【发布时间】：2021-08-15 16:03:55
【问题描述】：
我尝试在需要心脏频率的 Qt creator(C++) 上开发一个 windows 10 软件。我买了下面的传感器，通过蓝牙传输数据（BLE：蓝牙低能量）：
但是当我尝试读取值时，我有一个空缓冲区。
传感器在安卓应用程序上正常工作（在 Play 商店中）
我的代码：
初始化：确定
TWindowsStatistique::TWindowsStatistique(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::TWindowsStatistique)
{
QBluetoothDeviceDiscoveryAgent *discoveryAgent = new QBluetoothDeviceDiscoveryAgent(this);
connect(discoveryAgent, SIGNAL(deviceDiscovered(QBluetoothDeviceInfo)),this, SLOT(deviceDiscovered(QBluetoothDeviceInfo)));
discoveryAgent->start();
}
获取蓝牙设备列表：OK
void TWindowsStatistique::deviceDiscovered(const QBluetoothDeviceInfo &device)
{
if(device.name()=="Decathlon Dual HR")
{
m_device=device;
if (!controller)
{
controller = QLowEnergyController::createCentral(device);
connect(controller, &QLowEnergyController::connected,this, &TWindowsStatistique::deviceConnected);
connect(controller, QOverload<QLowEnergyController::Error>::of(&QLowEnergyController::error),this, &TWindowsStatistique::errorReceived);
connect(controller, &QLowEnergyController::disconnected,this, &TWindowsStatistique::deviceDisconnected);
}
controller->connectToDevice();
}
}
获取服务列表：确定
void TWindowsStatistique::deviceConnected()
{
connect(controller, &QLowEnergyController::serviceDiscovered,this, &TWindowsStatistique::addLowEnergyService);
connect(controller, &QLowEnergyController::discoveryFinished,this, &TWindowsStatistique::serviceScanDone);
controller->discoverServices();
}
void TWindowsStatistique::addLowEnergyService(const QBluetoothUuid &newService)
{
QLowEnergyService *service = controller->createServiceObject(newService);
if (!service) return;
if(service->serviceName()=="Heart Rate")
{
heart_rate_service=service;
}
}
void TWindowsStatistique::serviceScanDone()
{
if(heart_rate_service!=NULL)
{
connect(heart_rate_service, &QLowEnergyService::stateChanged, this, &TWindowsStatistique::serviceDetailsDiscovered);
heart_rate_service->discoverDetails();
}
}
获取特征列表：OK 有心率数据：NOK
void TWindowsStatistique::serviceDetailsDiscovered(QLowEnergyService::ServiceState newState)
{
const QList<QLowEnergyCharacteristic> chars = heart_rate_service->characteristics();
for (int i=0;i<chars.size();i++)
{
QLowEnergyCharacteristic tmp_char=chars.at(i);
if(tmp_char.name()=="Heart Rate Measurement")//the code go in : **OK**
{
qDebug() << "carac value" << chars.at(i).value().toHex();//return a empty buffer : **NOK**
//test by using a class with notify requerement : **NOK**
// in THeartRateCharacteristic.h: Q_PROPERTY(QString characteristicValue READ getValue NOTIFY characteristicChanged)
heart_rate_characteristic = new THeartRateCharacteristic(tmp_char);
//test by using characteristicChanged : slot isn't call : **NOK**
connect(heart_rate_characteristic, SIGNAL(characteristicChanged()), this, SLOT(heart_rate_update()));
//try tu use readCharacteristic : the sensor doesn't answer **NOK**
heart_rate_service->readCharacteristic(tmp_char);
//Test to put notification flag to 1 : **heart rate data stay empty**
for(int j=0;j<chars.at(i).descriptors().size();j++)
{
if(chars.at(i).descriptors().at(j).name()=="Client Characteristic Configuration")
{
QByteArray tmp=chars.at(i).descriptors().at(j).value();
tmp[1]=0;
tmp[0]=1;
if(chars.at(i).descriptors().at(j).value().compare(tmp)!=0)
{
connect(heart_rate_service, &QLowEnergyService::descriptorWritten,this, &TWindowsStatistique::descriptorWritten_slot);
connect(heart_rate_service, SIGNAL(error(QLowEnergyService::ServiceError)),this, SLOT(service_error_slot(QLowEnergyService::ServiceError)));
heart_rate_service->writeDescriptor(chars.at(i).descriptors().at(j),tmp);
}
}
}
}
}
}
void TWindowsStatistique::timer_1s_timeout()
{
if(heart_rate_characteristic)
{
qDebug() << "timer: data value:" << heart_rate_characteristic->getValue();//return a empty buffer : **NOK**
}
}
【问题讨论】：
-
新：我测试了其他数据并且可以读取它们。与心率的区别在于它的类型是“通知”而不是“读取”。我看到 BLE 通知出现问题：[forum.qt.io/topic/122098/…我尝试在 .pro 中使用 exe 路径的“BLUETOOTH_FORCE_DBUS_LE_VERSION=5.41 /path”，但它什么也没做。
-
“测试将通知标志置为 1：心率数据保持为空”是什么意思？将 CCCD 设置为 1 后，考虑到您的代码，只要通知新的 HRM 值，就应该执行
heart_rate_update()。不是这样吗？
标签： c++ qt bluetooth-lowenergy heartrate