HC-SR04 ultrasonic module can offer non-contact distance sensing function;
Includes ultrasonic transmitter, receiver and control circuit;
Operation requirement: Take IO port TRIG to trigger ranging.It needs 10 us high level signal at least.
Operating principle :
1.It can send 8 pro 40 kz square wave automatically, and will test if there is any signal returned.
2.If there is signal returned, output one high level signal via IO port ECHO.
3.The duration of the high level signal is the time from transmitter to receiving with the ultrasonic.