File content as of revision 1:72fbcb01291d:

#include "ping.h"

Ping::Ping(PinName signalPin) : mSignalIo(signalPin, PIN_OUTPUT, PullDown, 0), mEvent(signalPin), 
        mBusy(0), mValid(0), mContinuous(0), mTimer(), mRawReading(0) {
    mEvent.rise(this, &Ping::start);
    mEvent.fall(this, &Ping::stop);
}

bool Ping::startReading() {
    return this->startReading(false);
}

bool Ping::startReading(bool continuous) {
    mContinuous = continuous;
    if (mBusy) return false;
    
    mSignalIo.output();
    mSignalIo = 0;
    wait_us(2);
    mSignalIo = 1;
    wait_us(10);
    mSignalIo.input();
    
    return true;
}

void Ping::start() {
    mBusy = true;
    mValid = false;
    mTimer.start();
    mStartTime = mTimer.read_us();
}

void Ping::stop() {
    mBusy = false;
    mValid = true;
    // The time it takes is for a round trip.  We divide by two to get the time for one way.
    mRawReading = (mTimer.read_us() - mStartTime) >> 1;
    mTimer.stop();
    mCallback.call(mRawReading);
    if (mContinuous) mMeasureDelayTicker.attach_us(this, &Ping::nextMeasurement, 5000);
}

void Ping::nextMeasurement() {
    mMeasureDelayTicker.detach();
    this->startReading(mContinuous);
}