Diff: HCSR04.cpp

Revision:

4:d76458b00616

Parent:

3:9ddabd24f48c

diff -r 9ddabd24f48c -r d76458b00616 HCSR04.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HCSR04.cpp	Sun Dec 03 18:47:45 2017 +0000
@@ -0,0 +1,60 @@
+#include "mbed.h"
+#include "HCSR04.h"
+/*
+    HCSR04.h
+    Written by Leong Kum Loong.
+    04 Dec 2017, REV. 0
+    
+    All routines and functions in this library are written by me solely.
+    Library for HC-SR04 Ultrasonic Ranging sensor.
+    Library uses pins p21 to send pulse to sensor Trigger input & p22 to read sensor Echo output.
+    This is assuming velocity of sound rate from ultrasonic pulse is 340m/s.
+*/
+
+DigitalOut trig(p21);
+DigitalIn echo(p22);
+Timer echoTime;
+Ticker interval;
+
+float distance = 0;
+
+float divisor;
+
+static void findDistance(){
+    trig = 1;
+    wait_ms(10);
+    trig = 0;
+    wait_ms(20);
+    
+    trig = 1;
+    wait_us(10);
+    trig = 0;
+    
+    while(!echo);
+    echoTime.start();
+    while(echo);
+    echoTime.stop();
+    
+    distance = (float)echoTime.read_us()/(float)2 * 0.034 / (float)divisor;
+    echoTime.reset();
+}
+
+//Start monitoring distance.
+void getDistance(int unit){
+    //1 for CM & 2 for INCH
+    switch(unit){
+    case 1:
+        divisor = 1;        //Default divisor to get CM.
+        break;
+    case 2:
+        divisor = 2.54;     //Divisor to get INCH.
+        break;    
+    }
+
+    interval.attach(findDistance, 0.1);
+}
+
+//Retrieve distance stored.
+float readDistance(){
+    return distance;    
+}
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