我要用QT实现一个基本的Modbus RTU代码示例，并附上注释

以下是一个基本的Modbus RTU代码示例，使用QT编写，并加上注释：

#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>
#include <QDebug>

// Modbus RTU设备地址
const quint8 DEVICE_ADDRESS = 0x01;

// Modbus RTU功能码
const quint8 FUNCTION_READ_COILS = 0x01;
const quint8 FUNCTION_READ_HOLDING_REGISTERS = 0x03;

// Modbus RTU读取数据的起始地址和数量
const quint16 READ_START_ADDRESS = 0x0000;
const quint16 READ_DATA_COUNT = 0x0001;

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

// 打开串口
QSerialPort serialPort;
serialPort.setPortName("/dev/ttyUSB0");
serialPort.setBaudRate(QSerialPort::Baud9600);
serialPort.setDataBits(QSerialPort::Data8);
serialPort.setParity(QSerialPort::NoParity);
serialPort.setStopBits(QSerialPort::OneStop);
serialPort.setFlowControl(QSerialPort::NoFlowControl);
if (!serialPort.open(QIODevice::ReadWrite)) {
qDebug() << "Failed to open serial port";
return 1;
}

// 构造Modbus RTU读取数据的请求
QByteArray requestData;
QDataStream stream(&requestData, QIODevice::WriteOnly);
stream.setByteOrder(QDataStream::LittleEndian); // 数据流使用小端字节序
stream << quint8(DEVICE_ADDRESS) << quint8(FUNCTION_READ_COILS) << quint16(READ_START_ADDRESS) << quint16(READ_DATA_COUNT);

// 计算Modbus RTU读取数据的CRC校验码
quint16 crc = 0xFFFF;
for (int i = 0; i < requestData.size(); i++) {
quint8 byte = requestData.at(i);
crc ^= byte;
for (int j = 0; j < 8; j++) {
if (crc & 0x0001) {
crc >>= 1;
crc ^= 0xA001;
} else {
crc >>= 1;
}
}
}
requestData.append(crc & 0xFF);
requestData.append((crc >> 8) & 0xFF);

// 发送Modbus RTU读取数据的请求
serialPort.write(requestData);
if (!serialPort.waitForBytesWritten(1000)) {
qDebug() << "Failed to write data to serial port";
return 1;
}

// 等待Modbus RTU读取数据的响应
QByteArray responseData;
if (serialPort.waitForReadyRead(1000)) {
responseData = serialPort.readAll();
} else {
qDebug() << "Failed to read data from serial port";
return 1;
}

// 解析Modbus RTU读取数据的响应
QDataStream responseStream(responseData);
responseStream.setByteOrder(QDataStream::LittleEndian);
quint8 deviceAddress;
quint8 functionCode;
quint8 dataByteCount;
quint16 data;
quint16 crc16;
responseStream >> deviceAddress >> functionCode >> dataByteCount >> data >> crc16;
if (deviceAddress != DEVICE_ADDRESS || functionCode != FUNCTION_READ_HOLDING_REGISTERS || dataByteCount != 2) {
qDebug() << "Failed to parse response data";
return 1;
}

// 打印Modbus RTU读取的数据
qDebug() << "Read data:" << data;

// 关闭串口
serialPort.close();

return a.exec();
}