Re: iButton & Things

[Nigel Orr <Nigel.Orr@xxxxxxx>]

At 14:39 25/05/00 +0100, you wrote:
>connector so that I can monitor temp on a real-time basis. What do I
have to
>do? Do I get some wire and solder the iButtons to it ?? How do I do
that.

There are 2 related technologies.  iButton describes the physical
configuration of the 'litium-battery' sized devices.  They have 2 contacts,
and you connect to them with either an ibutton reader/socket or some other
contact of your design.
1-wire is the actual communications technology (for some reason I thought
it was MicroLAN, they use that occasionally too...), you can get 1-wire
devices that look like transistors, ones that look like surface mount
chips, and ones that look like ibuttons.

You can put any physical type of 1-wire device on the same pair of wires as
any other 1-wire device.  The devices can be permanently connected (which
is probably what you want for temperature measurement) or temporary
connections with an ibutton reader or some other plug-and-socket system
(which you might want if you were using ibuttons for access control).

There are defined ways that a newly connected 1-wire device can use to let
the network controller know that it has been connected, and defined ways
for the controller to interrogate devices on the network to find out who
they are and what they are doing there.

>before I invest in any more iButton but it seems very hard to find any
BASIC
> info on the web regarding iButton.

http://www.ibutton.com/ibuttons/index.html
is probably the best
introduction to ibuttons, and http://www.ibutton.com/csp.html
says a little
about the other 1-wire devices that are available (and they've still got
the free sample offer on, for the tiny devices!)

After that, it seems the best thing to get is the Dallas Semi data book and
CD-ROM, which they'll probably send you for free if you ask nicely (or you
might be able to buy it from RS/Farnell/Maplin).  For some reason, they
don't mention much about the 'bare' 1-wire devices on www.ibutton.com, and
there's not much about them on the www.dalsemi.com site
either.  http://www.dalsemi.com/DocControl/PDFs/pdfindex.html
and search on
the page for '1-Wire' should give you an idea of the products available,
and you can link to their data sheets (just noticed the A/D converter- very
nice!)

And, as ibuttons occupy a place in my to-do list, I can't give you much
more help than that...

Nigel


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