[Elphel-support] 10359: cables length and chaining

[Alexander Tsvyashchenko]

Hi Andrey,

On Sun, 13 Dec 2009 16:06:06 -0700, Andrey Filippov <andrey at elphel.com>
wrote:

[skipped]

>> 3. If I understood circuit diagrams correctly, currently ground pins
are 1, 2, 11, 14, 25, 30 - right?
> I would just try to make signal lines

Do you mean having 48 lines (24 signal lines interleaved with ground ones)
and "wiring" them at both ends to 30 pins output?

> That is correct. And we do not plan to make changes to this pinout -
some
> later upgrade may use high speed serial links - then it will be
completely
> different pinout.

But as far as I understood this is not for mid-term future (say, 0.5 to 1
year)? I've seen your post "Sensor interface in 373" about serial I/O in
blog, but is it just an idea for now? Or is it already "in progress" in
some way?

>> 5. Did I understood Constantine correctly that if we're going to order
>> custom flex cables and send them to you - you should be able to perform
>> testing with them?
> Yes, that may be possible. But why not to test them yourself? Because of
> problems to ship cameras to Ukraine?

Yes, one of the reasons is problematic shipment to Ukraine - also
considering the fact that we might need to perform it several times if
several revisions of cables are needed, each time risking loosing
components and/or causing significant delays.

The other reason is that I'm not that confident at all in my abilities to
understand what went wrong exactly if problems surface: you've seen already
how things behave when using long cables and besides that you know your
hardware well, while I would have to start from scratch ...

>> 6. If you have any other hints/suggestions as to the design/ordering of
>> long flex cables suitable for Elphel hardware - I'd be glad and
thankful
>> to
>> get those ;-)
> 
> Not much - I do not have any experience with flex circuits yet. But can
try
> to answer particular questions.

Thanks! ;-) I will certainly contact you when we have those "particular
questions", but for now - still one generic (probably dumb?) question: do
you think that using shielding (something like here:
http://jsbtech.com/Shield%20Flexible%20flat%20cable.html - i.e. having
shield layer connected to ground lines) might help to increase cables
length without going to lines interleaving & flex circuits? I know it is
typically used to cancel noise/emission, but is it possible it might also
help to decrease signal lines interference? Or do you think it's not worth
to investigate that approach at all?

Also, what 12" flex jumpers exactly do you currently use? (I mean
brand/part number)

Thanks!

-- 
Good luck!                                     Alexander