Well I thought it’s going to be easy, not! Never before I soldered anything this big, the rule of soldering is that both material to be soldered are at soldering temperature. Soldering without heating the busbar first is impossible, as if there is a layer on the copper that resists soldering.
A video on youtube showed that he had to heat the busbar up in the oven first before soldering. Not having oven handy, the 20W soldering gun was rested on the bar to heat it up to soldering temperature. Busbar dimension is 300mmx40mmx5mm and it took about 25mins to heat it up. Then soldering can begin.
The drive-by-wire pedal is from a 2004 R53 Mini and electrically the same with pedal used in E46. So the schematic can be attained from WDS. Not having the proper connector, wires are soldered directly to the pedal.
The pedal is powered by 5V DC, there are two potentiometers inside and output of one of the terminal is half of the other. The microcontroller should be able to read the input and verify before driving the motor. A fault condition (voltage not half of the other) would cancel power to motor.