Open source hard- and software: Using Arduino boards to keep old hardware running

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 of the 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.