How to Use a Bluetooth GPS(转载自nokia论坛)

How to Use a Bluetooth GPS

The GPS class shows how to use a Bluetooth GPS device and read location information from it. It displays a selection dialog for the user and starts receiving data from the selected device. Currently it only parses the RMC message which is required in all GPS devices. This gives the latitude, longitude, heading and speed information but not altitude nor dilution.

You need to implement messaging for lost signal etc if you want to show them to the user.

You can also use the Parse() method to convert the received values to degrees, minutes and seconds as well as a combined integer value multiplied by 65536.

This example assumes that the GPS device uses RFCOMM channel 1 as data channel. This has been the case in every device I've used, so it's a safe assumption.

GPS.h

#ifndef GPS_H_

#define GPS_H_

#include <e32std.h>

#include <btmanclient.h>

#include <btextnotifiers.h>

#include <es_sock.h>

#include <in_sock.h>

#include <bt_sock.h>

class GPS : public CActive

{

public:

GPS();

virtual ~GPS();

void ConstructL();

void DoCancel();

void RunL();

TPtrC Lat();

TPtrC Lon();

TInt speed, heading;

private:

TBool Active;

TBuf8<32> lat, lon;

TBuf8<256> line;

TBuf8<32> data;

int state;

RSocket iSendingSocket;

RSocketServ iSocketServer;

};

#endif /*GPS_H_*/

GPS.cpp

#include "GPS.h"

#include <e32math.h>

_LIT8(ZERO, "0");

_LIT(RFCOMM, "RFCOMM");

_LIT8(KGPS, "GPS");

void Parse(TDesC8 &data, TInt °, TInt &min, TInt &sec, TInt32 &whole)

{

TLex8 lex(data);

lex.Val(deg);

lex.Inc();

lex.Val(min);

sec = min * 60;

int l = (data.Length() - data.Find(_L8(".")));

int x = 1;

while (l-- > 0)

x *= 10;

sec /= x/100;

min = deg % 100;

deg /= 100;

whole = deg * 65536 + (min * 65536 / 60) + (sec * 65536 / 36000);

}

GPS::GPS() : CActive(EPriorityLow)

{

state = 0;

}

GPS::~GPS()

{

TRAPD(err, Cancel());

TRAP(err, Deque());

}

void GPS::RunL()

{

int i, j;

if (iStatus == KErrNone)

{

if (state == 1)

{

state = 2;

line.Zero();

iSendingSocket.Read(data, iStatus);

SetActive();

}

else if (state == 2)

{

int rpos = 0;

while ((rpos = data.Locate('\r')) != KErrNotFound)

{

line.Append(data.Left(rpos));

if (data.Length() > rpos + 2)

{

if (data[rpos + 1] == '\n')

data.Copy(data.Mid(rpos+2));

else

data.Copy(data.Mid(rpos+1));

}

else

{

data.Zero();

}

if (line.Length() > 10)

{

// RMC - lat, lon, speed

if ((line[3] == 'R') && (line[4] == 'M') && (line[5] == 'C'))

{

j = i = 0;

while ((i < line.Length()) && (line[i] != ','))

i++;

i++;

j = i;

while ((i < line.Length()) && (line[i] != ','))

i++;

i++;

// If there is no signal, this is not A

if (line[i] != 'A')

{

lat.Copy(ZERO);

lon.Copy(ZERO);

latdeg = londeg = latmin = lonmin = latsec = lonsec = 0;

line.Zero();

iSendingSocket.Read(data, iStatus);

SetActive();

return;

}

while ((i < line.Length()) && (line[i] != ','))

i++;

i++;

j = i;

while ((i < line.Length()) && (line[i] != ','))

i++;

// Copy latitude from the message

lat.Copy(line.Mid(j, i-j));

// If it's southern hemisphere, negate the value

if (line[i+1] == 'S')

lat.Insert(0, _L8("-"));

i += 3;

j = i;

while ((i < line.Length()) && (line[i] != ','))

i++;

// Copy longitude from the message

lon.Copy(line.Mid(j, i-j));

// If it's western hemisphere, negate the value

if (line[i+1] == 'W')

lon.Insert(0, _L8("-"));

i += 3;

j = i;

while ((i < line.Length()) && (line[i] != ','))

i++;

// Read speed from the message

TLex8 lex(line.Mid(j, i-j));

lex.Val(speed);

speed *= 10;

if (lex.Peek() == '.')

{

lex.Inc();

if (lex.Peek() != 0)

speed += ((int)lex.Peek() - '0');

}

// Convert speed from knots to km/h

speed *= 1852;

speed /= 1000;

i++;

j = i;

while ((i < line.Length()) && (line[i] != ','))

i++;

// Read heading from the message

lex.Assign(line.Mid(j, i-j));

lex.Val(heading);

heading *= 10;

// Check if it's not integer

if (lex.Peek() == '.')

{

lex.Inc();

if (lex.Peek() != 0)

heading += ((int)lex.Peek() - '0');

}

}

}

line.Zero();

}

line.Append(data);

iSendingSocket.Read(data, iStatus);

SetActive();

}

}

// Error occurred...

else

{

lat.Copy(ZERO);

lon.Copy(ZERO);

}

}

void GPS::DoCancel()

{

if (state > 0)

iSendingSocket.Close();

iSocketServer.Close();

}

void GPS::ConstructL()

{

TBTDeviceResponseParamsPckg resultPckg;

CActiveScheduler::Add(this);

// 1. Create a notifier

RNotifier notif;

User::LeaveIfError(notif.Connect());

if (gpsid.Length() == 0)

{

state = 0;

// 2. Start the device selection plug-in

TBTDeviceSelectionParams selectionFilter;

TUUID targetServiceClass(0x2345);

selectionFilter.SetUUID(targetServiceClass);

TBTDeviceSelectionParamsPckg pckg(selectionFilter);

TRequestStatus status;

notif.StartNotifierAndGetResponse(status,

KDeviceSelectionNotifierUid, pckg, resultPckg);

User::After(2000000);

// 3. Extract device name if it was returned

User::WaitForRequest(status);

User::LeaveIfError(iSocketServer.Connect());

if (status.Int() == KErrNone)

{

User::LeaveIfError(iSendingSocket.Open(iSocketServer,

RFCOMM));

TBTSockAddr address;

gpsid.Copy(resultPckg().BDAddr().Des());

address.SetBTAddr(resultPckg().BDAddr());

// GPS devices usually use port 1 as data channel

// so we don't have to query it

address.SetPort(1);

state = 1;

iSendingSocket.Connect(address, iStatus);

SetActive();

}

else

{

CHainMAppView::Static()->Notification(EGPSNotFound);

}

}

else

{

User::LeaveIfError(iSocketServer.Connect());

User::LeaveIfError(iSendingSocket.Open(iSocketServer, RFCOMM));

TBTSockAddr address;

TBTDevAddr a(gpsid);

address.SetBTAddr(a);

address.SetPort(1);

state = 1;

iSendingSocket.Connect(address, iStatus);

SetActive();

}

}

TPtrC GPS::Lat()

{

return lat;

}

TPtrC GPS::Lon()

{

return lon;

}