QSerialPort - transmition errors

[michelson]

Hello guys,
i have some problems in reading bytes using QSerialPort. I implemented readyRead() - readAll() signal-slot system but it seems to be working incorectly. I have to read about 3Mb of data (continuous transmition) but the bytes read by readAll() function are all zeros. I tested the device using some terminal application and it seems to work fine. Does anyone experienced similar problem in their work?

simplified code here:

char datawrite[] = {0x01,0x02}; // device commands which i should get response from
QByteArray dataread;
serial->write(datawrite);
 ...
// handle readyRead()
 void on_readyRead() {
       dataread.append(serial->readAll());
}

[edit: fixed coding tags ``` SGaist]

[SGaist]

Hi,

Please post the un-simplified code. From what you posted you might be using two different QByteArrays with the same name so one would stay empty and not the other one.

[michelson]

HEADER:

#ifndef SESIONPROGRAMING_H
#define SESIONPROGRAMING_H

#include <QMainWindow>
#include <QSerialPort>

namespace Ui {
class SesionPrograming;
}

class SesionPrograming : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void handleError(QSerialPort::SerialPortError error);
    void openSerialPort();
    void closeSerialPort();
    void writeData(const QByteArray &data);
    void readData();

private:
    QByteArray reciveddata;
    int readcalls;
    char charbuff[1];
    Ui::SesionPrograming *ui;
    QSerialPort *serial;

};

#endif // SESIONPROGRAMING_H

SOURCE:

#include <QMessageBox>
#include <QDebug>
#include <windows.h>

SesionPrograming::SesionPrograming(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::SesionPrograming)
{
    ui->setupUi(this);
    serial = new QSerialPort(this);
    serial->setBaudRate(QSerialPort::Baud115200);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->setPortName("COM5");
    connect(serial, SIGNAL(readyRead()), this, SLOT(readData()));
    connect(serial, SIGNAL(error(QSerialPort::SerialPortError)), this,
            SLOT(handleError(QSerialPort::SerialPortError)));
    openSerialPort();
    const char commands[] = {0xb0};
    QByteArray writeba(commands);
    writeData(writeba);
}

SesionPrograming::~SesionPrograming()
{
    qDebug() << reciveddata.toHex();
    qDebug() << reciveddata;
    qDebug() << reciveddata.size();
    qDebug() << readcalls;
    closeSerialPort();
    delete ui;
}

void SesionPrograming::handleError(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError) {
        QMessageBox::critical(this, tr("Critical Error"), serial->errorString());
        closeSerialPort();
    }
}

void SesionPrograming::writeData(const QByteArray &data)
{
    serial->write(data);
}

void SesionPrograming::readData()
{
    reciveddata.append(serial->readAll());
}
void SesionPrograming::openSerialPort()
{
    if (serial->open(QIODevice::ReadWrite))
    {
        qDebug()<<"połączono z portem com4";
    }
    else
    {
        QMessageBox::critical(this, tr("Error"), serial->errorString());
    }
}

void SesionPrograming::closeSerialPort()
{
    if (serial->isOpen())
        serial->close();
}

[SGaist]

Why are you calling serial->clear()?

Please enclose your code with coding tags: three back-ticks before and after.

[michelson]

Im sorry, i was messing around with code to work something out, thought there might be some rubbish in the buffer so i thought clearing it may fix the problem (in fact it doesnt)

[michelson]

Another strange behaviour here:
The device has a list of commands i.e
0x02 - return name (8bytes)
0x04 - return firmware (12bytes)
When i write above commands it responds correctly but when i use this 0x80... command which should get me the measurment data (thousands of bytes) it sends only zeros (again, i tested the device in external terminal app and it worked fine...) so in my opinion the length of data is the problem. But why?

[kuzulis]

Why you are think that it is correct?

    const char commands[] = {0xb0};
    QByteArray writeba(commands);

QByteArray is not the telepathist, so try this instead:

    const char commands[] = {0xb0};
    QByteArray writeba(commands, sizeof(commands));

and check that QByteArray contains desired bytes.