[Arm-netbook] Feedback?

[Richard Wilbur]

Luke,

How are things going? Congratulations on a successful surface-mount board soldering trial of the JAE micro HDMI connector!

I sent my latest recommendations regarding the high-frequency HDMI layout on 1 Sep. I was looking forward to some feedback with respect to some of the questions and suggestions I raised there.

1. Did you receive the message (it referred to 4 images you attached to a previous post)?
2. Does it need pictures showing what I'm talking about?
3. Please let me know if something doesn't make any sense so I can try to explain it better--so it does make sense.

It is very possible that some of the things I recommended can't be done on this layout. That's okay. Let me know and I can see if there is another technique we can use to achieve the same goal or dismiss it as not necessary for a working system.

Sincerely,
Richard
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[Luke Kenneth Casson Leighton]

hi richard, yes, sorry, possible cross-over: sent a message just a few
hours ago, been busy, generated some images after flood-fill, will
look up in the archives the message you're referring to tomoroww.

l.
---
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On Fri, Sep 15, 2017 at 10:33 PM, Richard Wilbur

Post by Richard Wilbur
Luke,
How are things going? Congratulations on a successful surface-mount board soldering trial of the JAE micro HDMI connector!
I sent my latest recommendations regarding the high-frequency HDMI layout on 1 Sep. I was looking forward to some feedback with respect to some of the questions and suggestions I raised there.
1. Did you receive the message (it referred to 4 images you attached to a previous post)?
2. Does it need pictures showing what I'm talking about?
3. Please let me know if something doesn't make any sense so I can try to explain it better--so it does make sense.
It is very possible that some of the things I recommended can't be done on this layout. That's okay. Let me know and I can see if there is another technique we can use to achieve the same goal or dismiss it as not necessary for a working system.
Sincerely,
Richard
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[Luke Kenneth Casson Leighton]

hiya richard, ok yes, took a look at what you wrote,
http://lists.phcomp.co.uk/pipermail/arm-netbook/2017-September/014681.html
and yes, really, a cutout and markup of the bits of the image you're
re referring to would really do it. i've removed the 15mil clearance
design rule, reverted back to the *standard* 6mil clearance that was
is in place everywhere (and is now back in place as the standard
blanket rule, no exceptions, i.e. it's all 6mil clearance from
everything-to-everything.. oh... except the board edge of course,
which is and always was 12mil)

so *part* of what you wrote is slightly out-of-date having done the
flood-fill and also removed the GND spacing tracks... also suggest in
future we refer to the online image names in full e.g.
Loading Image...
as that is unambiguous. so i'll stop sending images to the list and
will use the URLs instead.

l.

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[Richard Wilbur]

Sent from my iPhone

Post by Luke Kenneth Casson Leighton
hiya richard, ok yes, took a look at what you wrote,
http://lists.phcomp.co.uk/pipermail/arm-netbook/2017-September/014681.html
and yes, really, a cutout and markup of the bits of the image you're
re referring to would really do it.

Will see what I can do after looking at the new images.

Post by Luke Kenneth Casson Leighton
i've removed the 15mil clearance
design rule, reverted back to the *standard* 6mil clearance that was
is in place everywhere (and is now back in place as the standard
blanket rule, no exceptions, i.e. it's all 6mil clearance from
everything-to-everything.. oh... except the board edge of course,
which is and always was 12mil)

I'm mildly surprised to hear that the default clearance (everything-to-everything) used to be 6mil: either it changed and I missed the announcement or it was that value before I got involved. The value I understood for minimum clearance was 5mil[1].

The recommendations regarding impedance are based on space-restrictions and the minimum trace size and spacing you quoted as 5mil. The differential pair impedance calculations and recommendations are based on the distance between traces in the pair being near-field and the clearance to other traces putting them in far-field. That's why we're striving to keep the spacing, s, between the traces of the differential pair small so we can achieve far-field (clearance d>=3s) with the other traces (in our limited space).

Post by Luke Kenneth Casson Leighton
so *part* of what you wrote is slightly out-of-date having done the
flood-fill and also removed the GND spacing tracks...

Sounds like progress.

Post by Luke Kenneth Casson Leighton
also suggest in
future we refer to the online image names in full e.g.
http://rhombus-tech.net/allwinner_a10/news/eoma68-a20-275-layer1-hdmi.jpg
as that is unambiguous. so i'll stop sending images to the list and
will use the URLs instead.

I think that is a fine idea. More specific with less guesswork involved.

Reference:

[1] http://lists.phcomp.co.uk/pipermail/arm-netbook/2017-July/014402.html
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[Luke Kenneth Casson Leighton]

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On Mon, Sep 18, 2017 at 2:14 PM, Richard Wilbur

Post by Richard Wilbur
Sent from my iPhone

Post by Luke Kenneth Casson Leighton
hiya richard, ok yes, took a look at what you wrote,
http://lists.phcomp.co.uk/pipermail/arm-netbook/2017-September/014681.html
and yes, really, a cutout and markup of the bits of the image you're
re referring to would really do it.

Will see what I can do after looking at the new images.

thx richard. i didn't do the TX2 double-wiggle, i don't think
there's enough space (because of the GND vias... which i can't remove)

Post by Richard Wilbur

Post by Luke Kenneth Casson Leighton
i've removed the 15mil clearance
design rule, reverted back to the *standard* 6mil clearance that was
is in place everywhere (and is now back in place as the standard
blanket rule, no exceptions, i.e. it's all 6mil clearance from
everything-to-everything.. oh... except the board edge of course,
which is and always was 12mil)

I'm mildly surprised to hear that the default clearance (everything-to-everything) used to be 6mil: either it changed and I missed the announcement or it was that value before I got involved. The value I understood for minimum clearance was 5mil[1].

5 mil - yes, sorry. i didn't check the actual design rules and it's
been a couple of weeks, stuff drops out of my memory quite fast.

l.

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