Reverse engineering the Essent E-thermostaat

Keep your hands of our code

If you have the same interests as me, then you can probably relate the way these programming sessions go; one succes after another, you keep coding and trying hours after hours and once you stumble accross a setback, you can’t get your head around how this could have gone wrong? How can this result not be what I expected it to be? Taking a step back, literally, often shines a new light on your problem.

So I made myself a cup of tea and then I suddenly realised I have seen this behaviour before. Code protection. It is a thing. Often these microchips have some bits you can set after testing so no one is able to steal your code of the chip. So I retreived the code protection bits and I confirmed my worst nightmare at that moment: this chip was code protected. No easy way to get code from this chip. If you want to reset these bits, you have to erase the whole chip, but that would defeat the purpose of what I was trying to achieve: getting the firmware in the first place before writing to the chip.

4 Replies to “Reverse engineering the Essent E-thermostaat”

  1. Enjoyed reading your article, too bad you didn’t succeed.
    I will check back later to see if you see if any progress has been made.
    In the worst case,. I have disposed of my e-thermostaat and help is too late for me

    1. Thanks for your response. For now I paid the 24 Euros so I can use the thermostat for at least another year. So probably no updates from my side, but if so I’ll let you know.

  2. Maybe it is possible to read the thermostat thermometer and rig the + and – button so you can control it with an Arduino or Pi Zero? Or even a step further, connect said Arduino or Pi to read the data that is going to the LCD?

    1. That’s probably feasible, however I doubt if that would be much less work than designing my own thermostat and letting my home automation system control it. If you already go the extra mile to get an additional device such as Arduino or Pi to read the pins, switching a relay and reading a temperature sensor is not that much work either though.

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