BULME_BHEL18 / distance

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Show/hide line numbers distance.cpp Source File

distance.cpp

00001 // HC-SR04 Device
00002 #include "distance.h"
00003 #include "mbed.h"
00004 
00005 Timer pulsetime;
00006 DigitalOut  trigger(p21);
00007 InterruptIn echo(p22);
00008 unsigned int pulsedur;
00009 unsigned int distance;
00010 
00011 void isr_rise(void)
00012 {
00013     pulsetime.start();
00014 }
00015 
00016 void isr_fall(void)
00017 {
00018     pulsetime.stop();
00019     pulsedur = pulsetime.read_us();
00020     distance= (pulsedur*343)/20000;
00021     pulsetime.reset();
00022 }
00023 
00024 unsigned int getDist() //cm
00025 {
00026     // init   
00027     pulsetime.stop();
00028     pulsetime.reset();
00029     echo.rise(&isr_rise);
00030     echo.fall(&isr_fall);
00031     trigger=0;
00032     
00033     // start
00034     trigger=1;
00035     wait_us(10);
00036     trigger=0; 
00037     wait_us(10);
00038     
00039     return distance;
00040 }
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