Also see: en/TowerPro25A2Regler

Converting TowerPro 50A ESCs to TWI/I2C

Changes needed

To convert a TowerPro 50A ESC to allow it to be controled over the I2C (TWI) interface by the flight controler you have to cut two connections on the PCB, to separate a resistor network from the SDA pin, and reconnect the network of three resistors to a different processor pin. In addition you can cut a third connection to free up the orange PWM wire for the servo lead so that you can use the existing servo lead as I2C/TWI cable with an additional GND wire.

Step by step conversion in pictures
One side of a new TowerPro 50A ESC.
Other side of a new TowerPro 50A ESC.
Fully unpacked new TowerPro 50A ESC.
Fully unpacking is not a good idea as the heatsink is held in place with cream and will start sliding, so you will have to tape it in place temporarily.
This is a simpler way of keeping the heatsink in place while converting the ESC.
First part of the conversion completed with the resistor network reconnected to a different processor pin
SDA and SCL pins connected to the red and orange servo leads after cutting the old connection to the orange lead. As far as I can tell at the moment the red servo wire is not connected to anything (these ESCs do not have a BEC).
Programming adapter soldered to the MISO, MOSI, SCK, RST, and GND, and temporary connectors for battery and motor in place, ready for reprogramming and testing.
Close up of the temporary programming connections. I-ve found quickly soldering the wires to the pins or resistors or pads, is as quick as using a programming adapter made from Fimo clay as those tends to be a less then 100% perfect fit.

Final steps in the conversion

Next step is to reprogram the processor, test the ESC with a flight controler and an old motor to ensure the reprogramming went well and the ESC is correctly translating I2C/TWI throttle settings into motor RPMs, remove the temporary programmer wiring, epoxy all other new wiring in place to avoid breaks or shorting out of any wiring, and re-heat-shrink the ESC.

/!\ ToDo: hier gibt es noch etwas zu tun