Bluetooth Low Energy

[flemingp]

Hello ........

I am writing some logging software running on raspberry pi using QT. I have successfully interfaced with all the sensors using a wired serial port and a standard bluetooth to serial device (HC-05) . The sensors all output text data via a serial port.

I now want to use a blue tooth low energy device, the module I am using is the BT4.0 HM-10, which acts a pass through device for the serial text data.


I have been partially successful in using the heartlistener code as a reference, however, as soon as I



m_control->connectToDevice();

I start to receive the following output in the console:

qt.bluetooth.bluez: cannot find matching characteristic for notification/indication

This is before I


m_control->discoverServices();


After doing service discovery and using a slot to catch characteristic changed signal I am able to output the line of text from the custom service of the HM-10 module BUT this happens even before I enable change notifications for the characteristic. i.e. if I take the code out from this function I still get notifications:



void leConnection::serviceStateChanged(QLowEnergyServic e::ServiceState s)


I should add all this code is being run on ubuntu and not the raspberry pi, for which I use a cross complier when I have the final code.


I have tried disabling notifications but I still get change notifications processed by:



void leConnection::updateSerialValue(const QLowEnergyCharacteristic &c, const QByteArray &value)



Any help or tips much appreciated.


Paul





Full code:



#include "leconnection.h"

leConnection::leConnection()
{

// connect(m_deviceDiscoveryAgent, SIGNAL(finished()), this, SLOT(scanFinished()));

hm10Name = "MainStart"; //HMSoft

hm10Address = "A4:D5:78:69:C0:AF"; //A4:D5:78:69:C0:AF

hm10ServiceId = "0000FFE0-0000-1000-8000-00805F9B34FB";

ptrHM10serial = new QBluetoothUuid(hm10ServiceId);

hm10CharId = "0000FFE1-0000-1000-8000-00805F9B34FB";

ptrHM10Char = new QBluetoothUuid(hm10CharId);



ptrQBluetoothDeviceInfo = new QBluetoothDeviceInfo(QBluetoothAddress(hm10Address ),hm10Name,0);

qDebug() << "created ptrQBluetoothDeviceInfo Object :) ";

m_control = new QLowEnergyController(*ptrQBluetoothDeviceInfo, this);

m_control->connectToDevice();

m_service=0;


connect(m_control, SIGNAL(connected()),
this, SLOT(deviceConnected()));

connect(m_control, SIGNAL(error(QLowEnergyController::Error)),
this, SLOT(controllerError(QLowEnergyController::Error)) );


connect(m_control, SIGNAL(serviceDiscovered(QBluetoothUuid)),
this, SLOT(serviceDiscovered(QBluetoothUuid)));


connect(m_control, SIGNAL(discoveryFinished()),
this, SLOT(serviceScanDone()));


connect(m_control, SIGNAL(disconnected()),
this, SLOT(deviceDisconnected()));

}


void leConnection::deviceConnected()
{
qDebug() << "Success Device Connected ....... " << ptrQBluetoothDeviceInfo->name();

m_control->discoverServices();

}

void leConnection::controllerError(QLowEnergyController ::Error error)
{
qDebug() << "Cannot connect to remote device.";

qDebug() << "Controller Error:" << error;
}


void leConnection::serviceDiscovered(const QBluetoothUuid &gatt)

{
qDebug() << "service" << gatt.toString();

}



void leConnection::connectToService(const QString &address)

{


}


void leConnection::serviceScanDone()
{


qDebug() << "Services Scan Done for ..... " << ptrHM10serial->toString();


m_service = m_control->createServiceObject(*ptrHM10serial,this);

m_service->discoverDetails();


connect(m_service, SIGNAL(characteristicChanged(QLowEnergyCharacteris tic,QByteArray)),
this, SLOT(updateSerialValue(QLowEnergyCharacteristic,QB yteArray)));


connect(m_service, SIGNAL(stateChanged(QLowEnergyService::ServiceStat e)),
this, SLOT(serviceStateChanged(QLowEnergyService::Servic eState)));


connect(m_service, SIGNAL(descriptorWritten(QLowEnergyDescriptor,QByt eArray)),
this, SLOT(confirmedDescriptorWrite(QLowEnergyDescriptor ,QByteArray)));
}


void leConnection::serviceStateChanged(QLowEnergyServic e::ServiceState s)

{

qDebug() << "gets to here 4 " << s;

switch (s) {

case QLowEnergyService::ServiceDiscovered:

{


const QLowEnergyCharacteristic hm10Char = m_service->characteristic(*ptrHM10Char);


qDebug() << hm10Char.value() << "lllllllll";


const QLowEnergyDescriptor m_notificationDesc =

hm10Char.descriptor(QBluetoothUuid::ClientCharacte risticConfiguration);

if (m_notificationDesc.isValid())

{
qDebug() << "gets to here 4yyyyyyyyyyyyyyyyyyy ";

m_service->writeDescriptor(m_notificationDesc, QByteArray::fromHex("0100"));

}

break;


}
default:

//nothing for now
break;
}

}



void leConnection::updateSerialValue(const QLowEnergyCharacteristic &c, const QByteArray &value)


{

qDebug() << c.uuid();


qDebug() << value; // part victron line

}




void leConnection::confirmedDescriptorWrite(const QLowEnergyDescriptor &d, const QByteArray &value)
{

qDebug() << "gets to here 6 " << value ;

if (value == QByteArray("0100"))
{
qDebug() << " testing";
}


if (d.isValid() && d == m_notificationDesc && value == QByteArray("0000"))

{
//disabled notifications -> assume disconnect intent

m_control->disconnectFromDevice();

delete m_service;

m_service = 0;
}

}



void leConnection::deviceDisconnected()
{

qDebug() << "Remote device disconnected";
}


leConnection::~leConnection()
{

}