I²C Interface 

The I²C implementation on the Robo TX controller --starting Robo Pro 3.1.3-- is easy to use, especially when an I²C driver is provided, works fine and is reliable.
• WARNING AND DISCLAIMER
This sensor is not part of the fischertechnik system.
Bad connection could damage your TX controller.
Take appropriate precautions.
You do it at your own risks.
Right, the pins of the EXT2 plug of the Robo TX controller, with the safety hole on the left.
Robo Pro side
Arduino side
Sending a command is fairly basic:
Arduino receives the command:

command = Wire.read();

switch (command) {
  case 0x52: // reset
    mySensor.reset();
    Serial.print("< reset");
    Serial.println();
    break;
}
Reading data requires two steps:
  • First step sends the command or the register,
  • Second step retrieve the data.

Requesting directly the data with specifying the register or the command at the same time doesn't work with Arduino.

The two steps approach fixes this issue.
Arduino receives the command:

command = Wire.read();

switch (command) {
  case 0x56: // version
    Serial.println("< version");
    break;
}
Arduino sends the data:

switch (command) {
  case 0x56: // version
    buffer.i16[0] = 0x0208    
    Wire.write(&buffer.i8[0], 2);
    break;
}
Speed with Arduino is limited at 100 kHz.

Learn more about the I²C functions is available at How to Manage an I²C Device?

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