[Arm-netbook] arm-netbook Digest, Vol 82, Issue 47

Ismo Väänänen ismo.vaananen at gmail.com
Tue May 23 14:25:08 BST 2017

> Date: Sun, 21 May 2017 00:45:30 +0100
> From: Luke Kenneth Casson Leighton <lkcl at lkcl.net>
> To: Eco-Concscious Computing <arm-netbook at lists.phcomp.co.uk>
> Subject: Re: [Arm-netbook] GR8 based EOMA68 card
> Message-ID:
>         <CAPweEDywhR-LUBAZojgGr2Hn0WJijOuZayxvJBK4W
> DH7MuhRDw at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
> 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:
> http://hands.com/~lkcl/eoma/gr8/
> those are exported from PADS into 9.0 ASCII format if you want to take a
> look.

Sweet, thanks. Just imported these to Altium.
Actually noticed that the Allegro .brd import in to Altium needs Allegro
installed to function.
The imported layout looks like this: https://i.imgur.com/uPmEsQb.png

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

It so does. None of the component parameters for the passives carried over
in the import.
The component values imported as separate strings for the passives, at
least the cases are OK.
Of course, the mentioned cases don't exist. So that needs some additional

> 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).

That's OK with me. More space to use for potential future expansion.

> 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

Ya 0402 is a lot more sane to deal with than 0201.

> (5) re-add the copper pours for the power outputs from the inductors
> (to the AXP209).

This and in general figure out the power stuff.

> (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.

It's gona be FUN mating the CHIP Pro schematic files with that layout.
Absolute joy.

> 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.

I'll fully decide on this later on, USB+Video would allow for standalone
And sort-of usable while standalone is aligned with the spirit of the
EOMA68 standard (or how I see it at least).

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.

Where can I find datasheets, drawings or 3d models for the Litckonn cases?
Can I buy a few sample units from somewhere for fiddling around?

> 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).

I'm perfectly OK with deleting the sound input/output.
Just a shame to leave the sound hardware unused when it exists.

> 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.

More or less regardless of crowdfunding or anything I'll continue doing
work on my vision of what a GR8 based EOMA68 card would be.
But my progress won't be fast as I'm working full time and doing the same
stuff at home as I do at work is not attractive every single day.
A low cost alternative for low powered embedded applications might also be
attractive to some folks and in general for testing and debugging housings.

On an other note, replying to this list while it's in digest mode is a bit
weird. I might have to change it from digest to the individual message
style and hope that gmail is good enough at clumping the threads.

-Ismo / 2ftg
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