[Arm-netbook] Release of SoM board KiCAD files with 2x100 pin ARM as a stepping stone

[jm]

On Mon, 2012-12-10 at 14:57 +0000, luke.leighton wrote:
> On Mon, Dec 10, 2012 at 2:48 PM, jm <joem at martindale-electric.co.uk> wrote:
> > Hi,
> >
> > I'm releasing SoM board KiCAD files with 2x100 pin ARM as a stepping
> > stone for eventually building the A10 on to SO-DIMM module.
> > http://www.gplsquared.com/SoM1/SoM1.html
> 
>  awesome!
> 
> > The next target is an A10 SoM board.
> > You can send me updates to get a board for A10 built
> > if you feel generous and want to share KiCAD design files.
> 
>  yes!  http://git.hands.com/?p=eoma.git;a=blob;f=pcb/allwinner_a10/library/allwinner.lib
> 
>  the only reason i haven't tackled this is because KiCAD can't handle
> those wiggly-lines to make the DDR3 balanced-line pairs of the exact
> required / specified length.
> 
>  they also need to be a very specific ohms value and i haven't the
> knowledge to do that either.
> 
>  otherwise i would have started on the PCB layout, using KiCAD,
> like... a year ago.


1. Luke, I have pinout of BGA for A10
http://www.gplsquared.com/SoM2/SoM2.html
but it is not accurate. Many of the NC pins have functions when I check
against Cubies design, you design and Wits design. I'm not lost, but we
need a full BGA chip pinout diagram to avoid getting lost. I can reverse
engineer from all the different drawings - but if someone has it
already, share it please!!

2. The wiggly lines issue. Personally I believe utter cretins are
stitching up everybody with this one. I have university degree in
electronics and I just don't believe any of it because it doesn't agree
with any of my training of high speed electronics.
So what I propose is that I design the layout as it should be done.
I have budget for several iterations to get it right.
And I'm pretty sure its a non issue - so I am going to design it the way
my training says it should be designed,
document it, build it, test it and if it don't work, then OK we need
wiggly lines, but if not, it can be buried for good.
:-)

3. The ohms thing is relevant but lots of ways to mitigate it - KiCAD
the latest edition has calculator for that. Also, some issues can be
taken care of with some resistor tweaks if designed properly. (If not
designed correctly - no amount of tweaking will work.)