title: Insert Byte inside QByteArray from QString - Qt C++
body: <p>I've little problem, I need to send trought modbus some bytes.
  One from some, is: 0x04, and 0xFB</p>
  
  <pre><code>QString first, second;
  first = "0x04";
  second = "0xFB"
  
  QByteArray array;
  array[0] = first;
  array[1] = second;
  ecc...ecc..
  </code></pre>
  
  <p>Ho to solve ? 
  I've tryed this: </p>
  
  <pre><code>array[0] = first.toUInt(nullptr,16);
  </code></pre>
  
  <p>but this last convert hex in other value.
  How to solve ? </p>