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@0:7e65f5077f5a, 2012-11-21 (annotated)

Committer:
DanielC
Date:
Wed Nov 21 20:47:05 2012 +0000
Revision:
0:7e65f5077f5a
Initial commit of probably working but untested sonar driver library.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DanielC 0:7e65f5077f5a 1 #include "sonar.h"
DanielC 0:7e65f5077f5a 2
DanielC 0:7e65f5077f5a 3 Sonar::Sonar(PinName input, Timer& t) :
DanielC 0:7e65f5077f5a 4 interrupt(input),
DanielC 0:7e65f5077f5a 5 time(t),
DanielC 0:7e65f5077f5a 6 pulseStartTime(0),
DanielC 0:7e65f5077f5a 7 range(0) {
DanielC 0:7e65f5077f5a 8 interrupt.rise(this, &Sonar::pulseStart);
DanielC 0:7e65f5077f5a 9 interrupt.fall(this, &Sonar::pulseStop);
DanielC 0:7e65f5077f5a 10 }
DanielC 0:7e65f5077f5a 11
DanielC 0:7e65f5077f5a 12 int Sonar::read() {
DanielC 0:7e65f5077f5a 13 return range;
DanielC 0:7e65f5077f5a 14 }
DanielC 0:7e65f5077f5a 15
DanielC 0:7e65f5077f5a 16 Sonar::operator int() {
DanielC 0:7e65f5077f5a 17 return read();
DanielC 0:7e65f5077f5a 18 }
DanielC 0:7e65f5077f5a 19
DanielC 0:7e65f5077f5a 20 void Sonar::pulseStart() {
DanielC 0:7e65f5077f5a 21 pulseStartTime = time.read_us();
DanielC 0:7e65f5077f5a 22 }
DanielC 0:7e65f5077f5a 23
DanielC 0:7e65f5077f5a 24 void Sonar::pulseStop() {
DanielC 0:7e65f5077f5a 25 int endTime = time.read_us();
DanielC 0:7e65f5077f5a 26 if (endTime < pulseStartTime) return; // Escape if there's been a roll over
DanielC 0:7e65f5077f5a 27 range = (endTime - pulseStartTime) / 58; // 58uS per CM
DanielC 0:7e65f5077f5a 28 }