c++ - QSerial错误与Arduino通信

Question

我编写了一个简单的程序来使用 Qt(根据 this guide 之后的 Visual Studio 2013 源代码构建的 5.5 版)与 Arduino 进行通信。

这是一个简单的固件，它从串口读取并在 10 秒后打印“1”:

void setup() {
  Serial.begin(9600); //Open Serial connection for debugging
}

void loop() {
if (Serial.available()) {
    char user_input = Serial.read();
    if (user_input == '1') {
        delay(10000);
        Serial.print('1');
    }
}

这是 Qt 程序，当我按下开始按钮并继续监听要读取的消息时，它会在串行上发送“1”:

主要.cpp

#include "mainwindow.h"
#include <QApplication>

#pragma comment(lib, "advapi32")

int main(int argc, char *argv[]) {
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

主窗口.h

#pragma once

#include <QMainWindow>
#include "SerialHandler.h"

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow {
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow* ui;
    SerialHandler serialHandler;
public slots:
    void onStart();
};

主窗口.cpp

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

MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent), ui(new Ui::MainWindow), serialHandler(QString("COM6")) {
    ui->setupUi(this);
    QObject::connect(ui->startButton, SIGNAL(released()), this, SLOT(onStart()));
}

MainWindow::~MainWindow() {
    delete ui;
}

void MainWindow::onStart() {
    serialHandler.moveForward();
}

SerialHandler.h

#pragma once

#include <QString>
#include <QtSerialPort>
#include <QtSerialPort/QSerialPort>


class SerialHandler {
public:
    SerialHandler(QString& serialName);
    ~SerialHandler();
    void moveForward();

private:
    QSerialPort serial;
    void writeOnSerial(QByteArray& msg);

private slots:
    void handleReadyRead();
};

串口处理器.cpp

#include "SerialHandler.h"
#include <QDebug>
#include <QObject>


SerialHandler::SerialHandler(QString& serialName){
    connect(&serial, SIGNAL(readyRead()), this, SLOT(handleReadyRead()));

    // Initialize Serial
    serial.setPortName(serialName);

    if (!serial.setBaudRate(QSerialPort::Baud9600)) {
        throw std::runtime_error(QObject::tr("Can't set rate 9600 baud to port %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }

    if (!serial.open(QIODevice::ReadWrite)) {
        throw std::runtime_error(QObject::tr("Can't open %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }

    if (!serial.setDataBits(QSerialPort::Data8)) {
        throw std::runtime_error(QObject::tr("Can't set 8 data bits to port %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }

    if (!serial.setParity(QSerialPort::NoParity)) {
        throw std::runtime_error(QObject::tr("Can't set no patity to port %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }

    if (!serial.setStopBits(QSerialPort::OneStop)) {
        throw std::runtime_error(QObject::tr("Can't set 1 stop bit to port %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }

    if (!serial.setFlowControl(QSerialPort::NoFlowControl)) {
        throw std::runtime_error(QObject::tr("Can't set no flow control to port %1, error code %2")
            .arg(serial.portName()).arg(serial.error()).toStdString());
    }
}

SerialHandler::~SerialHandler(){
    if (serial.isOpen()) {
        serial.close();
    }
}

void SerialHandler::handleReadyRead() {
    qDebug() << serial.readAll();
}

void SerialHandler::writeOnSerial(QByteArray& msg) {
    if (serial.isOpen() && serial.isWritable()) {
        serial.write(msg);
        serial.flush();
    }
}

void SerialHandler::moveForward(){
    QByteArray msg("1");
    writeOnSerial(msg);
}

问题出现在 writeOnSerial 方法 (SerialHandler.cpp) 中。调用 serial.write() 会引发此错误:

QObject::startTimer: Timers can only be used with threads started with QThread

“1”写入串行并由 arduino 读取，但计算机在 10 秒后再也没有收到任何回复，readyRead() 信号永远不会被触发!

我在 this post 中看到了同样的错误，但在我的例子中，exec 循环就在那里!

有什么建议吗？

Answer 1

这个最小的测试用例适用于我在 Windows 和 OS X 上的 Arduino，使用最新的 Qt 5.5。

这种最小化属于你的问题。多个文件(以及缺少的 .ui)并不是演示此类简单故障所必需的。

// https://github.com/KubaO/stackoverflown/tree/master/questions/miniserial-36431493
#include <QtWidgets>
#include <QtSerialPort>

int main(int argc, char ** argv) {
   QApplication app(argc, argv);
   QWidget w;
   QFormLayout layout(&w);
   QPushButton ping("Send");
   QTextBrowser output;
   layout.addRow(&ping);
   layout.addRow(&output);
   w.show();

   QSerialPort port("COM6");
   port.setBaudRate(QSerialPort::Baud9600); // these are guaranteed to return true
   port.setDataBits(QSerialPort::Data8);
   port.setParity(QSerialPort::NoParity);
   port.setStopBits(QSerialPort::OneStop);
   port.setFlowControl(QSerialPort::NoFlowControl);
   if (!port.open(QIODevice::ReadWrite))
      output.append("! Can't open the port :(<br/>");

   QObject::connect(&ping, &QPushButton::clicked, &port, [&]{
      if (port.isOpen()) {
         port.write("1");
         output.append("> 1<br/>");
      } else
         output.append("! Write failed :(<br/>");
   });
   QObject::connect(&port, &QIODevice::readyRead, &output, [&]{
      auto data = port.readAll();
      output.append(QStringLiteral("< %1<br/>")
                    .arg(QString::fromLatin1(data).toHtmlEscaped()));
   });

   return app.exec();
}