Some time ago I came across the Wolphilink Interface. It's a small box which connects an smartphone to a Yaesu FT-817/857/897 transceiver. I was about to buy one, but the interface was quite expensive, especially if you include the optional cables and the shipping to my QTH in Germany. I googled a bit and found an interface built by Christian Petersen, DD7LP. I made the decision to take a closer look on his schematic diagram and built my own interface to use APRSdroid and PSKdroid on my FT-817. Luckily Christian also provided a buying list besides the schematic diagram. As I don't have any knowledge and also no tools to etch a circuit board, I first planned to build the circuit on a simple stripboard.