2017-06-16 8:55 GMT+02:00 mike.valk@gmail.com mike.valk@gmail.com:
2017-06-15 21:01 GMT+02:00 Luke Kenneth Casson Leighton lkcl@lkcl.net:
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.
How about having GND tracks parallel to each Tx/Rx pair. Creating a sink for EM signals to drain into instead of crossing over.
---GND----0 ---Tx------[ ] ---Rx------[ ] ---GND----0 ---Tx------[ ] ---Rx------[ ] ---GND----o
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.