I want to do some casting from signed char to unsigned char using

QByteArray block;
block = tcpSocket->readAll();

Qt Code:
  1. unsigned char* ublock = static_cast<unsigned char*>(block.data());
To copy to clipboard, switch view to plain text mode 

but get
error: invalid static_cast from type `char*' to type `unsigned char*'
Can someone explain where I am going wrong?