The Mark I FlexRadio Controller was an Arduino-only development. It's what got me started on writing FlexRadio controllers and was instrumental in my early understanding of how the API worked and what was needed in a controller.
The Mk I controller has now been fully superseded by the Mk II development. I no longer have the ability to test the code, as I do not have any Mk I controller hardware now. You are welcome to use this design if you wish but I can offer no detailed support, nor can I undertake any software changes.