Modified version of "AD9833 Waveform Generator" from http://www.vwlowen.co.uk/arduino/AD9833-waveform-generator/AD9833-waveform-generator.htm
I made some adjustments to make the GUI look and feel better. Support for a DS3231 RTC was added too. Additionally a 3D-Model of a 3D-printable Case designed by me and some images are available on Thingiverse (https://www.thingiverse.com/thing:2999358).