HCSR04.h

00001 #ifndef HCSR04_H
00002 #define HCSR04_H
00003 
00004 // The following lines MUST be added into the main() routine
00005 /*
00006 HCSR04_timer.start();
00007 HCSR04_echo.rise(&echo_start);
00008 HCSR04_echo.fall(&echo_end);
00009 HCSR04_start.attach(&pulse_trigger, 100E-3);
00010 */
00011 
00012 DigitalOut HCSR04_trigger(PTC13);
00013 InterruptIn HCSR04_echo(PTC16); 
00014 Ticker HCSR04_start;
00015 Timer HCSR04_timer;
00016 float HCSR04_time, HCSR04_inches, HCSR04_cm;
00017 
00018 void HCSR04_pulse_trigger()
00019 {
00020     HCSR04_trigger.write(1);
00021     wait(10E-6);
00022     HCSR04_trigger.write(0);
00023 }
00024 
00025 void HCSR04_echo_start()
00026 {
00027     HCSR04_timer.reset();
00028 }
00029 
00030 void HCSR04_echo_end()
00031 {
00032     HCSR04_time=HCSR04_timer.read();
00033     if(HCSR04_time < 30E-3)   // delay longer than 30 ms indicates no echo
00034     {
00035         HCSR04_inches=HCSR04_time*13503.9*0.5;     // speed of sound = 13503.9 inches/second and distance to object is 1/2 path length;
00036         HCSR04_cm=HCSR04_time*34300.0*0.5;     // speed of sound = 34300 cm/second and distance to object is 1/2 path length;
00037     }
00038     else
00039     {
00040         HCSR04_inches=-1.0;
00041         HCSR04_cm=-1.0;
00042     }
00043 }
00044 
00045 
00046 #endif //HCSR04_H