

Unread postby suckiden » Mon Mar 26, 2018 5:58 pm

I did some further testing and I now can confirm that the metal frame of the display is floating and not connected to any potential.
So my questions
1. Do you think connecting this to system GND can help reducing emissions?
2. If so, do you have a suggestion how to do this. Unfortunately their is nothing we can screw to. My suggestions using aluminium tape, or solder directly to the frame (as in the picture)

Another way to improve emissions is to add the ferrite on the data line. Do you think this can have an effect?

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Re: Odroid-VU5 EMC issues

Unread postby odroid » Mon Mar 26, 2018 6:10 pm

Generally, any increasing ground path or surface must be helpful for reducing the EMI radiation.

BTW, As far as I searched, the HDMI TMDS clock frequency is 225Mhz and it seems to be the main source of the noise.
So It should be very worth to use a well-shielded HDMI cable with a couple of ferrite cores on the cable.
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Re: Odroid-VU5 EMC issues

Unread postby dmknuth » Wed Apr 11, 2018 9:25 pm

I am interested in reading the outcome of this. We are looking at the Odroid-VU7 and EMC is critical for us.
Are there any plans to adhere to class A or B limits? Are the signals on the board differential?

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Re: Odroid-VU5 EMC issues

Unread postby odroid » Wed Apr 11, 2018 9:30 pm

We have no plan to get a regulatory certification for the Vu series at this moment due to very limited demands.

The HDMI signals are differential. But the LCD 24bit RGB interface uses the TTL-like 3.3V digital logic level signals.
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