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timvideos / HDMI2USB-numato-opsis-hardware

The Numato Opsis board is the first fully open source HDMI2USB board.
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Noise on DisplayPort high speed lines when using the AUX connector #37

Open mithro opened 9 years ago

mithro commented 9 years ago

When Mike tries to use the AUX channel on the DisplayPort connector, it causes the high speed link to drop. We are currently investigating;

From Mike;

Whenever the link is up and stable:

  • If I leave the AUX channel tri-stated then the link stays up.
  • if I waggle the AUX channel to ask the sink for it's status I get the main links drop,
  • There is high frequency 'noise' on the AUX channel when tristated
  • If I drive the AUX channel to 0 or 1 when idle the link doesn't come up.

This is quite probably a side effect of https://github.com/timvideos/HDMI2USB-numato-opsis-hardware/issues/9 -- but we need to confirm.

mithro commented 9 years ago

@hamsternz said;

Tested for a short with a scope and couldn't see anything (watched the lanes while AUX EDID probes were going on).
mithro commented 9 years ago

As the repository has moved forward, I've uploaded an older version of the schematic for the preproduction boards at https://github.com/timvideos/HDMI2USB-numato-opsis-docs/blob/gh-pages/pdfs/NumatoOpsis-schematic-v2-prototype-13-gb1c4312.pdf

mithro commented 9 years ago

Oh wait, that version is still too new. It has the decoupling capacitors. Will need to go back further.