jakob hz / Mbed 2 deprecated HC-SR04-2410

A program that demonstrates the development of library, using as an example an ultrasonic distance sensor HC-SR04.

Dependencies:   mbed HCSR04 AutomationElements

main.cpp@1:22043b67c31c, 2015-12-04 (annotated)

Committer:
tbjazic
Date:
Fri Dec 04 17:38:02 2015 +0000
Revision:
1:22043b67c31c
Parent:
0:ebee649c5b1b
Child:
2:f86b1e3609b3
A class HCSR04 implemented within the main.cpp file.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
tbjazic 1:22043b67c31c 1 /** Revision 1: Building the class */
tbjazic 0:ebee649c5b1b 2
tbjazic 0:ebee649c5b1b 3 #include "mbed.h"
tbjazic 0:ebee649c5b1b 4
tbjazic 0:ebee649c5b1b 5 Serial pc(USBTX, USBRX); // communication with terminal
tbjazic 0:ebee649c5b1b 6
tbjazic 1:22043b67c31c 7 class HCSR04 {
tbjazic 1:22043b67c31c 8
tbjazic 1:22043b67c31c 9 public:
tbjazic 1:22043b67c31c 10
tbjazic 1:22043b67c31c 11 /** Receives two PinName variables.
tbjazic 1:22043b67c31c 12 * @param echoPin mbed pin to which the echo signal is connected to
tbjazic 1:22043b67c31c 13 * @param triggerPin mbed pin to which the trigger signal is connected to
tbjazic 1:22043b67c31c 14 */
tbjazic 1:22043b67c31c 15 HCSR04(PinName echoPin, PinName triggerPin);
tbjazic 1:22043b67c31c 16
tbjazic 1:22043b67c31c 17 /** Calculates the distance in cm, with the calculation time of 25 ms.
tbjazic 1:22043b67c31c 18 * @returns distance of the measuring object in cm.
tbjazic 1:22043b67c31c 19 */
tbjazic 1:22043b67c31c 20 float getDistance_cm();
tbjazic 1:22043b67c31c 21
tbjazic 1:22043b67c31c 22 private:
tbjazic 1:22043b67c31c 23
tbjazic 1:22043b67c31c 24 InterruptIn echo; // echo pin
tbjazic 1:22043b67c31c 25 DigitalOut trigger; // trigger pin
tbjazic 1:22043b67c31c 26 Timer timer; // echo pulsewidth measurement
tbjazic 1:22043b67c31c 27 float distance; // store the distance in cm
tbjazic 1:22043b67c31c 28
tbjazic 1:22043b67c31c 29 /** Start the timer. */
tbjazic 1:22043b67c31c 30 void startTimer();
tbjazic 1:22043b67c31c 31
tbjazic 1:22043b67c31c 32 /** Stop the timer. */
tbjazic 1:22043b67c31c 33 void stopTimer();
tbjazic 1:22043b67c31c 34
tbjazic 1:22043b67c31c 35 /** Initialization. */
tbjazic 1:22043b67c31c 36 void init();
tbjazic 1:22043b67c31c 37
tbjazic 1:22043b67c31c 38 /** Start the measurement. */
tbjazic 1:22043b67c31c 39 void startMeasurement();
tbjazic 1:22043b67c31c 40 };
tbjazic 1:22043b67c31c 41
tbjazic 1:22043b67c31c 42
tbjazic 1:22043b67c31c 43 HCSR04::HCSR04(PinName echoPin, PinName triggerPin) : echo(echoPin), trigger(triggerPin) {
tbjazic 1:22043b67c31c 44 init();
tbjazic 1:22043b67c31c 45 }
tbjazic 1:22043b67c31c 46
tbjazic 1:22043b67c31c 47 void HCSR04::init() {
tbjazic 1:22043b67c31c 48 /** configure the rising edge to start the timer */
tbjazic 1:22043b67c31c 49 echo.rise(this, &HCSR04::startTimer);
tbjazic 1:22043b67c31c 50
tbjazic 1:22043b67c31c 51 /** configure the falling edge to stop the timer */
tbjazic 1:22043b67c31c 52 echo.fall(this, &HCSR04::stopTimer);
tbjazic 1:22043b67c31c 53
tbjazic 1:22043b67c31c 54 distance = -1; // initial distance
tbjazic 1:22043b67c31c 55 }
tbjazic 1:22043b67c31c 56
tbjazic 1:22043b67c31c 57 void HCSR04::startTimer() {
tbjazic 0:ebee649c5b1b 58 timer.start(); // start the timer
tbjazic 0:ebee649c5b1b 59 }
tbjazic 0:ebee649c5b1b 60
tbjazic 1:22043b67c31c 61 void HCSR04::stopTimer() {
tbjazic 0:ebee649c5b1b 62 timer.stop(); // stop the timer
tbjazic 0:ebee649c5b1b 63 }
tbjazic 0:ebee649c5b1b 64
tbjazic 1:22043b67c31c 65 void HCSR04::startMeasurement() {
tbjazic 1:22043b67c31c 66 /** Start the measurement by sending the 10us trigger pulse. */
tbjazic 1:22043b67c31c 67 trigger = 1;
tbjazic 1:22043b67c31c 68 wait_us(10);
tbjazic 1:22043b67c31c 69 trigger = 0;
tbjazic 1:22043b67c31c 70
tbjazic 1:22043b67c31c 71 /** Wait for the sensor to finish measurement (generate rise and fall interrupts).
tbjazic 1:22043b67c31c 72 * Minimum wait time is determined by maximum measurement distance of 400 cm.
tbjazic 1:22043b67c31c 73 * t_min = 400 * 58 = 23200 us = 23.2 ms */
tbjazic 1:22043b67c31c 74 wait_ms(25);
tbjazic 1:22043b67c31c 75
tbjazic 1:22043b67c31c 76 /** calculate the distance in cm */
tbjazic 1:22043b67c31c 77 distance = timer.read() * 1e6 / 58;
tbjazic 1:22043b67c31c 78 timer.reset(); // reset the timer to 0 after storing the distance
tbjazic 1:22043b67c31c 79 }
tbjazic 1:22043b67c31c 80
tbjazic 1:22043b67c31c 81 float HCSR04::getDistance_cm() {
tbjazic 1:22043b67c31c 82 startMeasurement();
tbjazic 1:22043b67c31c 83 return distance;
tbjazic 1:22043b67c31c 84 }
tbjazic 1:22043b67c31c 85
tbjazic 0:ebee649c5b1b 86 int main() {
tbjazic 1:22043b67c31c 87 HCSR04 sensor(p5, p7); // instantiate the sensor object
tbjazic 0:ebee649c5b1b 88 while(1) {
tbjazic 1:22043b67c31c 89 /** Print the result in cm to the terminal with 1 decimal place
tbjazic 0:ebee649c5b1b 90 * (number 5 after % means that total of 5 digits will be reserved
tbjazic 0:ebee649c5b1b 91 * for printing the number, including the dot and one decimal place). */
tbjazic 1:22043b67c31c 92 pc.printf("Distance: %5.1f cm\r", sensor.getDistance_cm());
tbjazic 1:22043b67c31c 93 wait_ms(1000-25);
tbjazic 0:ebee649c5b1b 94 }
tbjazic 0:ebee649c5b1b 95 }