The ASDEX Upgrade tokamak went into operation in 1991 with a proposed lifetime of 10 years. Due
to major modifications ASDEX Upgrade is still in operation. Infrastructure like data acquisition, workstations,
etc. is being modernized, interfaces like RS-232 are vanishing and new interfaces are being
introduced. This leads to the necessity to adapt old hardware. Most of the microcontrollers used in the
old hardware do not offer any support ofthe new interfaces and have to be replaced. A simple and efficient
way is to replace them with open hardware microcontroller boards like the Arduino. These boards are
based on 8-bit RISC microcontrollers and offer a software development environment with a large number
of libraries. In this paper the use of Arduino boards for replacing the position unit, the stub tuner interface
and its use controlling a direct digital synthesizer (DDS) with phase control capability are shown.