[time-nuts] RPi/ beagle bone-like computer without video

Attila Kinali attila at kinali.ch
Fri Dec 2 11:51:07 EST 2016

On Fri, 2 Dec 2016 08:05:17 -0800
jimlux <jimlux at earthlink.net> wrote:

> > I'm measuring 0.350A with max cpu usage on all cores and the following
> > settings:
> >
> @ 5V, right, so 1.75W going full out.  That's a useful number to know.

I once did an board with an i.m233 (arm9 at 400MHz) and it did less
than 0.5W IIRC. But I think this is about the lower you can do without
tweaking the OS.

> > Apart from that I read somewhere that the beaglebones have terrible EM
> > characteristics. But I can't find my source so take it with a grain of
> > salt :-)

Yes. The BBB is badly designed in this regard... The RPI is better there.

> I must say, there are more of these things available in almost too wide 
> a variety.. You could spend days going through all the datasheets and 
> websites - I suspect that they ALL have about the same power consumption 
> for a given amount of processing horsepower - same feature size on the 
> die, after all - so it's more about peripherals and ease of use

There are way too many, IMHO. And a lot of them are not usefull for
a lot of stuff or have very bad support. The Odroid are a prime example
of this. There is a "community" around them, yet getting them to do
anything usefull is a major pain. There is a handfull of companies
I know of, who do provide good support and those are the ones I am
usually sticking to (unless I have special needs).

> And, it's more likely that idiosyncracies in the distros have been 
> identified and it's more likely that the software will run on them after 
> its built.

It's actually better to go with a company who is invested in giving
you a working board than using something popular. Especially one that
cares to push all its patches upstream.

Beside the mentioned Toradex, and Aries Embedded, there is also Olimex
which is known for it's wide variety of boards with good support.
Depending on your exact requirements, I would probably go for one of
the i.mx233 boards (the imx233 nano is quite neat) or A10 or A33 board.
Especially the i.mx233 is nice as it has an on-chip Li-poly charger/controller.
All you need to do is to supply it with 5V and it does the rest.

A note of warning: a lot of the boards from Olimex have not enough ground
pins for the high speed singals they provide. If you are transfering data
with high-speed (several 10MHz) over the headerpin connectors, you will need
to add some additional ground connections.

What are the exact requirements you have? How much computational power
do you need? How do you interface the sensors? How many boards will
you need? Is it out of question to build your own processor board using
one of the ARM9's in QFP? What is your budget?

The reason why I'm asking the last two questions is, it is often more efficient
to do your own CPU board if you have to design a PCB anyways for the sensors,
need more than 10-20 boards and you can live with one of the "small" ARM9's
that come in QFP packages (like the i.mx233 or AM1705).

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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