Subject: Minimal ARM-Linux board?

From: Ansel Sermersheim <[email-masked]>
Date: 31 Aug 1998 21:20:17 -0700

I'm interested in finding out what the minimal configuration is that
ARM-Linux can cope with.  I envision something with just a CPU, some
ram, serial ports, and a hard drive controller on a breadboard.

I recall conversing with someone who had done this.  Is there anyone
out there who can give me any leads on how hard this would be to do?
I'm not afraid of getting my hands dirty.

(Eventually, I'd like to be able to make a wearable computer out of
the ARM; its power requirements are wonderful compared to Intel
chips.)

Thanks,
-Ansel
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From: Dave Gilbert <[email-masked]>
Date: Tue, 1 Sep 1998 21:10:43 +0100 (BST)

> ram, serial ports, and a hard drive controller on a breadboard.

I thought you said minimal :-) CPU, RAM, a ROM to boot from and preferably
a file system; be it in ROM, battery-backed RAM, or PCMCIA card or
network connection what have you.

> the ARM; its power requirements are wonderful compared to Intel

I suggest you look at the SA-1100 or the ARM7110 (?).  Dave > 

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From: Philip Blundell <[email-masked]>
Date: Tue, 01 Sep 1998 21:38:47 +0100

>ram, serial ports, and a hard drive controller on a breadboard.

Well, theoretically just a CPU, some RAM and some way to get the kernel there
is all you need -- but it would be hard to make it *do* very much.  It all 
depends what you're trying to achieve.

p.

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From: James Craig <[email-masked]>
Date: Tue, 1 Sep 1998 23:40:49 +0100 (BST)

> depends what you're trying to achieve.
One dumb question. Breadboards are, by and large, DIL. Where on earth do
you get a breadboard that can actually physically accomodate an ARM???
If you can get one cheap, I want it. :)

--
James Craig <[email-masked]>
            <[email-masked]>

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From: David Alan Gilbert <[email-masked]>
Date: Wed, 02 Sep 1998 10:15:01 +0100

> If you can get one cheap, I want it. :)

I've seen a couple of times little PCB's padded out for an ARM taken to
0.1 spaced pins (albeit in a patttern unsuitable for a breadboard);
a similar little PCB would do the trick.

....Then you just need someone very good with solderpaste....

Dave

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From: Hugo Fiennes <[email-masked]>
Date: Wed, 2 Sep 1998 11:26:09 +0100 (BST)

> If you can get one cheap, I want it. :)

At warwick uni I did an ARM7100, wirewrap. Admittedly, we had to make a
PCB to get the 208 pin TQFP (.5mm pin spacing) out to 0.1" pingrid,
and there was some interesting faffing to get a 72-pin SIMM socket onto
0.1" grid (it's 0.05" staggered), but it all worked (and still does).
A while back I got 2.0.33 up on it: no hdd, but it has ethernet and so has
NFS root (and no swap...). The 7100 is a 3.3v part, but is fine at 5v,
which makes things easier! As for ease of use: it boots from an 8-bit ROM,
has loads of I/O, 1 serial, and is glueless to DRAM and the ROM.

See http://www.dcs.warwick.ac.uk/~altman/camera/ : if you want more techie
details I can email you the .pdf of the project report, and if it's for
something educational, I expect I could probably persuade warwick uni to
part with one of the other '7100 mounting pcbs (they had about 5 made,
but we only used one). You'll need some SMT gear to put the chip on, though,
or be very brave.

Hugo

-- 
Disclaimer: "The contents of this albatross were measured by weight, not
volume. Contents may have settled during transit."

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From: David Alan Gilbert <[email-masked]>
Date: Wed, 02 Sep 1998 12:57:31 +0100

> has loads of I/O, 1 serial, and is glueless to DRAM and the ROM.

How did you get hold of 1 ARM7100 ? I can imagine many companies being
happy to supply a couple of thousand; but 1 is often difficult?

> but we only used one). You'll need some SMT gear to put the chip on, though,

If you/Warwick are OK about copyright then it would be nice to put it on the
web somewhere.

Dave

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From: Philip Blundell <[email-masked]>
Date: Wed, 02 Sep 1998 13:05:24 +0100

>happy to supply a couple of thousand; but 1 is often difficult?

You can often get them just by asking distributors for samples.  Sometimes you 
have to fib a bit and say that you're planning to buy a billion of them in a 
month's time or something but they usually oblige.

p.

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From: Hugo Fiennes <[email-masked]>
Date: Wed, 2 Sep 1998 13:11:41 +0100 (BST)

> a similar little PCB would do the trick.

(see my last message: the PCB we did expanded the pin layout to about 4"
square, meaning the pins were logically arranged and far apart enough not
to confuse too much :-) ).

> ....Then you just need someone very good with solderpaste....

It can be done with a fine tipped soldering iron and some soldering braid.
Patrick just did this with a SA1100. Ok, so we had to spend 4 hours with
a microscope afterwards checking the joints (no joke!) but it worked :-)

Hugo

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From: James Craig <[email-masked]>
Date: Wed, 2 Sep 1998 19:16:46 +0100 (BST)

> a similar little PCB would do the trick.
I've seen PLCC adapters that *do* give you a DIL socket but they're meant
for fairly small numbers of pins - say a 28 pin EPROM. I could manage to
solder/plug in the chip easy enough but I've never seen one big
enough/sensibly enough sized compared to a normal breadboard to take an
ARM.
> ....Then you just need someone very good with solderpaste.... > 
I can do that. :)

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From: Ansel Sermersheim <[email-masked]>
Date: 07 Sep 1998 16:13:57 -0700

>>>>> "Hugo" == Hugo Fiennes <[email-masked]> writes:

>> I've seen a couple of times little PCB's padded out for an ARM
>> taken to 0.1 spaced pins (albeit in a patttern unsuitable for a
>> breadboard); a similar little PCB would do the trick.

> (see my last message: the PCB we did expanded the pin layout to
> about 4" square, meaning the pins were logically arranged and far
> apart enough not to confuse too much :-) ).

In browsing today, I found a QFP-to-PGA board.  Can anybody confirm
whether it would work with an ARM?

It can be found as P.N. 96-208M50 on the top-middle of p 119 in the
July-Sept 1998 DigiKey catalog.

Once you have it out to PGA it should be a lot easier to deal with.

These little guys aren't cheap ($51 in singles, $44 in 25+) but it's
not insane like some QFP sockets.

-Ansel
-- 
I used to be convinced that MicroSquish shipped crap because they simply
didn't give a flying fuck as long as the sheep kept buying their shit.
Now, I'm convinced that they really do ship the best products they are
capable of writing, and *that's* tragic.
   - John C. Randolph, about MS quality control.

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From: Hugo Fiennes <[email-masked]>
Date: Tue, 8 Sep 1998 09:58:32 +0100 (BST)

> whether it would work with an ARM?

They *should* do, but remember you don't get a groundplane on these,
as they're completely generic, and you can't mount decoupling close to
the chip. Worth a try, though. I've used them for smaller chips, eg
ethernet, and they work. www.wilmslow.co.uk (I think) also do them, sold
by RS (http://rswww.com - strange address...)

Hugo

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From: Paul Koning <[email-masked]>
Date: Tue, 8 Sep 1998 12:22:28 -0400

> whether it would work with an ARM?

Be careful.  There's PQFP, MQFP, TQFP... lots of "xxxQFP" packages of
varying sizes.  For any given pin count you might find several, the
main difference being lead pitch.  Check the package specs of the chip 
you want to hook up to see if there's a matching converter.

	paul

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From: [email-masked] (Theo Markettos)
Date: Tue, 08 Sep 1998 23:17:06 +0100

> > apart enough not to confuse too much :-) ).

If you're brave, you can build the equivalent of one of these boards, by just
taking some cheap plain matrix board (like stripboard but without the
strips - something like 3UKP per square foot), sticking pins into it and
soldering wire-wrap wires between them and the chip pins.  I've done it to a
100 pin QFP, with 0.65mm pitch 0.3mm wide leads.  It's doable - I had to make
a custom iron bit out of a thin piece of wire, which dissipated so much heat
that lots of solder on the 25W iron end was needed to keep it up to
temperature.  It also takes _ages_, but if you don't have PCB production
facilities it's the only way of doing it with bits lying around.  The EMC and
electrical properties of such an assembly are probably dire, but it works.

> whether it would work with an ARM?

I don't see why not.  One thing to be careful of is to make the distinction
between EIAJ and JEDEC QFPs - they have the same name but sometimes
a different layout.  IIRC I'm using an EIAJ 100 pin QFP which has a 20x30
pinout, while I think the JEDEC version has a 25x25 pinout.

Other places to try are Aries (www.aries.com IIRC) and Yakamichi (spelt
wrongly).  I tried Aries' UK distributor for the above 100 pin EIAJ QFP-PGA
adaptor - they had it, but with a minimum order of 2 at something like 50 UKP
each, and a lead time of 14 weeks from the States.  Needless to say I didn't
take them up on that...

If anyone's interested, there was a bit of discussion on this on either
comp.sys.arm or alt.comp.hardware.homebuilt a while back which might help
(IIRC it was someone wanting a socket for a SA1100).  Try Dejanews...

-- 
Theo Markettos          [email-masked]
Liphook
Hampshire               Web site, including Acorn backup software
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