On Aug 18, 2017, at 20:13, Luke Kenneth Casson Leighton <l...@lkcl.net> wrote: > > On Fri, Aug 18, 2017 at 5:51 PM, Richard Wilbur > <richard.wil...@gmail.com> wrote: > >> You bring up an interesting point: what other current return paths are in >> the same vicinity? I have not analyzed that in any detail. At least there >> are no other lines from signal source to signal sink that I know of that >> cross the region of the board where the high-frequency HDMI signals are >> routed. Also, to my knowledge we don't have segmented or restricted ground >> planes that would isolate regions with a higher-impedance reference. > > CEC etc. all follow roughly the same path, on layer 3 (separated by GND). > > i just noticed that SD0 runs round the back of the HDMI 1st set of > VIAS (with no GND separation) on layer 3 - i've removed the SATA power > (not being used) so i can shift them up a bit > > some GPIOs cross on layer 3 as well, just near the GND shielding near > those first vias... > > not much.
Layer 3 always has ground separation from layer 1 in the intervening ground plane on layer 2 and likewise from layer 6 by layers 4 and 5. So I'm not worried about those signals. Regarding the SATA power: Is it an important part of providing a SATA interface? If so, I would suggest not limiting our options on this card. My understanding is that SATA is significantly more efficient for harddisk data interface than USB. Regarding SD0: To what interface does it belong? What is the maximum data rate on this line? _______________________________________________ arm-netbook mailing list arm-netbook@lists.phcomp.co.uk http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to arm-netb...@files.phcomp.co.uk
