Thanks for your help. It is working now. I needed a level shifter and some pullup resistors for the decice.

The RPIi is a 3.3V device, your device 5V. What pull up resistors are attached? The RPi has pullups, your device may or may not have pull ups. To strong pull ups are dangerous to the RPi btw. Bidirectional level convertors exist for I2C and also may have (optional) pullup resitors. With the USB I2C...

I know about the ground, i only forgott to mention that
My device is powered by an external powersupply as my stepper needs 10V.

Thx hansotten, i haven't thought about the 3.3 V

I used 2 wires to connect it to the scl and sca (3 and 5) port of the pi.
There is a jumper to set to address to 192 or 194.
If i use my windows i2c to usb tool it is possible to control the driver, but my pi does not show any connected device if i attach it to it.

Hi, I'm new to the I2C programming. I bought this stepper driver module ( http://www.elv.de/output/controller.aspx?cid=74&detail=10&detail2=30930 ) I then followed the instructions to enable i2c on my raspberry. ( https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c ...