[clug] Linux compatible external Thermometer

Peter Barker pbarker at barker.dropbear.id.au
Tue Feb 23 13:45:25 MST 2010

On Tue, 23 Feb 2010, Kevin Pulo wrote:

>> Unfortunately, they never appear to have a serial number, so there's no
>> *absolutely* reliable way to ensure you don't get multiple devices out of
>> order on the one machine.
> Hmmm...  What about if they went onto separate USB host controllers,
> so that you could have a script which pokes around in /sys to figure
> out which is connected where?

Yep, if y our system is static software and hardware-wise, that will be 
OK.  Problems happen if you:
  - add a hub
  - change kernels (rarely! - who remembers the Great Device Renaming a 
few years ago?)
  - need to do some work on the server, and just yank everything without 
labelling them first

> I'm also interested in these things - what driver do you use, and how
> do you read the data out of them?

They actually come in a variety of flavours.  The old ones produced a 
/dev/ttyUSB device - mine doesn't.

The one I'm using at home I use a package called "temper-1.0" to read. 
Simple C program which uses libusb to get the data.  You should be able to 
google for that package.

I modified the C program such that it simply spat out the answer.  Wrote a 
perl wrapper suitable for use by snmpd.  Modified the snmpd config to use 
that wrapper.  Used "cacti" (a pre-existing asset in my setup) to graph 
the data.

> Kev.

Peter Barker                          |   Programmer,Sysadmin,Geek.
pbarker at barker.dropbear.id.au	      |   You need a bigger hammer.
:: It's a hack! Expect underscores! - Nigel Williams

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