Reverse engineering the Tesla 2-Bus protocol #ReverseEngineering @danmaneu
Daniel Kucera on Danman’s Blog posts about reverse engineering digital door phones by Tesla (the phone company, not the car company) which utilize a proprietary two wire protocol.
I wanted to be notified when someone rings when we are not at home so I decided to reverse engineer it.
During idle, there is a voltage of about 23V which is there to power the phones as they don’t have any other power supply; during a call, the voltage drops to about 12,6V and current goes to 47mA. So I took my scope and started to measure the signal. In short, I have found, that there is some sort of digital signal and analog voice modulated on top of the DC component (timeframe of one call).
The data is encoded using symbols consisting of 4 PWM pulses. There are 3 symbols – logical 0, logical 1 and stuffing (‘-‘). Each frame starts with several dozens of stuffing symbols. Then bit symbols are sent each one followed by one stuffing symbol. On the picture above, “A” marks the start of 1 then follows: -, 1, -, 0, -, 0, … Each frame consists of 48 bits where the last 8 bits are checksum.
An Orange Pi is used to decode the signals.
You can read the details in the post here and see the software on GitHub.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.
