Com port dropped when switched to analog mode sdc2130

I am trying to run the sdc2130 controller off of a pot. when i run roborun+ i am able to run the motor through the serial but when i mute the serial to switch to using the pot the computer says it can not recognize and drops the connection. As a bonus I am planning replacing the pot with an arduino if maybe there is a better way to go about this thank you for your help