【QT问题解决】QT Modbus rtu 拖动主界面时modbus的槽函数无法响应的解决方案

问题 Modbus放在主线程，界面事件会阻塞信号传输

在使用QT5.14.2时 使用QT自带的QModbusClient类实现对一个力传感器的数据读取。本人为了测试就将modbus读取逻辑等都写在主线程中，但是本人采用modbus异步通讯的方式，给从站发一个读取数据的信号（sendReadRequest），然后使用信号槽等待从站回复数据（readSerialForceData）。这种方式的好处是不会阻塞主线程。

但是！本人发现一个问题，就是在我拖动主界面的时候，modbus通讯就停止了！当我松开鼠标的时候，modbus正常通讯！目前还不知道为什么会这样，猜测是鼠标事件影响了modbus的信号槽机制。但是我试了一下，其他的槽函数都是能正常触发的，比如定时器之类。在我拖动界面的时候，UI界面也可以正常的刷新。只有modbus被阻塞了。

void MainWindow::on_readRequest()
{
    // 读取寄存器
    QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters,0,1);
    if (auto *reply = modbusDevice->sendReadRequest(readUnit, 1))
    {
        if (!reply->isFinished())
            connect(reply, &QModbusReply::finished, this, &MainWindow::readSerialForceData);
        else
            delete reply; // broadcast replies return immediately
    }
    else
    {
        //底部状态栏显示
        ui->statusBar->showMessage(tr("Read error: ") + modbusDevice->errorString(), 5000);
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

void MainWindow::readSerialForceData()
{

    auto reply = qobject_cast<QModbusReply *>(sender());
    if (!reply)
        return;

    if (reply->error() == QModbusDevice::NoError)
    {
        const QModbusDataUnit unit = reply->result();
        //遍历数据单元的值
        for (int i = 0, total = int(unit.valueCount()); i < total; ++i)
        {
            qint16 sValue = static_cast<qint16>(unit.value(i));
            forceData_Temp = sValue/10.0;
            const QString entry = tr("Address: %1, Value: %2").arg(unit.startAddress() + i).arg(QString::number(sValue));
            ui->textBrowser_Log->append(entry);
        }
    }
    else if (reply->error() == QModbusDevice::ProtocolError)
    {
        statusBar()->showMessage(tr("Read response error: %1 (Mobus exception: 0x%2)").
                                 arg(reply->errorString()).
                                 arg(reply->rawResult().exceptionCode(), -1, 16), 5000);
    }
    else
    {
        statusBar()->showMessage(tr("Read response error: %1 (code: 0x%2)").
                                 arg(reply->errorString()).
                                 arg(reply->error(), -1, 16), 5000);
    }

    reply->deleteLater();
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34

解决方案 将modbus放在子线程实现

经过测试，发现将modbus放在子线程中，通过信号槽与主线程进行通讯，将数据保存成静态变量或者全局变量，即可解决问题。

这里新建一个serialThread 类用
.h文件

class serialThread : public QObject
{
    Q_OBJECT
public:
    serialThread(QObject *parent = Q_NULLPTR);
    ~serialThread();

    QModbusClient *modbusDevice = nullptr;

    QDateTime startTime;
    QDateTime endTime;
    double intervalTime = 0;//串口数据间隔时间
    double intervalTime_Last=0;
    //数据采集定时器
    QTimer *pollTimer;//串口数据读取定时器

signals:
    void sig_connectSerialFinished(bool flag);
    void sig_disconnectSerialFinished(bool flag);

public slots:
    void startThread();
    void on_connectSerial();
    void on_disconnectSerial();
    void on_startReadData();
    void on_stopReadData();
    void on_readRequest();
    void on_readRequestFinished();
};

#endif // SERIALTHREAD_H
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

.cpp文件

#include "serialthread.h"

serialThread::serialThread(QObject *parent ) : QObject(parent)
{
    qDebug()<<"串口线程构造函数:"<<QThread::currentThreadId();
}

serialThread::~serialThread()
{
    //退出串口
    if (modbusDevice)
    {
        modbusDevice->disconnectDevice();
    }

    delete modbusDevice;

}

void serialThread::startThread()
{
    qDebug()<<"串口线程成员函数 startThread :"<<QThread::currentThreadId();
    modbusDevice = new QModbusRtuSerialMaster(this);
}

void serialThread::on_connectSerial()
{

    qDebug()<<"串口线程成员函数 on_connectSerial :"<<QThread::currentThreadId();
    QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁

    //设置串口号
    modbusDevice->setConnectionParameter(QModbusDevice::SerialPortNameParameter,ForceSensorGlobal::SeriComName);
    //设置波特率
    modbusDevice->setConnectionParameter(QModbusDevice::SerialBaudRateParameter,ForceSensorGlobal::BaudRate);
    //设置数据位
    modbusDevice->setConnectionParameter(QModbusDevice::SerialDataBitsParameter,ForceSensorGlobal::DataBits);
    //设置奇偶检验
    switch(ForceSensorGlobal::ParityID)
    {
    case 0: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::NoParity);break;
    case 1: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::EvenParity);break;
    case 2: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::OddParity);break;
    case 3: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::SpaceParity);break;
    case 4: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::MarkParity);break;
    default: break;
    }
    //设置停止位
    switch(ForceSensorGlobal::StopBitsID)
    {
    case 0: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::OneStop);break;
    case 1: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::OneAndHalfStop);break;
    case 2: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::TwoStop);break;
    default: break;
    }
    //设置执行请求时间
    modbusDevice->setTimeout(1000);
    //设置执行请求次数
    modbusDevice->setNumberOfRetries(3);

    //连接串口 并发送成功与否标志
    emit sig_connectSerialFinished(modbusDevice->connectDevice());

    pollTimer = new QTimer;
    pollTimer->setTimerType(Qt::PreciseTimer);//精确定时
    pollTimer->setInterval(ForceSensorGlobal::IntervalTime);
    connect(pollTimer,&QTimer::timeout, this, &serialThread::on_readRequest);

}

void serialThread::on_disconnectSerial()
{
    modbusDevice->disconnectDevice();
    emit sig_disconnectSerialFinished(true);

}

void serialThread::on_startReadData()
{
    QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁

    //清空一下数据 方便再次存储
    ForceSensorGlobal:: recordData.clear();
    QVector<double> vectorTemp;
    for (int i = 0; i < 2; i++)
    {
        ForceSensorGlobal::recordData.append(vectorTemp);
    }
    startTime = QDateTime::currentDateTime();//获取开始时间
    pollTimer->setInterval(ForceSensorGlobal::IntervalTime);
    pollTimer->start();
    qDebug() <<"子线程 on_startReadData ";
}

void serialThread::on_stopReadData()
{
    pollTimer->stop();
    qDebug() <<"子线程 on_stopReadData ";
}

void serialThread::on_readRequest()
{
    // 读取寄存器
    QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters,0,1);
    if (auto *reply = modbusDevice->sendReadRequest(readUnit, 1))
    {
        if (!reply->isFinished())
            connect(reply, &QModbusReply::finished, this, &serialThread::on_readRequestFinished);
        else
            reply->deleteLater(); // broadcast replies return immediately
    }
    else
    {
        //读取错误
        qDebug() <<"读取错误: " <<modbusDevice->errorString();
    }
}

void serialThread::on_readRequestFinished()
{
    auto reply = qobject_cast<QModbusReply *>(sender());
    if (!reply)
        return;


    QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁
    if (reply->error() == QModbusDevice::NoError)
    {
        const QModbusDataUnit unit = reply->result();
        //遍历数据单元的值
        for (int i = 0, total = int(unit.valueCount()); i < total; ++i)
        {
            //接受信号的时间
            endTime = QDateTime::currentDateTime();
            intervalTime = startTime.msecsTo(endTime) / 1000.0;

            double now = (intervalTime - intervalTime_Last)*1000.0;
            qDebug() <<now;
            intervalTime_Last = intervalTime;

            //收到的数据是uint16 需转换为int16
            qint16 sValue = static_cast<qint16>(unit.value(i));
            //传感器默认有一位小数，需除以10
            double forceData_Temp = sValue/10.0;
            //将时间 力数据存在到全局变量中
            ForceSensorGlobal::recordData[0].append(intervalTime);
            ForceSensorGlobal::recordData[1].append(forceData_Temp);

        }
    }
    else if (reply->error() == QModbusDevice::ProtocolError)
    {
        //接收到的响应信息是协议错误
        qDebug() <<"接收到的响应信息是协议错误: " <<modbusDevice->errorString();
    }
    else
    {
        //接收到的响应信息是其他错误
        qDebug() <<"接收到的响应信息是其他错误: " <<modbusDevice->errorString();
    }

    reply->deleteLater();
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164

在主线程中通过moveToThread，将modbus放入子线程

主界面.h文件

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QSerialPort>
#include <QtSerialBus>
#include <QModbusDataUnit>
#include <QModbusClient>
#include <QSerialPortInfo>
#include <QMessageBox>
#include <QDebug>
#include <QSettings>
#include "forcesensorglobal.h"
#include "qcustomplot.h"
#include "CurvePlot.h"
#include "serialthread.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    /*************串口通讯线程***************/
    //串口线程
    QThread * mySerialThread;
    //串口操作类
    serialThread  *mySerialModbus;

    /***************定时器**********************/
    QTimer *plotTimer;//
    //UI界面初始化
    void initUI();
    //搜索串口
    void SearchSerialPorts();

signals:
    void sig_connectSerial();
    void sig_disconnectSerial();
    void sig_startReadData();
    void sig_stopReadData();

private slots:
    void on_plotTimerTimeOut();
    void on_pBtn_connectSerial_clicked();
    void on_pBtn_disconnectSerial_clicked();
    //接受子线程 modbus串口连接完成信号
    void on_connectSerialFinished(bool flag);
    //接受子线程 modbus串口断开完成信号
    void on_disconnectSerialFinished(bool flag);
    void on_pBtn_refreshSerial_clicked();
    void on_pBtn_startRead_clicked();
    void on_pBtn_stopRead_clicked();
    void on_pBtn_sendData_clicked();
private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64

主界面.cpp文件

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    initUI();
    /*创建串口线程*/
    mySerialModbus = new serialThread();
    mySerialThread = new QThread;
    mySerialModbus->moveToThread(mySerialThread);
    //线程开始
    mySerialThread->start();
    connect(mySerialThread, &QThread::started, mySerialModbus, &serialThread::startThread);
    connect(mySerialThread, &QThread::finished, mySerialModbus, &QObject::deleteLater);//终止线程时要调用deleteLater槽函数
    connect(mySerialThread, &QThread::finished, mySerialModbus, &QObject::deleteLater);

    /*绘图刷新定时器*/
    plotTimer = new QTimer;
    plotTimer->setInterval(100);
    connect(plotTimer,&QTimer::timeout, this, &MainWindow::on_plotTimerTimeOut);

    /*****************信号槽*********************************/
    //主线->子线程 串口连接信号
    connect(this, &MainWindow::sig_connectSerial, mySerialModbus, &serialThread::on_connectSerial);
    //主线->子线程 串口断开信号
    connect(this, &MainWindow::sig_disconnectSerial, mySerialModbus, &serialThread::on_disconnectSerial);
    //主线->子线程 开始采集信号
    connect(this, &MainWindow::sig_startReadData, mySerialModbus, &serialThread::on_startReadData);
    //主线->子线程 停止采集信号
    connect(this, &MainWindow::sig_stopReadData, mySerialModbus, &serialThread::on_stopReadData);
    //子线程->主线 串口连接完成信号
    connect(mySerialModbus, &serialThread::sig_connectSerialFinished,this,&MainWindow::on_connectSerialFinished);
    //子线程->主线 串口断开完成信号
    connect(mySerialModbus, &serialThread::sig_disconnectSerialFinished,this,&MainWindow::on_disconnectSerialFinished);

void MainWindow::on_pBtn_connectSerial_clicked()
{
    //更新数据
    ForceSensorGlobal::SeriComName = ui->cBox_SeriComName->currentText();
    ForceSensorGlobal::BaudRate = ui->cBox_BaudRate->currentText().toInt();
    ForceSensorGlobal::DataBits = ui->cBox_DataBits->currentText().toInt();
    ForceSensorGlobal::ParityID = ui->cBox_Parity->currentIndex();
    ForceSensorGlobal::StopBitsID = ui->cBox_StopBits->currentIndex();
    ForceSensorGlobal::IntervalTime = ui->sBox_Interval->value();

    emit sig_connectSerial();
    qDebug()<<"主线程 sig_connectSerial :"<<QThread::currentThreadId();

}

void MainWindow::on_pBtn_disconnectSerial_clicked()
{
    on_pBtn_stopRead_clicked();
    emit sig_disconnectSerial();
}

void MainWindow::on_connectSerialFinished(bool flag)
{
    if (flag)
    {
        // 设置控件可否使用
        ui->pBtn_connectSerial->setEnabled(false);
        ui->pBtn_refreshSerial->setEnabled(false);
        ui->pBtn_disconnectSerial->setEnabled(true);
    }
    else    //打开失败提示
    {

        QMessageBox::information(this,tr("错误"),tr("连接从站失败！"),QMessageBox::Ok);
    }
}

void MainWindow::on_disconnectSerialFinished(bool flag)
{
    if (flag)
    {
        // 设置控件可否使用
        ui->pBtn_connectSerial->setEnabled(true);
        ui->pBtn_refreshSerial->setEnabled(true);
        ui->pBtn_disconnectSerial->setEnabled(false);
    }
    else
    {
        QMessageBox::information(this,tr("错误"),tr("断开连接失败！"),QMessageBox::Ok);
    }

}

void MainWindow::on_pBtn_refreshSerial_clicked()
{
    //填充串口号组合框
    SearchSerialPorts();
}

void MainWindow::on_pBtn_startRead_clicked()
{
    ForceSensorGlobal::IntervalTime = ui->sBox_Interval->value();
    emit sig_startReadData();
    plotTimer->start();

}

void MainWindow::on_pBtn_stopRead_clicked()
{
    plotTimer->stop();
    emit sig_stopReadData();

}

}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114