Diagnosis in a Complex World

Submitted by WardCunningham on Sat, 2012-01-21 20:45

After two years of service my outdoor air temperature sensor blinked out last week. Moisture was the culprit as shown here:

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Various readouts in my SensorServer system lead me straight to the problem through a half-dozen layers of software. How cool is that?

Honestly, I'm more interested in how we know and trust complex measurements than knowing the temperature outside.

My SensorServer software worked so well that I prepared a Keynote presentation explaining each diagnostic step along the way. I meant to post it here, but damn, low battery led Keynote to throw away my presentation. That makes Apple the weak link, no?

I see a lot of broken systems in our future. A robust world will depend more on diagnosis and recovery than on the out-of-the-box usability that has made Apple famous.

The data sheet for the device at http://datasheets.maxim-ic.com/en/ds/DS2482-800.pdf There is also an arduino library for the ds2482 at https://github.com/paeaetech/paeae.

I am pleased that not only does it bus isolation and the ability to detect shorts, but it also cuts out bitbanging the bus in software. I was especially happy to be able to initiate the readings in parallel and read them back later in relatively clean way. The sample code for the Arduino Library has been mangled (by html filtering), and is unusable. So I have attached one that works and also reads the temp sensors here (http://dorkbotpdx.org/files/ds2482.tgz)