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.