TempTale Direct Teardown

Written 2017-04-05

Tags:STM32 Teardown flash ARM 

A Handy Shipping Watchdog

Ever wonder if your kobe beef shipped quickly enough? If your suspicous neighbor popped the lid on your coolerful of science experiment? Some other, simple, zany reason? TempTale makes a line of very handy environmental monitors. Drop one in when a sensitive shipment is packed, and the receipient can quickly verify that the package temperature was maintained through the shipment by opening an automatically generated PDF file on the device. The device appears as a USB mass storage device with a single PDF file onboard.

But, how does it work?

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Internally, it consists of an STM32 ARM microcontroller, external serial flash, a coin cell battery with solder terminals, some buttons, a high-speed and low-speed oscillator, and a bare LCD panel.

The bare LCD is neat, as the static discharge on my fingers caused a shimmer of pixels when I first touched it. Also, pay attention to the front edge below: The glass has metal contacts that then touch thin metal sheets embedded in the thick white-faced foam strip at the front. Contact is held in by the case and pcb.

TempTale direct teardown

Software-wise, only a few components are needed for something like this. A USB mass-storage driver, a filesystem driver, a PDF writer, and some custom logic to wake up the CPU from a low-power event, likely the RTC alarm, read the temperature, and store it to a circular buffer. Just before USB enumeration, write the circular buffer into a PDF file. Possible example components are linked above.

These are really handy little devices, I hope they become more widely deployed in the future for shipment validation. Sensitech even makes models with GPS and accelerometers as well.