How to use hall effect sensor??

Hi ,  Greetings to all, I am trying to use a hall effect sensor for which I need the digital port 2 to use the function; "AttachInterrupt (0, flow, RISING);", I tried to modify the firfly signature, but without success, if someone could lend me a hand.

I leave the sketch that I need to run in firefly in attachments in txt.

I also leave the signature code of firefly modified ... (I rely on one that is in the next thread, of course they use another sensor. "Ping ping")

Thank you very much for your help