[aprssig] Tiny Telemetry

Scott Miller scott at opentrac.org
Tue Aug 31 11:59:15 EDT 2004

> I feel your pain about the calibration issue.  I'm really not sure how I'm
> going to handle that at the moment.  I think the Oww daemon supports an
> offset, and since K1XVM's new Xastir server went online this past week
> (replacing the archaic Sun Ultra 1), there's plenty of capacity to handle
> it there.  I can think of situations where people don't have an urge to
> an entire computer somewhere just to use a cheap weather station.   Maybe
> the price of embedded X86 hardware will come down and open for a variety
> opportunities.

Yeah, what's really a pain about the 1-wire sensors is the fact that if
you've got multiple devices of the same family, you need to know the unique
ID of each so you know which address is which sensor.  For my current 1-wire
weather support, it just assumes that you've only got the basic sensor
package, so it's able to identify all of the chips by family code.  There's
no need to enter IDs or do a learning mode, but that'll change as I add
support for barometers and such.

It's not convenient, but the easiest way I can think of to do it is to just
have a field in the config where you can enter the ID of a sensor in hex.
You'll have to get it from the iButton viewer program or something similar,
which is the inconvenient part, but it should work.  The big advantage over
the current loop setup is that you can have a lot of sensor on the same bus
and only use one I/O pin.

I did some bench testing of the 1-wire code using a standard OpenTracker,
but for my operational unit it was easier to integrate a surface mount
module.  These aren't available for sale yet, and I haven't decided on
pricing, but the existing kits sell for $29, which beats the heck out of
tying up a PC for a simple weather station interface.


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