[Arm-netbook] EOMA68-A20 2.7.4 pre-production prototypes received and working

[mike.valk at gmail.com]

2017-06-16 8:55 GMT+02:00 mike.valk at gmail.com <mike.valk at gmail.com>:

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> 2017-06-15 21:01 GMT+02:00 Luke Kenneth Casson Leighton <lkcl at lkcl.net>:
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>> okaay so the HDMI connection isn't so hot on these 2.7.4 boards.  it
>> works... but there is significant line-interference under certain
>> circumstances, even for 720p50.  1080p60 there is huge amounts of
>> interference resulting in green horizontal lines.  *sigh* i'll just
>> have to have another go at the layout... blech.
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> How about having GND tracks parallel to each Tx/Rx pair. Creating a sink
> for EM signals to drain into instead of crossing over.
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> ---GND----0
> ---Tx------[ ]
> ---Rx------[ ]
> ---GND----0
> ---Tx------[ ]
> ---Rx------[ ]
> ---GND----o
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Looking at the schematics I see that is already being done. I do however
see a lot of gaps between GND tracks. Especially on the blue layer.

Too bad the HDMI pads are so close to each other otherwise you could have
had a GND  track run between them fully enclosing the HS pads.

To the left I see that all HDMI tracks are routed trough some chips. What
are those? Magnetics, impedance matchers? I mention that because on the
blue tracks the'res a log of extra track for matching track length. maybe
that should that be done before those chips.

Also the pads are shortened. I hope that's on purpose.


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