[Arm-netbook] GR8 based EOMA68 card

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sun May 21 00:45:30 BST 2017

ismo, hi,

it was just too tempting to have an initial go at converting the
CHIP_PRO_v1 schematic and PCB into a version of an EOMA68-GR8 card,
deliberately cutting it down to the absolute basic minimum - after
only about 6 hours i'm pretty much done connecting everything
together, having cut/paste bits and pieces over:


those are exported from PADS into 9.0 ASCII format if you want to take a look.

importing from ORCAD/Allegro doesn't half make a dog's dinner of
things... *sigh*...

anyway it's the *absolute* absolute bare minimum.  TV-out, gone,
HP/MIC, gone.  OTG, gone.  NAND, gone.  SDC2 is connected to a MicroSD
slot, SDC0 is connected to EOMA68.  SPI2 is connected to EOMA68 so in
theory could also be used as bootable media (factory-install purposes
only).  boot is basically from on-board MicroSD, that can be
over-ridden if people want to by using a Housing MicroSD card (if the
Housing *has* one).

the layout's hilarious: the PCB is over 50% completely empty.  what i
haven't done is:

(1) complete the tracks / connections
(2) add a VCC-3V3 power plane or other power planes.  god did ORCAD
make a mess... *sigh*.
(3) convert any of the 0201 components to 0402 (for goodness sake
don't use 0201 components!)
(4) sort out any tracks as a result of 0201 conversions
(5) re-add the copper pours for the power outputs from the inductors
(to the AXP209).
(6) do a full review to check that the dog's dinner mess made by ORCAD
hasn't split some of the NETs.  PADs doesn't support multi-named nets.
i found one (and joined them) but there may be others.
(7) sync'd PADS schematic and PCB so that a proper NETLIST review could be done.

remember that this *really is* the bare minimum - it'll be amazingly
an under $10 BOM.  also that if you _did_ want to add HP and/or TV-out
and/or MIC sockets, as well as OTG.... you can't: there's not enough
room on the connector, not and have MicroSD as well.  so you can do 3
out of 4 of those connectors but not all.

also bear in mind that there's a couple of tabs on the Litkconn
casework that fit *just* either side of the MicroSD, whch make it damn
awkward to fit the MicroSD anywhere but directly in the middle of the
end of the Card.

also bear in mind that finding mid-mount 2.5in and 3.5in multi-pin
jacks is a complete bitch.  i *might* have one supplier (who speaks
chinese only) who *might* be able to help, there (Runde).

so - what ya wanna do?  do you want to take over this layout/schematic
from here and go with it?  if you leave it as-is it should be easy to
finish within a matter of 2-3 weeks, which means that it's potentially
possible to add to the upcoming (2nd) planned crowdfunding campaign...
or you could run your own.


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