Prabhu Desai / HCSR04

Ultrasound Ranging Sensor module

Dependents:   Obstacle_avoidance servourfmatlab hcsr04 DistanceOnSevenSegLed ... more

Overview

The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object like bats or dolphins do. It offers excellent range accuracy and stable readings in an easy-to-use package. It operation is not affected by sunlight or black material like Sharp rangefinders are (although acoustically soft materials like cloth can be difficult to detect).

Sensor (HCSR04) Details

You can find the details of the sensor at http://www.micropik.com/PDF/HCSR04.pdf /media/uploads/prabhuvd/_scaled_hcsr04.png

Working principle

The trigger input is sent a 10 usec pulse and followed by that the pulse width on the echo line is measured , the measured pulse width is then converted into distance in cm.

/media/uploads/prabhuvd/waveform.png

Quote:

Calculation : The sonic speed is 343 m/sec , when converted to cm/usec , it will 343 * 100/ 1000000 = 343 /10000 cm/usec The width of the pulse is equivalent to time taken by ultrasonic wave to reach obstacle and bounce back , hence the distance of the object will be half the pulse width.

Distance (cm) = measured pulse width * 343/20000 cm.

Schematic

/media/uploads/prabhuvd/schema.png

Code

include the mbed library with this snippet

#include "mbed.h"
#include "hcsr04.h"
#include "TextLCD.h"

DigitalOut myled(LED1);
HCSR04  usensor(p25,p6);
TextLCD lcd(p14, p16, p17, p18, p19, p20,TextLCD::LCD16x2); // rs, e, d4-d7
unsigned int dist;
int main()
{
 
    while(1) {
        usensor.start();
        wait_ms(500); 
        dist=usensor.get_dist_cm();
        lcd.cls();
        lcd.locate(0,0);
        lcd.printf("cm:%ld",dist );
 
    }
}

hcsr04.cpp@7:71da0dbf4400, 2013-03-30 (annotated)

Committer:
prabhuvd
Date:
Sat Mar 30 18:55:03 2013 +0000
Revision:
7:71da0dbf4400
Parent:
6:4be4fcd0c171 
name modified

Who changed what in which revision?

UserRevisionLine numberNew contents of line
prabhuvd 0:fb0929f37ebe 1 /* Copyright (c) 2013 Prabhu Desai
prabhuvd 0:fb0929f37ebe 2 * pdtechworld@gmail.com
prabhuvd 0:fb0929f37ebe 3 *
prabhuvd 0:fb0929f37ebe 4 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
prabhuvd 0:fb0929f37ebe 5 * and associated documentation files (the "Software"), to deal in the Software without restriction,
prabhuvd 0:fb0929f37ebe 6 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
prabhuvd 0:fb0929f37ebe 7 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
prabhuvd 0:fb0929f37ebe 8 * furnished to do so, subject to the following conditions:
prabhuvd 0:fb0929f37ebe 9 *
prabhuvd 0:fb0929f37ebe 10 * The above copyright notice and this permission notice shall be included in all copies or
prabhuvd 0:fb0929f37ebe 11 * substantial portions of the Software.
prabhuvd 0:fb0929f37ebe 12 *
prabhuvd 0:fb0929f37ebe 13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
prabhuvd 0:fb0929f37ebe 14 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
prabhuvd 0:fb0929f37ebe 15 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
prabhuvd 0:fb0929f37ebe 16 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
prabhuvd 0:fb0929f37ebe 17 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
prabhuvd 0:fb0929f37ebe 18 */
prabhuvd 0:fb0929f37ebe 19
prabhuvd 0:fb0929f37ebe 20
prabhuvd 0:fb0929f37ebe 21 #include "hcsr04.h"
prabhuvd 0:fb0929f37ebe 22
prabhuvd 0:fb0929f37ebe 23
prabhuvd 6:4be4fcd0c171 24 HCSR04::HCSR04(PinName TrigPin,PinName EchoPin):
prabhuvd 2:0acb6ade091c 25 trigger(TrigPin), echo(EchoPin)
prabhuvd 0:fb0929f37ebe 26 {
prabhuvd 0:fb0929f37ebe 27 pulsetime.stop();
prabhuvd 0:fb0929f37ebe 28 pulsetime.reset();
prabhuvd 6:4be4fcd0c171 29 echo.rise(this,&HCSR04::isr_rise);
prabhuvd 6:4be4fcd0c171 30 echo.fall(this,&HCSR04::isr_fall);
prabhuvd 2:0acb6ade091c 31 trigger=0;
prabhuvd 0:fb0929f37ebe 32 }
prabhuvd 0:fb0929f37ebe 33
prabhuvd 6:4be4fcd0c171 34 HCSR04::~HCSR04()
prabhuvd 0:fb0929f37ebe 35 {
prabhuvd 0:fb0929f37ebe 36 }
prabhuvd 0:fb0929f37ebe 37
prabhuvd 6:4be4fcd0c171 38 void HCSR04::isr_rise(void)
prabhuvd 0:fb0929f37ebe 39 {
prabhuvd 0:fb0929f37ebe 40 pulsetime.start();
prabhuvd 0:fb0929f37ebe 41 }
prabhuvd 6:4be4fcd0c171 42 void HCSR04::start(void)
prabhuvd 2:0acb6ade091c 43 {
prabhuvd 2:0acb6ade091c 44 trigger=1;
prabhuvd 2:0acb6ade091c 45 wait_us(10);
prabhuvd 2:0acb6ade091c 46 trigger=0;
prabhuvd 2:0acb6ade091c 47 }
prabhuvd 0:fb0929f37ebe 48
prabhuvd 6:4be4fcd0c171 49 void HCSR04::isr_fall(void)
prabhuvd 0:fb0929f37ebe 50 {
prabhuvd 0:fb0929f37ebe 51 pulsetime.stop();
prabhuvd 0:fb0929f37ebe 52 pulsedur = pulsetime.read_us();
prabhuvd 0:fb0929f37ebe 53 distance= (pulsedur*343)/20000;
prabhuvd 0:fb0929f37ebe 54 pulsetime.reset();
prabhuvd 0:fb0929f37ebe 55 }
prabhuvd 4:33938a97d904 56
prabhuvd 6:4be4fcd0c171 57 void HCSR04::rise (void (*fptr)(void))
prabhuvd 0:fb0929f37ebe 58 {
prabhuvd 0:fb0929f37ebe 59 echo.rise(fptr);
prabhuvd 0:fb0929f37ebe 60 }
prabhuvd 6:4be4fcd0c171 61 void HCSR04::fall (void (*fptr)(void))
prabhuvd 0:fb0929f37ebe 62 {
prabhuvd 0:fb0929f37ebe 63 echo.fall(fptr);
prabhuvd 0:fb0929f37ebe 64 }
prabhuvd 0:fb0929f37ebe 65
prabhuvd 6:4be4fcd0c171 66 unsigned int HCSR04::get_dist_cm()
prabhuvd 0:fb0929f37ebe 67 {
prabhuvd 2:0acb6ade091c 68 return distance;
prabhuvd 0:fb0929f37ebe 69 }
prabhuvd 6:4be4fcd0c171 70 unsigned int HCSR04::get_pulse_us()
prabhuvd 2:0acb6ade091c 71 {
prabhuvd 2:0acb6ade091c 72 return pulsedur;
prabhuvd 2:0acb6ade091c 73 }
prabhuvd 5:e70a24a88131 74
prabhuvd 5:e70a24a88131 75
prabhuvd 5:e70a24a88131 76
prabhuvd 5:e70a24a88131 77 /*******************************************************
prabhuvd 5:e70a24a88131 78 Here is a sample code usage
prabhuvd 5:e70a24a88131 79 *********************************************************
prabhuvd 5:e70a24a88131 80 #include "hcsr04.h"
prabhuvd 6:4be4fcd0c171 81 HCSR04 usensor(p25,p6);
prabhuvd 5:e70a24a88131 82 int main()
prabhuvd 5:e70a24a88131 83 {
prabhuvd 5:e70a24a88131 84 unsigned char count=0;
prabhuvd 5:e70a24a88131 85 while(1) {
prabhuvd 5:e70a24a88131 86 usensor.start();
prabhuvd 5:e70a24a88131 87 wait_ms(500);
prabhuvd 5:e70a24a88131 88 dist=usensor.get_dist_cm();
prabhuvd 5:e70a24a88131 89 lcd.cls();
prabhuvd 5:e70a24a88131 90 lcd.locate(0,0);
prabhuvd 5:e70a24a88131 91 lcd.printf("cm:%ld",dist );
prabhuvd 5:e70a24a88131 92
prabhuvd 5:e70a24a88131 93 count++;
prabhuvd 5:e70a24a88131 94 lcd.locate(0,1);
prabhuvd 5:e70a24a88131 95 lcd.printf("Distance =%d",count);
prabhuvd 5:e70a24a88131 96
prabhuvd 5:e70a24a88131 97 }
prabhuvd 5:e70a24a88131 98 */