How to write to BLE Characteristic?

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Please refer my code

Code:

#include "bluetoothupdater.h"
 
BluetoothUpdater::BluetoothUpdater()
{
    QBluetoothDeviceDiscoveryAgent* discovery = new QBluetoothDeviceDiscoveryAgent();
 
    connect(discovery, &QBluetoothDeviceDiscoveryAgent::deviceDiscovered, [&] (const QBluetoothDeviceInfo &device)
    {
        if(device.name() == "Targ")
        {
            qDebug() << "Found new device:" << device.name();
            ptrQBluetoothDeviceInfo = new QBluetoothDeviceInfo(QBluetoothAddress(device.address()), device.name(), 0);
            m_control = new QLowEnergyController(*ptrQBluetoothDeviceInfo);
            m_control->connectToDevice();
            m_control->discoverServices();
            //connect(m_control, &QLowEnergyService::stateChanged, this, &BluetoothUpdater::service    serviceDiscovered, this, &BluetoothUpdater::serviceDiscovered);
            connect(m_control, &QLowEnergyController::serviceDiscovered, this, &BluetoothUpdater::serviceDiscovered);
            connect(m_control, &QLowEnergyController::discoveryFinished, this, &BluetoothUpdater::serviceScanDone);
        }
    });
 
    //connect(discovery, &QBluetoothDeviceDiscoveryAgent::deviceDiscovered, this, &BluetoothUpdater::addDevice);
    discovery->setLowEnergyDiscoveryTimeout(5000);
    discovery->start(QBluetoothDeviceDiscoveryAgent::LowEnergyMethod);
}
 
void BluetoothUpdater::serviceScanDone()
{
    qDebug() << "Service scan done.";
 
    if (m_foundHeartRateService)
    {
        qDebug() << m_foundHeartRateService;
        m_service = m_control->createServiceObject(QBluetoothUuid(DFUService));
        qDebug() << m_service;
    }
 
    if (m_service)
    {
        qDebug() << "DFU Service found";
        m_service->discoverDetails();
        connect(m_service, &QLowEnergyService::stateChanged, this, &BluetoothUpdater::serviceStateChanged);
        connect(m_service, &QLowEnergyService::characteristicChanged, this, &BluetoothUpdater::updateValue);
        connect(m_service, &QLowEnergyService::descriptorWritten, this, &BluetoothUpdater::confirmedDescriptorWrite);
    }
    else
    {
        qDebug() << "DFU Service not found.";
    }
}
 
void BluetoothUpdater::serviceDiscovered(const QBluetoothUuid &gatt)
{
    if (gatt == QBluetoothUuid(DFUService))
    {
        qDebug() << "DFU service discovered.";
        m_foundHeartRateService = true;
    }
}
 
void BluetoothUpdater::serviceStateChanged(QLowEnergyService::ServiceState state)
{
    if(state == QLowEnergyService::ServiceDiscovered)
    {
        ControlPointChar = m_service->characteristic(QBluetoothUuid(ControlPointUUID));
        if(ControlPointChar.isValid())
        {
            qDebug() << "Control Point Characteristic Found";           
            m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("0601"), QLowEnergyService::WriteWithResponse);
        }
        else
        {
            qDebug() << "Control Point Characteristic Not Found";
        }
        ControlPointDesc = ControlPointChar.descriptor(QBluetoothUuid::ClientCharacteristicConfiguration);
        if (ControlPointDesc.isValid())
        {
            qDebug() << "Descriptor";
            m_service->writeDescriptor(ControlPointDesc, QByteArray::fromHex("0100"));
        }
    }
}
 
void BluetoothUpdater::updateValue(const QLowEnergyCharacteristic &c, const QByteArray &value)
{
    qDebug() << "updateValue, c.uuid:" << c.uuid();
    qDebug() << "updateValue, value:" << value;
}
 
void BluetoothUpdater::confirmedDescriptorWrite(const QLowEnergyDescriptor &d, const QByteArray &value)
{
    qDebug() << "confirmedDescriptorWrite:" << value;
    if (d.isValid() && d == ControlPointDesc && value == QByteArray::fromHex("0000"))
    {
        qDebug() << "Inside confirmedDescriptorWrite";
        m_control->disconnectFromDevice();
        delete m_service;
        m_service = nullptr;
    }
}

This line

Code:

m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("0601"), QLowEnergyService::WriteWithResponse);

does not work

20th August 2019, 22:27
d_stranz

Re: How to write to BLE Characteristic?

Quote:

does not work

Doesn't compile?
Doesn't link?
Doesn't execute?
Doesn't produce the desired result?
Or is just tired and didn't want to work?

Sorry, I can't be of more help, but my crystal ball is out of service today.

Re: How to write to BLE Characteristic?

My bad!!

Code:

#include "bluetoothupdater.h"
 
BluetoothUpdater::BluetoothUpdater()
{
    QBluetoothDeviceDiscoveryAgent* discovery = new QBluetoothDeviceDiscoveryAgent();
 
    connect(discovery, &QBluetoothDeviceDiscoveryAgent::deviceDiscovered, [&] (const QBluetoothDeviceInfo &device)
    {
        if(device.name() == "Targ")
        {
            qDebug() << "Found new device:" << device.name();
            ptrQBluetoothDeviceInfo = new QBluetoothDeviceInfo(QBluetoothAddress(device.address()), device.name(), 0);
            m_control = new QLowEnergyController(*ptrQBluetoothDeviceInfo);
            m_control->connectToDevice();
            m_control->discoverServices();
            connect(m_control, &QLowEnergyController::serviceDiscovered, this, &BluetoothUpdater::serviceDiscovered);
            connect(m_control, &QLowEnergyController::discoveryFinished, this, &BluetoothUpdater::serviceScanDone);
        }
    });
 
    discovery->setLowEnergyDiscoveryTimeout(5000);
    discovery->start(QBluetoothDeviceDiscoveryAgent::LowEnergyMethod);
}
 
void BluetoothUpdater::serviceScanDone()
{
    qDebug() << "Service scan done.";
 
    if (m_foundHeartRateService)
    {
        qDebug() << m_foundHeartRateService;
        m_service = m_control->createServiceObject(QBluetoothUuid(DFUService));
        qDebug() << m_service;
    }
 
    if (m_service)
    {
        qDebug() << "DFU Service found";
        m_service->discoverDetails();
        connect(m_service, &QLowEnergyService::stateChanged, this, &BluetoothUpdater::serviceStateChanged);
        connect(m_service, &QLowEnergyService::characteristicChanged, this, &BluetoothUpdater::updateValue);
        connect(m_service, &QLowEnergyService::descriptorWritten, this, &BluetoothUpdater::confirmedDescriptorWrite);
    }
    else
    {
        qDebug() << "DFU Service not found.";
    }
}
 
void BluetoothUpdater::serviceDiscovered(const QBluetoothUuid &gatt)
{
    if (gatt == QBluetoothUuid(DFUService))
    {
        qDebug() << "DFU service discovered.";
        m_foundHeartRateService = true;
    }
}
 
void BluetoothUpdater::serviceStateChanged(QLowEnergyService::ServiceState state)
{
    if(state == QLowEnergyService::ServiceDiscovered)
    {
        ControlPointChar = m_service->characteristic(QBluetoothUuid(ControlPointUUID));
        if(ControlPointChar.isValid())
        {
            qDebug() << "Control Point Characteristic Found";
            ControlPointDesc = ControlPointChar.descriptor(QBluetoothUuid::ClientCharacteristicConfiguration);
            if (ControlPointDesc.isValid())
            {
                qDebug() << "Control Point Descriptor";
                m_service->writeDescriptor(ControlPointDesc, QByteArray::fromHex("0100"));
            }
            WriteControl = 1;
        }
        else
        {
            qDebug() << "Control Point Characteristic Not Found";
            WriteControl = 0;
        }
 
        PacketChar = m_service->characteristic(QBluetoothUuid(PacketUUID));
        if(PacketChar.isValid())
        {
            qDebug() << "Packet Characteristic Found";
            WritePacket = 1;
        }
        else
        {
            qDebug() << "Packet Characteristic Not Found";
            WritePacket = 0;
        }
 
        if((WriteControl == 1) && (WritePacket == 1))
        {
            QFile InitFS("C:/Users/Sonal/Documents/data_glove_editor/res/firmwareUpdate/app.dat"); // Init dat file
            if (!InitFS.open(QIODevice::ReadOnly))
            {
                qDebug() << "Init file cannot be opened";
                return;
            }
            else
            {
                qDebug() << "File opened";
 
                m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("0601"), QLowEnergyService::WriteWithResponse);
                QThread::msleep(100);
 
                m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("01018E000000"), QLowEnergyService::WriteWithResponse);
                QThread::msleep(100);
 
                qDebug() << "Init File Length = " << InitFS.size();
 
                int NoOfInitFilePackets = InitFS.size() / BLEPacketLength;
                qDebug() << "No Of Init File Packets = " << NoOfInitFilePackets;
 
                int InitFileBytesRemaining = InitFS.size() % BLEPacketLength;
                qDebug() << "Init File Bytes Remaining = " << InitFileBytesRemaining;
 
                for (InitFilePacketCounter = 0, InitFilePointer = 0; InitFilePacketCounter < NoOfInitFilePackets; InitFilePacketCounter++, InitFilePointer += 20)
                {
                    InitFS.seek(InitFilePointer);
                    InitBuffer = InitFS.read(BLEPacketLength);
                    //qDebug() << "InitFilePointer = " << InitFilePointer;
                    qDebug() << "InitBuffer = " << InitBuffer.toHex();
                    m_service->writeCharacteristic(PacketChar, QByteArray::fromHex(InitBuffer), QLowEnergyService::WriteWithoutResponse);
                    QThread::msleep(100);
                }
 
                InitFS.seek(InitFilePointer);
                InitFileBytesLeft = InitFS.read(InitFileBytesRemaining);
                qDebug() << "InitFileBytesLeft = " << InitFileBytesLeft.toHex();
 
                m_service->writeCharacteristic(PacketChar, QByteArray::fromHex(InitFileBytesLeft), QLowEnergyService::WriteWithoutResponse);
                QThread::msleep(100);
 
                m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("03"), QLowEnergyService::WriteWithResponse);
                QThread::msleep(100);
 
                m_service->writeCharacteristic(ControlPointChar, QByteArray::fromHex("04"), QLowEnergyService::WriteWithResponse);
                QThread::msleep(100);
            }
        }
    }
}
 
void BluetoothUpdater::updateValue(const QLowEnergyCharacteristic &c, const QByteArray &value)
{
    //qDebug() << "updateValue, c.uuid:" << c.uuid();
    qDebug() << "                                               updateValue, value:" << value.toHex();
}
 
void BluetoothUpdater::confirmedDescriptorWrite(const QLowEnergyDescriptor &d, const QByteArray &value)
{
    qDebug() << "confirmedDescriptorWrite:" << value.toHex();
    if (d.isValid() && d == ControlPointDesc && value == QByteArray::fromHex("0000"))
    {
        qDebug() << "Inside confirmedDescriptorWrite";
        m_control->disconnectFromDevice();
        delete m_service;
        m_service = nullptr;
    }
}

I moved a step further. New code is pasted above. I'm not getting responses for the last 2 "m_service->writeCharacteristic(ControlPointChar,....". If I comment "m_service->writeCharacteristic(PacketChar, ... ", then I get responses for "m_service->writeCharacteristic(ControlPointChar, ...". I always get responses for first 2 "m_service->writeCharacteristic(ControlPointChar, ...". Is there some problem with creating the handles to 2 different characteristics using "m_service->writeCharacteristic"?? When I say I'm getting responses, it means that "updateValue" is being called each time I write to ControlPointChar. What am I missing here? Why multiple writes to multiple characteristics is failing??