Tesla Door Phone Decoded (Not That Tesla)

[Danman] has digital door phones manufactured by Tesla — or at least, a Tesla, as they’re not to be confused with the carmaker, though. The problem is if someone comes to the door when no one’s home, there’s no remote indicator. The answer? Reverse engineer the protocol and fix it.

A quick dump on a storage scope showed the data clearly, but it wasn’t obvious what protocol it was using. After a little analysis, it proved the datastream used 4 PWM pulses as symbols with three symbols: one, zero, and stuffing sequence.

Once you can read the bits, it is easy to determine that each frame consists of a 16-bit destination and source address, along with a command byte and a checksum byte. Each station can have an ID from 000 to 999 although you can only dial up to number 323. Some nodes are special, and there are ways to address particular units.

Connecting to the hardware took a transformer for isolation. Honestly, unless you have this exact hardware, this isn’t likely to be something you can directly use. However, it is a great example of how you can figure out a specialized device and bend it to your will.

We love reverse engineering projects. In some cases, it is easier if you have a CT scan.

6 thoughts on “Tesla Door Phone Decoded (Not That Tesla)

  1. I have read many articles about intercom systems. They always seem to have very weird protocols, with leads to ultimate vendor lock-in. My 90-apt building’s entire intercom system including cabling had to be replaced because the main unit was end of life, only 9 years old.

    1. Tesla 2-BUS is intended as a 2 wire replacement of older Tesla analog intercom (read socialist) systems using 4 wires.
      Apartment building in Prague, where I live, used older 4 wire system with many non working phones in flats. Mainly because of cables. Some of four wires were cut somewhere in walls. We replaced it with 2-BUS because we don’t have to do new cabling. Every flat had at least two working wires.

  2. Sounds like a good reason to always run cabling for intercoms in pipes… Well, you should always run all cabling in pipes when hidden!
    Otherwise, it seems like yet another example of the stupidity mankind has such an affinity towards. Not the hack tho, that is great 😃 but the building of stuff that don’t build a better future, only temporary imagined quarterly profits.

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