[Arm-netbook] 2.7.4 preproduction sample, 1.7 MD, Questions

Pablo Rath pablo at parobalth.org
Thu Jul 9 11:27:29 BST 2020

On Wed, Jul 08, 2020 at 11:46:49AM +0100, Luke Kenneth Casson Leighton wrote:
> On Tue, Jun 16, 2020 at 9:45 AM Pablo Rath <pablo at parobalth.org> wrote:
> >
> > I have recieved an EOMA68-A20 2.7.4 preproduction computer card and the 1.7
> > micro desktop (MD) last week. Just for clarification these boards are nothing new
> > and have been discussed on this mailing list.
> > If some of you already have their preproduction boards ready, I would
> > appreciate any help, hints and suggestions to help me getting started.
> >
> > Altough I have some experience with handling arm-boards I am now afraid to do something
> > **stupid** and break/fry the boards.
> > After some digging in the list-archives I found this thread ([1]) where Richard and
> > Luke discuss how to connect the bare computer card with the bare micro
> > desktop.
> > I have many questions:
> > 1. Connecting computer card and micro desktop:
> > I am aware of the photos attached to [2].
> > Does the mentioned video exist?
> no.
> > Richard, did you send photos to Luke? (If yes, can I have them?)
> > Luke, do you want me to send you photos too before apllying power?
> yes that would be good.  visually it is pretty obvious.  just do *not*
> bend or waggle the Card as it's inserted (however you may find that
> the connector is soldered at a slight angle of 1 to 3 degrees).
> from visual inspection from the top, the gap left and right should be
> equal.  this should be logically fairly obvious.

Images can be found here (I could not upload them to the rhombus-tech
wiki becaus a virus checker is not defined):

> from visual inspection from the front, it should also be obvious if
> the card has been inserted where the top row of pins has gone into the
> bottom part of the connector or vice-versa.

Visual inspection from the front looks good to me but is difficult to
photograph with good light and correct focus. 

> If You Can See Pins You Got It Wrong.

I can't see pins anymore.
> also, once inserted, place the anti-static bag *in between* the Card
> and the MicroDesktop PCB.

Is this for anti-static purpose or to add a bit of stability? Do you
fold your bag to fit the entire length of computer-card?

> >
> > 2. PSU for micro desktop:
> > According to the mentioned thread ([1]): "5.5mm jack with a 2.1mm centre hole, middle is
> > +ve (aka "pin positive")", "Anywhere between 7 and 21v is fine, minimum 1A, 1 5A is better"
> >
> > So I searched for a DC PSU in my household and read Wikipedia where it is
> > mentioned that OD 5.5 mm / ID 2.1 mm is common on guitar effect pedals but my
> > multi guitar effect pedal PSU did not fit (ID too small). Finally I found a
> > matching DC PSU from a low volatage guitar amp. It says O / P: DC 15V, 2A and a symbol (positive polarity):
> > L. P. S.
> > - -(.- +
> you're better off checking with a multimeter.  it's pretty standard
> (pin positive) however there is no substitute for actually checking.
> i.e.: don't guess - check.  hardware is unforgiving.
Bought a multimeter and checked. DC PSU is good to go.

> > Should we document this somewhere on rhombus-tech.net?
> yes, good idea.

Will do it in next couple of days. 

> > 4. SD-card ready / U-Boot
> > Tried to compile u-boot-sunxi [4] and make exits with "System not configured".
> > So Luke, what did you use as config
> it's on the wiki somewhere.  it has been 5 years so i will be
> searching just as much as you would be.


> > or has something changed over the years?
> no.

> > 5. Git, notes and documentation
> > Finally I am wondering where to put my notes. A subpage on rhombus-tech seems like a good idea
> > good to me
> yes.

After a quick check it seems one can not create subpages from the online
editor (only edit pages). 
Can I still send you an ssh-key to get a better access to the wiki?

> > and indicates a work in progress in contrast to the various wikis
> > out there. Where do you want me to push my work in progress git branches if I
> > manage to hack something useful together?
> i never needed to make any modifications to any linux kernel or u-boot
> source code, so one has not been set up.

Ok. Thanks. 

kind regards 

More information about the arm-netbook mailing list