[Arm-netbook] HDMI High-Frequency Layout: Recommendations--Taper

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sun Dec 17 04:12:59 GMT 2017

ok sooOo... here's where i'm at so far:

* from the horizontal separation of the big straight i "virtually"
carried them along (or back in the case of TX0 and TXC) so that they
meet TX1 (green)

* i then pushed each track starting point out by a set fixed distance
such that each pair would be EXACTLY 15mil separation from the others
and EXACTLY 5mil separation inter-pair.  this was a bit
trial-and-error but worked fine

* i then, using the same offset pattern, pushed the starting point
diagonally upwards, and also added something like 30 mil to the start
position to move the end point closer towards the end.

now, just to emphasise the problem i'm focussing on at the moment i've
reduced each 45-degree step from its proposed 15mil right down to
1mil.  you can now see clearly that there are two problems:

(1) with the exact same starting offset the intra-pair separation,
which should be EXACTLY 5mil, clearly isn't.  i need to add in an
extra offset of... um... i don't know exactly, it's probably sin(22.5)
* 5.0 or something.

(2) whilst TX2 and TX0 are being adjusted fine, TXC is "racing ahead".
this is because the amount that TXC is supposed to come in is DOUBLE
that of TX2 and TX0.  so i doubled the 45 degree thing and then added
on a FIXED amount (15 mil) but it seems i forgot you'd be supposed to
subtract the 45 degree turning amount FROM the fixed amount, such that
the... you get the idea i'm sure.

anyway it should be fairly clear that there would be no way in seven
hells that this would be at all practical without doing it entirely in
software.  at least thee *fundamental* flaws in my understanding of
how this should and could be done have been uncovered just in the past
2 days alone, each of which would have been SEVERAL DAYS of f*****g
about with manual PADS track layout.

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