Date: Sun, 21 May 2017 00:45:30 +0100 From: Luke Kenneth Casson Leighton lkcl@lkcl.net To: Eco-Concscious Computing arm-netbook@lists.phcomp.co.uk Subject: Re: [Arm-netbook] GR8 based EOMA68 card Message-ID: <CAPweEDywhR-LUBAZojgGr2Hn0WJijOuZayxvJBK4W DH7MuhRDw@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 work.
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 use. 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