The Grove - Ultrasonic ranger is a non-contact distance measurement module which works at 40KHz.
When provided a pulse trigger signal with more than 10uS through signal pin, the Grove_Ultrasonic_Ranger issues 8 cycles of 40kHz cycle level and detect the echo. The pulse width of the echo signal is proportional to the measured distance.
The Formula: Distance = echo signal high time * Sound speed (340M/S)/2.
Grove_Ultrasonic_Ranger's trig and echo signal shares 1 SIG pin.
Raspberry Pi Library (Coming Soon)