Kindle Gets Downgraded to an Expensive Thermostat

Kindle thermometer

E-readers are awesome, don’t get us wrong — but if you have an old one collecting dust, why not use it for something? [John] decided to hack his old Kindle  to act like a thermometer!

The Kindle’s Linux OS is re-purposed to use the Freescale CPU’s internal temperature sensor as a thermometer — since it’s not doing anything most the time, it should be relatively accurate of the ambient temperature.

Unlike some of [John's] earlier hacks, this one is completely self-contained and reversible. In fact, it’s just a few scripts that check the temperature every minute and then display it in large digits on the screen. The buttons allow you to convert units or reverse boot to the original Kindle software. It can even graph the recent temperature! It makes for a very easy to read outdoor thermometer.

And not to waste all of its hardware features, [John] also set it up to act as a web server, sending the temperature data via port 8014.

You could also take it a step further and have a full weather station, in a nice wooden frame.

Comments

  1. franklyn says:

    How did he program the damned thing ?

    • john says:

      The Kindle is ‘jailbroken’ — basically you can get access to the Linux OS internally in it. The thermometer program(s) then just stop the book display program, take over the display and with a combination of shell scripts and awk programs display the temperature.

  2. cpldcpu says:

    Why is the text not centered! Why oh why?

  3. Matthias_H says:

    A thermometer. It would be a thermostat if he controlled the CPU activity in order for the system to reach a set temperature.

  4. vonskippy says:

    “it should be relatively accurate of the ambient temperature.”

    And was that guess checked? Seems like the system will always be at least a few degrees higher then ambient.

    • carbohydrates says:

      You forgot to include the first part of the quote;

      “since it’s not doing anything most the time, ”

      With this program, the CPU only does several computations *per minute*. 12 updates of the dots on the bottom of the screen, and a few to poll and display the temperature.

      That’s pretty much 0% CPU load, it’s likely to be close enough.

      • john says:

        The CPU load is quite light. The sensor is not perfect (different Kindles give different results), and the code has an option to subtract out a fixed error — either from the sensor itself, or self-heating.

  5. strider_mt2k says:

    I have to agree the thermostat thing is bush league.

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