CODEWITHSUNDEEP
c++qtqmap
voidpointer
voidpointer

Reputation: 301

QMap<int,QByteArray> return Wrong QByteArray

I am using 

QMap < int, QByteArray> RegTable; (Seprate Class Variable)

to storing Modbus Register Address and data received from Serial Port. Everything working fine, data read from the serial port and fill to the QByteArray correctly.

qDebug() << Modbus->RegTable[RegAddr].toHex(' ');

print the correct data. But if want to write variable using it then always the same value/Garbage stored in this variable.

    unsigned int unixTimeStamp = 0;
    qDebug() << Modbus->RegTable[RegAddr].toHex(' ');

    unixTimeStamp  = static_cast <unsigned int>Modbus->RegTable[RegAddr].at(4);
    unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(5)<<8;
    unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(6)<<16;
    unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(7)<<24;

    QDateTime timestamp;
    timestamp.setTime_t(unixTimeStamp  );
    qDebug() << timestamp.toString(Qt::SystemLocaleShortDate); //wrong time

RegTable is Modbus Class variable, And I used it to the main class but always I get the wrong data or values.

Upvotes: 1

Views: 317

Answers (1)

Some programmer dude
Some programmer dude

Reputation: 409442

With

unixTimeStamp |= ...;

you write to the same byte over and over again. You need to shift the values:

unixTimeStamp  = static_cast <unsigned int>Modbus->RegTable[RegAddr].at(4) << 24;
unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(5) << 16;
unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(6) <<  8;
unixTimeStamp |= static_cast <unsigned int>Modbus->RegTable[RegAddr].at(7);

Of course, the shifts might have to be done in the opposite order depending on byte order.

Upvotes: 1

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