[davb]

Can anyone recommend any resources on power management on something like this?

My background in electronics is quite basic though I'd love to understand how they managed to build an ARM-based, battery-powered device that is predicted to last for years. I know it's not "always on" but it's fascinating nonetheless and I think building something similar would make for a fun project.

[steckerbrett]

Most microcontrollers have extremely low power sleep states, maintaining interrupts on external inputs often only draws the smallest amounts of power. When you're designing for low power electronics like this you often run into the problem of the self discharge of the battery completely dwarfing any consumption your microcontroller has. I'm reasonably confident they chose a lithium AAA simply because they have very low self discharge, and a AAA over something like a coin cell due to the rather enormous amount of power needed to transmit 802.11.

I get the feeling that this device is pretty tentative for Amazon, they haven't gone to huge lengths to keep the price of the build down. In particular there's also a connector on the bottom right of the PCB that looks a lot like it could be for a small screen or some other peripheral.

[TickleSteve]

The main loop looks something like this: Note that the button is hooked up to an interrupt to wake the processor and return from the Sleep() fn.

  main()
    while true
      Sleep();
      InitialiseNetworkStack();
      SendPacketToAmazon();

[minthd]

Basically it always sleeps, and wakes only when you press the button - does it job rapidly and goes back to sleep.

Since you rarely press the button , it can live for years.