[Arm-netbook] Schematic and PCB layout CAD files

[Luke Kenneth Casson Leighton]

On Fri, May 31, 2019 at 3:47 PM Paul Boddie <paul at boddie.org.uk> wrote:

> Also, the A10 news page has mentions of these dimensions from several years
> ago:
>
> http://rhombus-tech.net/allwinner_a10/news/
>
> However, the PC Card documentation indicates that the actual housing of such a
> card is only 54mm wide, so I don't see how existing PC Card housings would
> accommodate such a PCB.

 that's what cost USD $15k when the engineer we paid didn't read the
spec properly.  i told him to source one of the caseworks, measure the
INNER dimensions of the area as defined by the plastic, and use those.

 he FAILED to listen, and instead produced a PCB of the OUTER
dimensions that, clearly, wouldn't even fucking well fit inside the
fucking case.

 he also failed to run basic DRC which showed that he'd added a power
track that shorted across a GND pad.


> I do remember that EOMA68 cards (maybe of an earlier generation) were
> produced.

 yes.

> Then again, looking at the A10 news page, there is a picture of a
> PCB layout from 2013 with dimensions of 78.1mm x 47.3mm, although it isn't
> completely clear what the screenshot is really showing.
>
> Another thing that I wondered about is the width of the board when
> accommodating a board edge connector like the Amphenol 95622-004LF, which
> seems to be a low-cost and readily-available connector. It seems that the
> board edge needs to be less than 50.8mm across because such connectors enclose
> the contact area on each side.

https://cdn.amphenol-icc.com/media/wysiwyg/files/drawing/95622.pdf

that's a really weird connector.  it appears to be a socket, however
it is one that fits on the *edge* of a PCB, of a very specific height
(am having difficulty working that out from the diagram).  it's
probably requiring 1.2mm PCB however that is guess-work.

no wait, Cross Section C, it's 1.5mm, and that also tells us it's the
PCMCIA *header*.

btw, 1.5mm is useless because the clearance on TOP components is
nowhere near enough.


> I am only really asking these questions because I have been looking at making
> some footprints and other resources, and at least the fundamental board
> dimensions should be an obvious thing to discover, but I just didn't see them
> mentioned as prominently as I had thought they would be.

 the PCB has to fit inside the casework, and the casework's *external*
dimensions are required to conform to PCMCIA.

 PCMCIA, is, obviously
(https://www.google.com/search?q=PCMCIA+card+dimensions) 5.0 x 85.6 x
54.0 mm

 however the reason why there's no prominent mention of the *inner*
dimensions is because, obviously, they're critically dependent on what
*casework* is chosen, *NOT* repeat *NOT* on a hard spec.

 it is *PCMCIA case size conformance* that is the hard requirement,
*NOT* the actual PCB size.

 example: the PCB size (its length) will also critically depend on the
PCMCIA header dimensions.  if the header is N mm deep, then obviously,
if you make a PCB that is exactly 85.6 mm long, it will stick out the
end of the PCMCIA casework by N mm, won't it?

 so this is why you don't see "PCB dimensions" mentioned as a fixed
quantity anywhere in the EOMA68 specification, because the PCB
dimensions must be *CALCULATED*, based on the PCMCIA *PARTS* that are
selected for use in production.

l.