"thanks for the info. when i run the code i only get weird letters instead of values. weird, will look unto it some more. I only have a motor connected to a battery without a real quad, just want to know the rpm of the motor. Could the ground be the…"

"Hi Randy,

Thanks for the program and how to guide. I just wonder, i see a wire from your digital pin 0 going somewhere, and its also in the code as interrupt pin. Where is this wire going, as i don't see it connected to any other  wire of the rpm…"