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What The Nest Learning Thermostat and Critical Link Have in Common

As an engineer, I’m always interested in tear-downs – dismantling a machine, a gadget, a device to see what’s in its innards. Most engineers, I suspect, start doing this when they’re kids. We want to know how things work – the clock, the motor, the radio – which is how we end up becoming engineers. Since so many items now are electronics-based, rather than mechanical, things look different on the inside than they did in the good old days.  But it’s still plenty interesting.

One of the tear-downs that I particularly enjoyed actually happened over a year ago, and that was of a Nest thermostat. (Here’s the article by Sam Sheffer, which was on The Verge in late December 2011.)

For those who aren’t familiar with the Nest, it’s a “Learning Thermostat” which you don’t need to program to schedule when our HVAC clicks on and off. It learns your habits – when you get home from work and turn up the heat or turn on the AC, what temperatures you set and when, and programs itself. It’s also got WiFi so can be controlled from your iPhone. All this is good for the environment and the pocketbook, eliminating the waste of having the heat running when no one’s home and saving on your heating and cooling bills.

Anyway, what they found inside the Nest was a Texas Instruments ARM Cortex A8, the processor that makes the Nest so smart.

I found this pretty interesting, because our MitySOM-335x is also based on an ARM Cortex A8. It’s not the same one – they use an AM3703, ours is the AM335x family. Our choice was motivated by its fit with our target market, which includes everything from laboratory and medical equipment to test and measurement devices.  These are applications that sometimes require industrial protocols like CAN and PROFIBUS, but more importantly always require Ethernet. The AM335x features dual gigabit Ethernet interfaces, where the AM3703 does not support wired Ethernet.

The AM3703 may be processing overkill for the Nest smart thermostat. All things considered, I suspect that Nest went with the AM3703 because the AM335x may not have been available at the time they were doing their development. The AM335x is available at lower speed grades than the AM3703, so Nest could have gotten a good processor a lower price point – a processor still fully capable of doing what the Nest needs doing. At least for now. Nest may have other capabilities in store for it. I certainly hope so – I just put one in my home and love new features!

Anyway, I really do like to read about tear-downs (and even to do my own every once in a while).