I recently recieved some HC-SR04's and am wanting to make a little device to test them. The idea is that one sensor controls when a piezo buzzer will play, and the other sensor will decide the pitch of that note. I have written some code together but on trying to compile I get this error:
core.a(Tone.cpp.o): In function `__vector_7':
C:\Program Files (x86)\arduino-1.0.1\hardware\arduino\cores\arduino/Tone.cpp:523: multiple definition of `__vector_7'