Thenks for your response.
I got the encoder working using a pull up resistor.
But now, after a couple of days working fine I suddenly get a somehow strange behaviour.
For some reason the encoder counts are counting up itself rapidly as soon as the roboclaw is under power. when I turn the rotary encoder manually this will influence the count-up in a way that it slow down or accelerates the counts depending on which direction i turn the rotary encoder to.
When I suddenly turn the encoder very fast about 180 degree or so, the counting-up stops for some seconds before it starts again.
I guess, something is broken there, right?
Do you have any experience with this behaviour?