Daniel Casner / MaxbotixDriver

A driver library for Maxbotix / Maxsonar sonar range finders that uses the pulse width output function to achieve better accuracy with less load on the mbed processor.

Dependents:   QuadCopter mbed-IBooth-ETH

sonar.cpp

Committer:
DanielC
Date:
2012-11-21
Revision:
0:7e65f5077f5a

File content as of revision 0:7e65f5077f5a:

#include "sonar.h"

Sonar::Sonar(PinName input, Timer& t) :
    interrupt(input),
    time(t),
    pulseStartTime(0),
    range(0) {
    interrupt.rise(this, &Sonar::pulseStart);
    interrupt.fall(this, &Sonar::pulseStop);
}

int Sonar::read() {
    return range;
}

Sonar::operator int() {
    return read();
}

void Sonar::pulseStart() {
    pulseStartTime = time.read_us();
}

void Sonar::pulseStop() {
    int endTime = time.read_us();
    if (endTime < pulseStartTime) return; // Escape if there's been a roll over
    range = (endTime - pulseStartTime) / 58; // 58uS per CM
}