Qt4.8 on VxWorks// Converting QString to unsigned char

  • I am a newbie to Qt and programming in general and have a question to ask.

    I need to execute commands to set display contrast and it has data format as below:

    [command][data][Checksum =command +data]

    Contrast 100 -> Command : [0x83][0x64][0xE7]

    Brief explanation: I need to implement something that reads int type of contrast value and convert it to hex value and execute as above command. I converted the int value to QString type of hex value but do not know how to convert QString to char type.

    I tried below, but it only prints the fist value. For instance if checksum is E7, it only prints E.
    is there a way to convert to char and store E7 instead of just first E?

    @char checkSum1=QString(Sum).at(0).toLatin1(); // only prints the first value.@

    Below are Data structure and what I have tried.

    union serialData
    unsigned char bytes[SERIAL_DATA_LENGTH];
    struct {
    unsigned char command;
    unsigned char data;
    unsigned char checkSum;

    } format;


    void SettingButton::formatSettingValue(AppConstants::SettingType type)
    QString hexVal,Sum;

    int value=ui->ValueProgressBar->value();
    hexVal= QString("0x%1").arg(hexVal);
    int sum= value+131; // 0x83 is 131 in Decimal
    Sum= QString("0x%1").arg(Sum);
    char checkSum1=QString(Sum).at(0).toLatin1(); // only prints the first value.
    char checkSum2=QString(Sum).at(1).toLatin1();// prints the second value
    switch (type)
    case AppConstants::BRIGHTNESS:
    case AppConstants::CONTRAST:


    Thanks in advance.

  • Hi,

    QByteArray hex = QByteArray::number(value, 16)

    Here hex will be of size() == 2, where hex.at(0) and hex.at(1) are chars.

    See the "function documentation":http://doc.qt.io/qt-5/qbytearray.html#number for more details.

    A general note: Qt has en exceptionally good documentation where you can find example code where you need it. Always first check the docs and you may solve your issues much faster.

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