Getting - Controller Error: QLowEnergyController::ConectionError

[sarthak031]

HI,
I am new in the Qt Desktop App Development. I am using the QtBluetooth library in my desktop app but when i am trying to connect my BLE device I am getting the error (Controller Error: QLowEnergyController::ConectionError). And I am able to connect my BLE device with other desktop apps. So please help me with this.

[Pl45m4]

@sarthak031

Since we are not clairvoyant, you need to provide some more information.

[sarthak031]

@Pl45m4 I have a BLE-based Hardware device for which I want to make the Desktop app to connect the BLE device and read the data through it. I am using visual studio 2019 for the app development using the Qt opensource Bluetooth library.

So I write this code

BLEInterface::BLEInterface(QObject* parent) : QObject(parent),
m_currentDevice(0),
m_control(0),
m_service(0),
m_readTimer(0),
m_connected(false),
m_currentService(0)
{
m_deviceDiscoveryAgent = new QBluetoothDeviceDiscoveryAgent(this);

connect(m_deviceDiscoveryAgent, SIGNAL(deviceDiscovered(const QBluetoothDeviceInfo&)),
	this, SLOT(addDevice(const QBluetoothDeviceInfo&)));
connect(m_deviceDiscoveryAgent, SIGNAL(error(QBluetoothDeviceDiscoveryAgent::Error)),
	this, SLOT(onDeviceScanError(QBluetoothDeviceDiscoveryAgent::Error)));
connect(m_deviceDiscoveryAgent, SIGNAL(finished()), this, SLOT(onScanFinished()));

}

BLEInterface::~BLEInterface()
{
qDeleteAll(m_devices);
m_devices.clear();
}

void BLEInterface::scanDevices()
{
m_devicesNames.clear();
qDeleteAll(m_devices);
m_devices.clear();
emit devicesNamesChanged(m_devicesNames);
m_deviceDiscoveryAgent->start();
m_deviceDiscoveryAgent->setLowEnergyDiscoveryTimeout(10000);
//emit statusInfoChanged("Scanning for devices...", true);
}

void BLEInterface::read() {
if (m_service && m_readCharacteristic.isValid())
m_service->readCharacteristic(m_readCharacteristic);
}

void BLEInterface::waitForWrite() {
QEventLoop loop;
connect(m_service, SIGNAL(characteristicWritten(QLowEnergyCharacteristic, QByteArray)),
&loop, SLOT(quit()));
loop.exec();
}

void BLEInterface::write(const QByteArray& data)
{
qDebug() << "BLEInterface::write: " << data;
if (m_service && m_writeCharacteristic.isValid()) {
if (data.length() > CHUNK_SIZE) {
int sentBytes = 0;
while (sentBytes < data.length()) {
m_service->writeCharacteristic(m_writeCharacteristic,
data.mid(sentBytes, CHUNK_SIZE),
m_writeMode);
sentBytes += CHUNK_SIZE;
if (m_writeMode == QLowEnergyService::WriteWithResponse) {
waitForWrite();
if (m_service->error() != QLowEnergyService::NoError)
return;
}
}

	}
	else
		m_service->writeCharacteristic(m_writeCharacteristic, data, m_writeMode);
}

}

void BLEInterface::addDevice(const QBluetoothDeviceInfo& device)
{
if (device.coreConfigurations() & QBluetoothDeviceInfo::LowEnergyCoreConfiguration)
{
qWarning() << "Discovered LE Device name: " << device.name() << " Address: "
<< device.address().toString();
m_devicesNames.append(device.name());
DeviceInfo* dev = new DeviceInfo(device);
m_devices.append(dev);
emit devicesNamesChanged(m_devicesNames);
//emit printf("Low Energy device found. Scanning for more...");
}
//...
}

void BLEInterface::onScanFinished()
{
if (m_devicesNames.size() == 0)
/emit/ printf("No Low Energy devices found");
}

void BLEInterface::onDeviceScanError(QBluetoothDeviceDiscoveryAgent::Error error)
{
if (error == QBluetoothDeviceDiscoveryAgent::PoweredOffError)
/emit/ printf("The Bluetooth adaptor is powered off, power it on before doing discovery.");
else if (error == QBluetoothDeviceDiscoveryAgent::InputOutputError)
/emit/ printf("Writing or reading from the device resulted in an error.");
else
/emit/ printf("An unknown error has occurred.");
}

void BLEInterface::connectCurrentDevice()
{
if (m_devices.isEmpty())
return;

if (m_control)
{
	m_control->disconnectFromDevice();
	delete m_control;
	m_control = 0;

}
m_control = new QLowEnergyController(m_devices[m_currentDevice]->getDevice(), this);
connect(m_control, SIGNAL(connected()),
	this, SLOT(onDeviceConnected()));
connect(m_control, SIGNAL(error(QLowEnergyController::Error)),
	this, SLOT(onControllerError(QLowEnergyController::Error)));
connect(m_control, SIGNAL(disconnected()),
	this, SLOT(onDeviceDisconnected()));
connect(m_control, SIGNAL(serviceDiscovered(QBluetoothUuid)),
	this, SLOT(onServiceDiscovered(QBluetoothUuid)));
connect(m_control, SIGNAL(discoveryFinished()),
	this, SLOT(onServiceScanDone()));


m_control->connectToDevice();

}

void BLEInterface::onDeviceConnected()
{
m_servicesUuid.clear();
m_services.clear();
setCurrentService(-1);
emit servicesChanged(m_services);
m_control->discoverServices();
}

void BLEInterface::onDeviceDisconnected()
{
update_connected(false);
// emit statusInfoChanged("Service disconnected", false);
qWarning() << "Remote device disconnected";
}

void BLEInterface::onServiceDiscovered(const QBluetoothUuid& gatt)
{
Q_UNUSED(gatt)
/* emit*/ printf("Service discovered. Waiting for service scan to be done...");
}

void BLEInterface::onServiceScanDone()
{
m_servicesUuid = m_control->services();
if (m_servicesUuid.isEmpty())
/* emit*/ printf("Can't find any services.");
else {
m_services.clear();
foreach(auto uuid, m_servicesUuid)
m_services.append(uuid.toString());
emit servicesChanged(m_services);
m_currentService = -1;// to force call update_currentService(once)
setCurrentService(0);
/* emit*/ printf("All services discovered.");
}
}

void BLEInterface::disconnectDevice()
{
m_readTimer->deleteLater();
m_readTimer = NULL;

if (m_devices.isEmpty()) {
	return;
}

//disable notifications
if (m_notificationDesc.isValid() && m_service) {
	m_service->writeDescriptor(m_notificationDesc, QByteArray::fromHex("0000"));
}
else {
	m_control->disconnectFromDevice();
	delete m_service;
	m_service = 0;
}

}

void BLEInterface::onControllerError(QLowEnergyController::Error error)
{
/* emit*/ printf("Cannot connect to remote device.");
qWarning() << "Controller Error:" << error;
}

void BLEInterface::onCharacteristicChanged(const QLowEnergyCharacteristic& c,
const QByteArray& value)
{
Q_UNUSED(c)
qDebug() << "Characteristic Changed: " << value;
// emit dataReceived(value);
}
void BLEInterface::onCharacteristicWrite(const QLowEnergyCharacteristic& c,
const QByteArray& value)
{
Q_UNUSED(c)
qDebug() << "Characteristic Written: " << value;
}

void BLEInterface::update_currentService(int indx)
{
delete m_service;
m_service = 0;

if (indx >= 0 && m_servicesUuid.count() > indx) {
	m_service = m_control->createServiceObject(
		m_servicesUuid.at(indx), this);
}

if (!m_service) {
	/* emit*/ printf("Service not found.");
	return;
}

connect(m_service, SIGNAL(stateChanged(QLowEnergyService::ServiceState)),
	this, SLOT(onServiceStateChanged(QLowEnergyService::ServiceState)));
connect(m_service, SIGNAL(characteristicChanged(QLowEnergyCharacteristic, QByteArray)),
	this, SLOT(onCharacteristicChanged(QLowEnergyCharacteristic, QByteArray)));
connect(m_service, SIGNAL(characteristicRead(QLowEnergyCharacteristic, QByteArray)),
	this, SLOT(onCharacteristicRead(QLowEnergyCharacteristic, QByteArray)));
connect(m_service, SIGNAL(characteristicWritten(QLowEnergyCharacteristic, QByteArray)),
	this, SLOT(onCharacteristicWrite(QLowEnergyCharacteristic, QByteArray)));
connect(m_service, SIGNAL(error(QLowEnergyService::ServiceError)),
	this, SLOT(serviceError(QLowEnergyService::ServiceError)));

if (m_service->state() == QLowEnergyService::DiscoveryRequired) {
	/* emit*/ printf("Connecting to service...");
	m_service->discoverDetails();
}
else
	searchCharacteristic();

}
void BLEInterface::onCharacteristicRead(const QLowEnergyCharacteristic& c,
const QByteArray& value) {
Q_UNUSED(c)
qDebug() << "Characteristic Read: " << value;
//emit dataReceived(value);
}

void BLEInterface::searchCharacteristic() {
if (m_service) {
foreach(QLowEnergyCharacteristic c, m_service->characteristics()) {
if (c.isValid()) {
if (c.properties() & QLowEnergyCharacteristic::WriteNoResponse ||
c.properties() & QLowEnergyCharacteristic::Write) {
m_writeCharacteristic = c;
update_connected(true);
if (c.properties() & QLowEnergyCharacteristic::WriteNoResponse)
m_writeMode = QLowEnergyService::WriteWithoutResponse;
else
m_writeMode = QLowEnergyService::WriteWithResponse;

			}
			if (c.properties() & QLowEnergyCharacteristic::Read) {
				m_readCharacteristic = c;
				if (!m_readTimer) {
					m_readTimer = new QTimer(this);
					connect(m_readTimer, &QTimer::timeout, this, &BLEInterface::read);
					m_readTimer->start(
					);
				}
			}
			m_notificationDesc = c.descriptor(
				QBluetoothUuid::ClientCharacteristicConfiguration);
			if (m_notificationDesc.isValid()) {
				m_service->writeDescriptor(m_notificationDesc, QByteArray::fromHex("0100"));
			}
		}
	}
}

}

void BLEInterface::onServiceStateChanged(QLowEnergyService::ServiceState s)
{
qDebug() << "serviceStateChanged, state: " << s;
if (s == QLowEnergyService::ServiceDiscovered) {
searchCharacteristic();
}
}
void BLEInterface::serviceError(QLowEnergyService::ServiceError e)
{
qWarning() << "Service error:" << e;
}

but I am getting the Controller Error: QLowEnergyController::ConectionError while I am trying to connect my BLE Device.

[Pl45m4]

@sarthak031 said in Getting - Controller Error: QLowEnergyController::ConectionError:

but I am getting the Controller Error: QLowEnergyController::ConectionError while I am trying to connect my BLE Device.

Where exactly? The deviceDiscovery works?

[sarthak031]

@Pl45m4
yes, Device discovery is working correctly but when I am trying to connect the device I get this error.

[Pl45m4]

@sarthak031

You are using this example (https://github.com/Gawhary/BLE-Tester), aren't you?
Where exactly the error occurs (use debugger)? Is your device BLE ready?

Test your connection using the official BTLE examples

• https://doc.qt.io/qt-5/qtbluetooth-le-overview.html#using-qt-bluetooth-low-energy-api
• https://doc.qt.io/qt-5/qtbluetooth-lowenergyscanner-example.html