Qt下使用ModbusTcp通信协议进行PLC线圈/保持寄存器的读写（32位有符号数）

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系列文章目录

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第一章：Qt下使用ModbusTcp通信协议进行PLC线圈/保持寄存器的读写（32位有符号数）
第二章：Qt下使用modbus-c库实现PLC线圈/保持寄存器的读写

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文章目录

系列文章目录前言一、引入Modbus模块二、Modbus设备的连接三、各寄存器数据的读取四、各寄存器数据的写入五、示例完整代码总结

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前言

本文主要讲述了使用Qt的Modbus模块来进行ModbusTcp的通信，实现对PLC的线圈寄存器和保持寄存器的读写，基于TCP/IP的Modbus协议的内容我就不做过多解释了，详见参考文章。在本文示例中采用QModbusTcpClient类作为Modbus客户端（主站），PLC作为从站，封装了一个自己的MyModbus类，希望可以帮助到大家，如有错误之处，欢迎大家批评指正。

项目效果

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一、引入Modbus模块

1.这里我实现了自己的MyModbus类的封装，使用了pri子模块的方式，也是方便日后进行此模块的复用
pri中引入Modbus模块：
MyModbus.pri

QT   += serialbus serialport

MyModbus类中添加相关头文件

#include <QModbusTcpClient>#include <QModbusDataUnit>

二、Modbus设备的连接

1.ModbusTcp的连接只需要配置好连接参数IP+Port

//判断当前连接状态是否为断开状态if(myClient->state() != QModbusDevice::ConnectedState){    //配置ModbusTcp的连接参数IP+Port    myClient->setConnectionParameter(QModbusDevice::NetworkAddressParameter,ip);    myClient->setConnectionParameter(QModbusDevice::NetworkPortParameter,port);    myClient->connectDevice();}

三、各寄存器数据的读取

1.Modbus中有4种操作对象，这4种都能进行读取操作：线圈、离散输入、保持寄存器、输入寄存器

//读取modbus设备各寄存器数据//typeNum:1_线圈 2_离散输入 3_保持 4_输入bool MyModbus::readModbusData(int typeNum,int startAdd,quint16 numbers){    if(myClient->state() != QModbusDevice::ConnectedState)    {        return false;    }    //确定寄存器类型    QModbusDataUnit ReadUnit;    if(typeNum == 1)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::Coils,startAdd,numbers);    }    else if(typeNum == 2)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::DiscreteInputs,startAdd,numbers);    }    else if(typeNum == 3)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters,startAdd,numbers);    }    else if(typeNum == 4)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::InputRegisters,startAdd,numbers);    }    else    {        LOGDEBUG<<"读取寄存器类型错误";        return false;    }    LOGDEBUG<<"readModbusData typeNum:"<<typeNum;    //多读    if(auto *reply = myClient->sendReadRequest(ReadUnit,1))    {        if(!reply->isFinished())        {            if((typeNum == 1) || (typeNum == 2))            {                QObject::connect(reply,&QModbusReply::finished,this,&MyModbus::slot_readReadyCoils);   //读取线圈            }            if((typeNum == 3) || (typeNum == 4))            {                QObject::connect(reply,&QModbusReply::finished,this,&MyModbus::slot_readReadyRegisters);   //读取寄存器            }            //reply->deleteLater();            return true;        }        else        {            reply->deleteLater();            return false;        }    }    else    {        LOGDEBUG<<"读取错误:" + myClient->errorString();        return false;    }}

四、各寄存器数据的写入

1.Modbus中4种操作对象只有这2种能进行写入操作：线圈 、保持寄存器

//对modbus设备各寄存器写入数据//typeNum:1_线圈 2_保持 (这两类寄存器可读可写,其余的只读)bool MyModbus::writeModbusData(int typeNum,int startAdd,int writeNum){    if(myClient->state() != QModbusDevice::ConnectedState)    {        return false;    }    //确定寄存器类型    QModbusDataUnit writeUnit;    if(typeNum == 1)    {        writeUnit = QModbusDataUnit(QModbusDataUnit::Coils,startAdd,1);   //写入一个数据        writeUnit.setValue(0,writeNum);        //单写        //bool ok;        //quint16 hexData = writeData.toInt(&ok,16);   //转16进制    }    else if(typeNum == 2)    {        writeUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters,startAdd,2);   //写入两个数据        quint16 uData16[2] = {0};        uData16[0] = writeNum & 0xffff;        uData16[1] = (writeNum >> 16) & 0xffff;        writeUnit.setValue(0,uData16[0]);        writeUnit.setValue(1,uData16[1]);        //LOGDEBUG<<"uData16[0]:"<<uData16[0]<<"   uData16[1]:"<<uData16[1]<<"   writeNum:"<<writeNum;    }    else    {        LOGDEBUG<<"写入寄存器类型错误";        return false;    }    //LOGDEBUG<<"writeModbusData typeNum:"<<typeNum<<"   writeNum:"<<writeNum;    if(auto *reply = myClient->sendWriteRequest(writeUnit,1))    {        if(!reply->isFinished())        {            connect(reply,&QModbusReply::finished,this,[reply]()            {                if(reply->error() == QModbusDevice::NoError)                {                    reply->deleteLater();                    return true;                }                else                {                    LOGDEBUG<<"写入返回错误:"<<reply->error();                    reply->deleteLater();                    return false;                }            });        }        else        {            reply->deleteLater();            return false;        }    }    else    {        LOGDEBUG<<"写入错误:" + myClient->errorString();        return false;    }    return true;}

五、示例完整代码

这里是示例项目的完整代码，包含pro主程序和MyModbus.pri子文件
1.ModbusTest.pro

QT   += core guigreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsCONFIG += c++11#定义编译选项.QT_DEPRECATED_WARNINGS表示当Qt的某些功能被标记为过时的,那么编译器会发出警告.DEFINES += QT_DEPRECATED_WARNINGS#设置字符(MSCV编译器下防止中文乱码)contains( CONFIG,"msvc" ):QMAKE_CXXFLAGS += /source-charset:utf-8 /execution-charset:utf-8contains( CONFIG,"msvc" ):QMAKE_CFLAGS +=/source-charset:utf-8 /execution-charset:utf-8include (./MyModbus/MyModbus.pri)SOURCES += \    main.cpp \    widget.cppHEADERS += \    widget.hFORMS += \    widget.ui# Default rules for deployment.qnx: target.path = /tmp/$${TARGET}/binelse: unix:!android: target.path = /opt/$${TARGET}/bin!isEmpty(target.path): INSTALLS += target

2.MyModbus.pri

QT       += serialbus serialportHEADERS += \    $$PWD/mymodbus.hSOURCES += \    $$PWD/mymodbus.cpp

3.mymodbus.h

#ifndef MYMODBUS_H#define MYMODBUS_H#include <QObject>#include <QModbusTcpClient>#include <QModbusDataUnit>#include <QDebug>#define LOGDEBUG qDebug()<<__FILE__<<__LINE__class MyModbus : public QObject{    Q_OBJECTpublic:    explicit MyModbus(QObject *parent = nullptr);    ~MyModbus();    void initModbus();    void connectToModbus(QString ip,int port);    bool readModbusData(int typeNum,int startAdd,quint16 numbers);    bool writeModbusData(int typeNum,int startAdd,int writeNum);signals:    void signal_stateChanged(bool flag);    void signal_readCoils(QVector<quint16> vAllData);    void signal_readRegisters(int resultNum);private slots:    void slot_stateChanged();    void slot_readReadyCoils();    void slot_readReadyRegisters();private:    QModbusTcpClient *myClient;};#endif // MYMODBUS_H

4.mymodbus.cpp

#include "mymodbus.h"MyModbus::MyModbus(QObject *parent) : QObject(parent){    this->initModbus();}MyModbus::~MyModbus(){}//初始化void MyModbus::initModbus(){    myClient = new QModbusTcpClient();    //connect(myClient,SIGNAL(stateChanged()),this,SLOT(slot_stateChanged()));    connect(myClient,&QModbusClient::stateChanged,this,&MyModbus::slot_stateChanged);}//连接到modbus设备void MyModbus::connectToModbus(QString ip,int port){    if(!myClient)    {        return;    }    //判断当前连接状态是否为断开状态    if(myClient->state() != QModbusDevice::ConnectedState)    {        //配置ModbusTcp的连接参数IP+Port        myClient->setConnectionParameter(QModbusDevice::NetworkAddressParameter,ip);        myClient->setConnectionParameter(QModbusDevice::NetworkPortParameter,port);        myClient->connectDevice();    }    //else    //{    //    myClient->disconnectDevice();    //}}//读取modbus设备各寄存器数据//typeNum:1_线圈 2_离散输入 3_保持 4_输入bool MyModbus::readModbusData(int typeNum,int startAdd,quint16 numbers){    if(myClient->state() != QModbusDevice::ConnectedState)    {        return false;    }    //确定寄存器类型    QModbusDataUnit ReadUnit;    if(typeNum == 1)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::Coils,startAdd,numbers);    }    else if(typeNum == 2)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::DiscreteInputs,startAdd,numbers);    }    else if(typeNum == 3)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters,startAdd,numbers);    }    else if(typeNum == 4)    {        ReadUnit = QModbusDataUnit(QModbusDataUnit::InputRegisters,startAdd,numbers);    }    else    {        LOGDEBUG<<"读取寄存器类型错误";        return false;    }    LOGDEBUG<<"readModbusData typeNum:"<<typeNum;    //多读    if(auto *reply = myClient->sendReadRequest(ReadUnit,1))    {        if(!reply->isFinished())        {            if((typeNum == 1) || (typeNum == 2))            {                QObject::connect(reply,&QModbusReply::finished,this,&MyModbus::slot_readReadyCoils);   //读取线圈            }            if((typeNum == 3) || (typeNum == 4))            {                QObject::connect(reply,&QModbusReply::finished,this,&MyModbus::slot_readReadyRegisters);   //读取寄存器            }            //reply->deleteLater();            return true;        }        else        {            reply->deleteLater();            return false;        }    }    else    {        LOGDEBUG<<"读取错误:" + myClient->errorString();        return false;    }}//对modbus设备各寄存器写入数据//typeNum:1_线圈 2_保持 (这两类寄存器可读可写,其余的只读)bool MyModbus::writeModbusData(int typeNum,int startAdd,int writeNum){    if(myClient->state() != QModbusDevice::ConnectedState)    {        return false;    }    //确定寄存器类型    QModbusDataUnit writeUnit;    if(typeNum == 1)    {        writeUnit = QModbusDataUnit(QModbusDataUnit::Coils,startAdd,1);   //写入一个数据        writeUnit.setValue(0,writeNum);        //单写        //bool ok;        //quint16 hexData = writeData.toInt(&ok,16);   //转16进制    }    else if(typeNum == 2)    {        writeUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters,startAdd,2);   //写入两个数据        quint16 uData16[2] = {0};        uData16[0] = writeNum & 0xffff;        uData16[1] = (writeNum >> 16) & 0xffff;        writeUnit.setValue(0,uData16[0]);        writeUnit.setValue(1,uData16[1]);        //LOGDEBUG<<"uData16[0]:"<<uData16[0]<<"   uData16[1]:"<<uData16[1]<<"   writeNum:"<<writeNum;    }    else    {        LOGDEBUG<<"写入寄存器类型错误";        return false;    }    //LOGDEBUG<<"writeModbusData typeNum:"<<typeNum<<"   writeNum:"<<writeNum;    if(auto *reply = myClient->sendWriteRequest(writeUnit,1))    {        if(!reply->isFinished())        {            connect(reply,&QModbusReply::finished,this,[reply]()            {                if(reply->error() == QModbusDevice::NoError)                {                    reply->deleteLater();                    return true;                }                else                {                    LOGDEBUG<<"写入返回错误:"<<reply->error();                    reply->deleteLater();                    return false;                }            });        }        else        {            reply->deleteLater();            return false;        }    }    else    {        LOGDEBUG<<"写入错误:" + myClient->errorString();        return false;    }    return true;}//监听TCP连接的状态,若状态发生改变,发出对应的信号void MyModbus::slot_stateChanged(){    LOGDEBUG<<myClient->state();    if(myClient->state() == QModbusDevice::ConnectedState)    {        emit signal_stateChanged(true);    }    else if(myClient->state() == QModbusDevice::UnconnectedState)    {        emit signal_stateChanged(false);    }}//接收到读取线圈/离散输入寄存器请求后执行的槽函数void MyModbus::slot_readReadyCoils(){    QVector<quint16> vAllData;    QModbusReply *reply = qobject_cast<QModbusReply *>(sender());    if(!reply)    {        LOGDEBUG<<"读取线圈/离散输入寄存器错误";        return;    }    if(reply->error() == QModbusDevice::NoError)    {        const QModbusDataUnit unit = reply->result();        vAllData = unit.values();        emit signal_readCoils(vAllData);    }    else    {        LOGDEBUG<<"线圈/离散输入寄存器回复错误:"<<reply->error();    }    reply->deleteLater();}//接收到读取保持/输入寄存器请求后执行的槽函数void MyModbus::slot_readReadyRegisters(){    QModbusReply *reply = qobject_cast<QModbusReply *>(sender());    if(!reply)    {        LOGDEBUG<<"读取保持/输入寄存器错误";        return;    }    if(reply->error() == QModbusDevice::NoError)    {        const QModbusDataUnit unit = reply->result();        auto valueList = unit.values();        int nSize = valueList.size();        if(nSize == 2)        {            quint16 uData16[2] = {0};            uData16[0] = valueList[0];            uData16[1] = valueList[1];            int resultNum = uData16[0] | (uData16[1] << 16);            //LOGDEBUG<<"uData16[0]:"<<uData16[0]<<"   uData16[1]:"<<uData16[1]<<"   resultNum:"<<resultNum;            emit signal_readRegisters(resultNum);        }        else        {            LOGDEBUG<<"保持寄存器返回数据错误,个数:"<<nSize;        }    }    else    {        LOGDEBUG<<"保持/输入寄存器回复错误:"<<reply->error();    }    reply->deleteLater();}/*//读取保持/输入寄存器数据的另一种方式,已废弃//当前数据格式为大端模式,高位存低地址//判断正负数,以高8位的16进制是否为f判断int resultNum = 0;if(QString::number(valueList[1],16).left(1) == "f")   //负数{    //判断是否小于-65535,高16位的10进制为65535    if(valueList[1] == 65535)    {        resultNum = valueList[0] - 65536;    }    else    {        resultNum = (valueList[1] - 65535) * 65536 + (valueList[0] - 65536);    }}else{    //判断是否大于65535,高16位的10进制大于0    if(valueList[1] > 0)    {        resultNum = valueList[1] * 65536 + valueList[0];    }    else    {        resultNum = valueList[0];    }}*/

5.widget.h

#ifndef WIDGET_H#define WIDGET_H#include <QWidget>#include <QFileDialog>#include <QDateTime>#include <QMessageBox>#include "MyModbus/mymodbus.h"QT_BEGIN_NAMESPACEnamespace Ui { class Widget; }QT_END_NAMESPACEclass Widget : public QWidget{    Q_OBJECTpublic:    Widget(QWidget *parent = nullptr);    ~Widget();    void initWidget();private slots:    void slot_stateChanged(bool flag);    void slot_readCoils(QVector<quint16> vAllData);    void slot_readRegisters(int resultNum);private slots:    void on_pb_connect_clicked();    void on_pb_readM_clicked();    void on_pb_writeM_clicked();    void on_pb_readD_clicked();    void on_pb_writeD_clicked();private:    Ui::Widget *ui;    MyModbus *m_myModsbus;   //MyModbus对象};#endif // WIDGET_H

6.widget.cpp

#include "widget.h"#include "ui_widget.h"Widget::Widget(QWidget *parent)    : QWidget(parent)    , ui(new Ui::Widget){    ui->setupUi(this);    this->initWidget();}Widget::~Widget(){    delete ui;}void Widget::initWidget(){    //初始化MyModbus对象    m_myModsbus = new MyModbus();    connect(m_myModsbus,SIGNAL(signal_stateChanged(bool)),this,SLOT(slot_stateChanged(bool)));    connect(m_myModsbus,SIGNAL(signal_readCoils(QVector<quint16>)),this,SLOT(slot_readCoils(QVector<quint16>)));    connect(m_myModsbus,SIGNAL(signal_readRegisters(int)),this,SLOT(slot_readRegisters(int)));}void Widget::slot_stateChanged(bool flag){    if(flag)    {        ui->lb_state->setText("连接成功");        ui->te_show->appendPlainText(QTime::currentTime().toString("hh:mm:ss: ") + "连接成功");        QMessageBox::warning(this,"警告","连接成功!");    }    else    {        ui->lb_state->setText("连接断开");        ui->te_show->appendPlainText(QTime::currentTime().toString("hh:mm:ss: ") + "连接断开");        QMessageBox::warning(this,"警告","连接断开!");    }}void Widget::slot_readCoils(QVector<quint16> vAllData){    LOGDEBUG<<"readCoils size:"<<vAllData.size();    for(int i=0;i<vAllData.size();i++)    {        LOGDEBUG<<"i:"<<vAllData[i];        ui->te_show->appendPlainText(QTime::currentTime().toString("hh:mm:ss: ") + "读取M区返回数据:" + QString::number(vAllData[i]));        ui->le_dataM->setText(QString::number(vAllData[0]));    }}void Widget::slot_readRegisters(int resultNum){    LOGDEBUG<<"resultNum:"<<resultNum;    ui->te_show->appendPlainText(QTime::currentTime().toString("hh:mm:ss: ") + "读取D区返回数据:" + QString::number(resultNum));    ui->le_dataD->setText(QString::number(resultNum));}void Widget::on_pb_connect_clicked(){    QString ip = ui->le_ip->text();    int port = ui->le_port->text().toInt();    LOGDEBUG<<"ip:"<<ip<<"   port:"<<port;    ui->te_show->appendPlainText(QTime::currentTime().toString("hh:mm:ss: ") + "ip:" + ip + " port:" + QString::number(port));    //连接到modbus设备    m_myModsbus->connectToModbus(ip,port);}void Widget::on_pb_readM_clicked(){    int startAdd = ui->le_addressM->text().toInt();    LOGDEBUG<<"startAdd:"<<startAdd;    if(!m_myModsbus->readModbusData(1,startAdd,1))    {        QMessageBox::warning(this,"警告","M区数据读取失败!");    }}void Widget::on_pb_writeM_clicked(){    int startAdd = ui->le_addressM->text().toInt();    int writeNum = ui->le_dataM->text().toInt();    LOGDEBUG<<"startAdd:"<<startAdd<<"   writeNum:"<<writeNum;    //单写    if(!m_myModsbus->writeModbusData(1,startAdd,writeNum))    {        QMessageBox::warning(this,"警告","M区数据写入失败!");    }}void Widget::on_pb_readD_clicked(){    int startAdd = ui->le_addressD->text().toInt();    LOGDEBUG<<"startAdd:"<<startAdd;    if(!m_myModsbus->readModbusData(3,startAdd,2))    {        QMessageBox::warning(this,"警告","D区数据读取失败!");    }}void Widget::on_pb_writeD_clicked(){    int startAdd = ui->le_addressD->text().toInt();    int writeNum = ui->le_dataD->text().toInt();;    LOGDEBUG<<"startAdd:"<<startAdd<<"   writeNum:"<<writeNum;    //进行写入寄存器数据的处理    if(!m_myModsbus->writeModbusData(2,startAdd,writeNum))    {        QMessageBox::warning(this,"警告","D区数据写入失败!");    }}

7.main.cpp

#include "widget.h"#include <QApplication>#include <QMutex>//程序输出日志void outputMessage(QtMsgType type,const QMessageLogContext &context,const QString &msg){    static QMutex mutex;    mutex.lock();    //初始化log文件夹    QString logFilePath = QCoreApplication::applicationDirPath() + "/LogFile/";    QDir dstDir(logFilePath);    if(!dstDir.exists())    {        if(!dstDir.mkpath(logFilePath))        {            LOGDEBUG<<"程序输出日志创建失败！";        }        else        {            LOGDEBUG<<"程序输出日志创建成功！";        }    }    //获取输出内容    QString debugMsg;    if(type == QtDebugMsg)    {        QString debugDateTime = QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss");        debugMsg = QString("%1\n%2%3").arg(debugDateTime).arg(msg).arg(context.function);    }    //保存文件    QString curDate = QDate::currentDate().toString("yyyyMMdd");    QString logFile = logFilePath + "log_" + curDate + ".txt";    QFile file(logFile);    file.open(QIODevice::WriteOnly | QIODevice::Append);    QTextStream textStream(&file);    textStream << debugMsg << "\n\n";    file.flush();    file.close();    mutex.unlock();}int main(int argc, char *argv[]){    QApplication a(argc, argv);    qInstallMessageHandler(outputMessage);    Widget w;    w.show();    return a.exec();}

8.widget.ui

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总结

基于Qt使用这个ModbusTcp协议进行通信，还是比较简单的，首先就是确定下寄存器的类型，直接使用相关的函数进行读写。需要注意的一点是在进行保持寄存器读写的时候，我们PLC某个地址上的数是个16位的数，所以在进行32位有符号数读写的时候，要考虑两个相邻地址的组合，文中就对此进行了处理，这种情况下PLC那边也别忘记进行相应的设置哈。

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hello：
共同学习，共同进步，如果还有相关问题，可在评论区留言进行讨论。

参考博客：
QT下的Modbus TCP 通讯
C++与PLC通过Modbus TCP协议进行PLC内部寄存器的值的读取/写入总结

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