TVZ Mechatronics Team / Mbed 2 deprecated HC-SR04

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

Dependencies:   mbed HCSR04 AutomationElements

The purpose of this program is to encourage students to develope their own classes. Instructions how to follow the development of this program and class HCSR04 for ultrasonic distance measurement are given here.

main.cpp@0:ebee649c5b1b, 2015-12-03 (annotated)

Committer:
tbjazic
Date:
Thu Dec 03 15:43:54 2015 +0000
Revision:
0:ebee649c5b1b
Child:
1:22043b67c31c
Revision 1: Solution in the main program, without class.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
tbjazic 0:ebee649c5b1b 1 /** Initial test of the ultrasonic sensor HC-SR04 */
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 InterruptIn echo(p5); // echo pin
tbjazic 0:ebee649c5b1b 7 DigitalOut trigger(p7); // trigger pin
tbjazic 0:ebee649c5b1b 8 Timer timer; // echo pulsewidth measurement
tbjazic 0:ebee649c5b1b 9
tbjazic 0:ebee649c5b1b 10 /** Start the echo pulsewidth measurement */
tbjazic 0:ebee649c5b1b 11 void startTimer() {
tbjazic 0:ebee649c5b1b 12 timer.start(); // start the timer
tbjazic 0:ebee649c5b1b 13 }
tbjazic 0:ebee649c5b1b 14
tbjazic 0:ebee649c5b1b 15 /** Stop the echo pulsewidth measurement */
tbjazic 0:ebee649c5b1b 16 void stopTimer() {
tbjazic 0:ebee649c5b1b 17 timer.stop(); // stop the timer
tbjazic 0:ebee649c5b1b 18 }
tbjazic 0:ebee649c5b1b 19
tbjazic 0:ebee649c5b1b 20 int main() {
tbjazic 0:ebee649c5b1b 21 /** configure the rising edge to start the timer */
tbjazic 0:ebee649c5b1b 22 echo.rise(&startTimer);
tbjazic 0:ebee649c5b1b 23
tbjazic 0:ebee649c5b1b 24 /** configure the falling edge to stop the timer */
tbjazic 0:ebee649c5b1b 25 echo.fall(&stopTimer);
tbjazic 0:ebee649c5b1b 26
tbjazic 0:ebee649c5b1b 27 while(1) {
tbjazic 0:ebee649c5b1b 28 /** Start the measurement by sending the 10us trigger pulse */
tbjazic 0:ebee649c5b1b 29 trigger = 1;
tbjazic 0:ebee649c5b1b 30 wait_us(10);
tbjazic 0:ebee649c5b1b 31 trigger = 0;
tbjazic 0:ebee649c5b1b 32
tbjazic 0:ebee649c5b1b 33 /** Wait for the sensor to finish measurement (generate rise and fall interrupts).
tbjazic 0:ebee649c5b1b 34 * Minimum wait time is determined by maximum measurement distance of 400 cm.
tbjazic 0:ebee649c5b1b 35 * t_min = 400 * 58 = 23200 us = 23.2 ms */
tbjazic 0:ebee649c5b1b 36 wait(1);
tbjazic 0:ebee649c5b1b 37
tbjazic 0:ebee649c5b1b 38 /** calculate the distance in cm */
tbjazic 0:ebee649c5b1b 39 float distance = timer.read() * 1e6 / 58;
tbjazic 0:ebee649c5b1b 40 timer.reset(); // reset the timer to 0
tbjazic 0:ebee649c5b1b 41
tbjazic 0:ebee649c5b1b 42 /** Print the result in cm to the terminal with 1 decimal place
tbjazic 0:ebee649c5b1b 43 * (number 5 after % means that total of 5 digits will be reserved
tbjazic 0:ebee649c5b1b 44 * for printing the number, including the dot and one decimal place). */
tbjazic 0:ebee649c5b1b 45 pc.printf("Distance: %5.1f cm\r", distance);
tbjazic 0:ebee649c5b1b 46 }
tbjazic 0:ebee649c5b1b 47 }