ping.cpp

00001 #include "ping.h"
00002 
00003 Ping::Ping (PinName signalPin) : mSignalIo(signalPin), mEvent(signalPin), 
00004         mBusy(0), mValid(0), mContinuous(0),
00005         mDelayBetweenReadings(DEFAULT_MEASUREMENT_DELAY_US), mTimer(), mRawReading(0) {
00006     mEvent.rise(this, &Ping::start);
00007     mEvent.fall(this, &Ping::stop);
00008 }
00009 
00010 bool Ping::startReading() {
00011     return this->startReading(false);
00012 }
00013 
00014 bool Ping::startReading(bool continuous) {
00015     mContinuous = continuous;
00016     if (mBusy) return false;
00017     
00018     mSignalIo.output();
00019     mSignalIo.write(0);
00020     wait_us(3);
00021     mSignalIo.write(1);
00022     wait_us(3);
00023     mSignalIo.write(0);
00024     mSignalIo.input();
00025     
00026     return true;
00027 }
00028 
00029 void Ping::start() {
00030     mBusy = true;
00031     mValid = false;
00032     mTimer.reset();
00033     mTimer.start();
00034 }
00035 
00036 void Ping::stop() {
00037     mBusy = false;
00038     mValid = true;
00039     // The time it takes is for a round trip.  We divide by two to get the time for one way.
00040     mRawReading = mTimer.read_us() >> 1;
00041     mTimer.stop();
00042     mCallback.call(mRawReading);
00043     if (mContinuous) mMeasureDelayTicker.attach_us(this, &Ping::nextMeasurement, mDelayBetweenReadings);
00044 }
00045 
00046 void Ping::nextMeasurement() {
00047     mMeasureDelayTicker.detach();
00048     this->startReading(mContinuous);
00049 }