[Solved] QTSerialPort QByteArray Receive values higher than 127

[paulogp]

I have a device that outputs 3 signals (values: temperature, speed, frequency) via rs232. The code that I use to capture the signals is the following:
@if (serial->bytesAvailable() == 3)
{
QByteArray buffer;
buffer = serial->readAll();
qDebug() << (int)buffer[0] << ":" << (int)buffer[1] << ":" << (int)buffer[2];
}@

Example of an output: 65 : 10 : 98.

The problem is that the values can go much higher than 127 that produces an output of negative values (-1, -60, ..). In Java we can use readIntArray; does anyone knows a way to read the values using QTSerialPort? Thanks in advance!

[mrdebug]

You can obtain a QString from QByteArray and then split on ":".
After that the first element will be temp, the second speed and other.
It' easy.

[paulogp]

Thanks for the reply. The ":" are inserted in the qDebug(), unfortunately that doesn't do part of the signal.

[mrdebug]

Can you post the exactly byte sequence, with first, last and control byte?

[qxoz]

Try change it to:
@qDebug() << quint8(buffer[0]) << ":" << quint8(buffer[1]) << ":" << quint8(buffer[2]);@

[paulogp]

Reading the device manual, what I only know is that it sends 3 sequencial "signals" (that corresponds to temperature, speed, frequency) from time to time.

For example; I receive the 3 sequencial numbers:
65 (temperature)
10 (speed)
98 (frequency)

10 minutes later:
256
3
128

23 minutes later:
250
100
192

and so on...

Init:
@serial->setBaudRate(QSerialPort::Baud1200);
serial->setDataBits(QSerialPort::Data8);
serial->setParity(QSerialPort::NoParity);
serial->setStopBits(QSerialPort::OneStop);
serial->setFlowControl(QSerialPort::NoFlowControl);@

@if (serial->bytesAvailable() == 3)
{
QByteArray buffer;
buffer = serial->readAll();
qDebug() << (int)buffer[0] << ":" << (int)buffer[1] << ":" << (int)buffer[2];
}@

I have no problem "catching" the values, my problems is with value itself. When (int)buffer[ 0 ] or (int)buffer[ 1 ] or (int)buffer[ 2 ] is higher than 127 it shows negative numbers (68, 5, -1) because byte goes from -127 to 127.

[paulogp]

Thanks, I will give it a try qxoz.

[Jeroentjehome]

Hi, do you need to add up two bytes into a signed int??
Maybe something like this:
int MyInt ((qint16)buffer[0] << 8 + (qint16)buffer[1]);
or if that failed, you could do something like this:
@
QByteArray MyInt (buffer.chop(2));
qDebug() << MyInt.toInt();
@

[paulogp]

Thanks all for the replies. The solution presented by qxoz worked like a charm.

@ if (serial->bytesAvailable() == 3)
{
QByteArray buffer;
buffer = serial->readAll();
qDebug() << (quint8)buffer[0] << ":" << (quint8)buffer[1] << ":" << (quint8)buffer[2];
}
@

[miguelangellv]

Other solution is use QDataStream

@ if (serial->bytesAvailable() == 3)
{
QDataStream buffer(serial->readAll(), QIODevice::ReadOnly);
quint8 data1;
quint8 data2;
quint8 data3;

    buffer >> data1;
    buffer >> data2;
    buffer >> data3;
}@