I have the same set-up of Maxbotix sonar with Mayfly as Steven. I did some trials first with my arduino and analog signal reading which was succesfull.
Now I trying the serial code available on the enviroDIY website, but readings are 0 mm. I hope following questions may help me to get succesfull measurements:
1) In the code the pin 5 is D5 of the mayfly?
2) The GND and 3.3V of the D pins is used?
3) To the pin 5 of the mayfly I connect the signal of output 2 (PulseWidth) of the maxbotix?
Any other checks I can make to resolve this issue? Thanks in advance.
Have a nice weekend.