Freenove ESP32 - Page 112

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110
Chapter 10 Ultrasonic Ranging
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UltrasonicRanging.cpp
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#include "UltrasonicRanging.h"
constexpr int MAX_DISTANCE = 300; // Maximum sensor distance is rated at 400-500cm.
constexpr float timeOut = MAX_DISTANCE * 60; // timeOut= 2*MAX_DISTANCE /100 /340 *1000000 =
MAX_DISTANCE*58.8
constexpr int soundVelocity = 340; // define sound speed=340m/s
void setupSonar() {
pinMode(PIN_TRIG, OUTPUT); // set trigPin to output mode
pinMode(PIN_ECHO, INPUT); // set echoPin to input mode
}
float getSonar() {
unsigned long pingTime, t0, t1;
float distance;
// make PIN_TRIG output high level lasting for 10μs to triger HC_SR04
digitalWrite(PIN_TRIG, HIGH);
delayMicroseconds(10);
digitalWrite(PIN_TRIG, LOW);
// Wait HC-SR04 returning to the high level and measure out this waitting time
t0 = micros();
pingTime = pulseIn(PIN_ECHO, HIGH, timeOut); // unit: us
t1 = micros() - t0;
// calculate the distance according to the time
if (t1 < timeOut) {
distance = (float)pingTime * soundVelocity / 2 / 10000;
} else {
distance = MAX_DISTANCE;
}
return distance; // return the distance value
}
Ultrasonic module initialization function.
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void setupSonar() {
pinMode(PIN_TRIG, OUTPUT); // set trigPin to output mode
pinMode(PIN_ECHO, INPUT); // set echoPin to input mode
}