[solved] incomplete data read by qserialdevice

vezprog

Use QExtSerialPort, download it and just build the library and link it to your application

Heres how I read the serial port instead of events (which can get hairy when parsing a lot of data)

Start a while loop
Set and start a timer for X milliseconds so when it fires, it changes the state of the while loop variable so you can exit the while loop
Check for data on the port by using bytesavailable()
Sit in while loop for a little while and keep reading the port until no more data is available or until a delimiter is reached
use QCoreApplication::processEvents() while in the while loop so the gui doesn't freeze up

Boom, timer fires, you delayed X mS to get all the data from where ever

Carry on with what you want to do.

arianoo

What u say about events making problem is quite correct ive even seen some cases in my own application but the method you are talking about makes lots of time loss which is very important in my case and i cant ignore it. i should write the program in a way that it works as fast as possible and i guess that i can achieve it via signals and events but maybe i'm wrong and using a while loop when needed to read data till its complete is better? Im getting curious about which way will make the program work faster???????

vezprog

I guess it depends, do you know the size of the data that your expecting? Is there a delimiter on your string that you are expecting through the serial? You could do some simple timing tests to optimize your program.

Either that, or when you get an event that data is on your port, then sit in a while and read, and repeat my previous suggestion.

kuzulis

We strongly recommend using QSerialDevice 2.0.

People, you have ever read that thread "link":http://developer.qt.nokia.com/forums/viewthread/11634/#67246, which showed by Mr. koahnig?

I recommend to read.

arianoo

yea I'm using QSerialDevice and i hope to get better in working with this class because 90% of my application is about working with serial ports and its so important for me. dvez yes i can find the size of coming data by its third byte coming (if i get the first third bytes exactly as theyre sent) and i can stay in the while loop till i get as much data as i need and i can also call it when i send something and im waiting to get answer.do u think it'll work faster and ill be able to read data without getting it damaged?

koahnig

[quote author="arianoo" date="1323964918"]yea I'm using QSerialDevice and i hope to get better in working with this class because 90% of my application is about working with serial ports and its so important for me. dvez yes i can find the size of coming data by its third byte coming (if i get the first third bytes exactly as theyre sent) and i can stay in the while loop till i get as much data as i need and i can also call it when i send something and im waiting to get answer.do u think it'll work faster and ill be able to read data without getting it damaged? [/quote]

Did you update to QSerialdevice 2.0 ?

arianoo

wow thanks alot for mentioning it i thought that im using the latest version but i wasnt! i did it recently and havent faced anything different up to now just a question why do u think the "setcharintervaltimeout" slot which was i think effective on reading data omitted in this version do u believe that it wont get me into any trouble?

abhijsj

I had updated to qserialdevice 2.0 and i am able to open multiple ports through this library.
While reading data i faced a problem that if i am sending 10 bytes of data it is read as 8 bytes,2 bytes. Data is always received in fragments of 8 bytes only. I have checked all the examples of qserialdevice 2.0 all of them have the same problem. I dont know how to overcome this problem .

Someone please guide me.

Thanks in Advance

kuzulis

Abhishek,
Do not torture the brain, I have already explained to you by e-mail the cause, and that in this situation needs to be done, what approaches to use.

Final decision of your problems, no one will give you.

[quote]
While reading data i faced a problem that if i am sending 10 bytes of data it is read as 8 bytes,2 bytes.
[/quote]
This is not a problem. This is normal behavior for non-blocking data is received.

Is it hard to think of, like this to such a:
[code]
class Reader : public QObject
{
Q_OBJECT
signals:
void onePacketReceivedComplete(const QByteArary &packet);

public:

enum { 
    ExpectedResponseSize = 78 // Your expected size of the incoming packet
}; 

Reader() {
    m_port = new SerialPort(this);
    connect(m_port, SIGNAL(readyRead(), this, SLOT(checkAvailable()));
    ...
    // Open and configure port
    ...
    
    m_timer = new QTimer(this);
    connect(m_timer, SIGNAL(timeout()), this, SLOT(processRead()));
    m_timer->setInterval(10); // Maximum interval a wait end of packet, 10 msec (for example)
    ...
}

private slots:

void checkAvailable() {
    if (m_port->bytesAvailable() < ExpectedResponseSize) {
       if (!m_timer->isActive())
            m_timer->start();
    } else {
        processRead();       
    }

void processRead() {
    m_timer->stop();
    
    // Here search a marker/header field in beginning of the packet 
    // (use peek(), example) or etc,
    // ie, is synchronized with the input packets 
    // (looking for begin a valid package from stream).
    ...
    ...
    
    QByteArray incomingData = m_port->read(ExpectedResponseSize);

    // Here check CRC and etc
    ...
    ...

    // If all checks are successful - it returns the packet.
    if (isOk) { 
        emit onePacketReceivedComplete(incomingData);
    } else {
        // do
    }
}

private:
SerialPort *m_port;
QTimer *m_timer;
};
[/code]

???

hendri

thank kuzulis, i am getting stuck with this problem (incomplete data read) and i found the solution only in this site. thanks again