On Fri, May 31, 2019 at 3:47 PM Paul Boddie paul@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.