don't receive data with lib

[ffbboy30]

Hi,
I've tried the Extra sample with my Due , I received the ubx packet starting with 0xB5 and 0x62.
When I try to implement the lib with the same config , nothing append.
I try to add a serial print in the ubxgps.h to debug the UART reception

  boolean ready()
  {
      byte c = this->read();
      serial.print(c,HEX);    
    return true;
}

but nothing print like if the port is not opened .
Do you have a tips ?
Thanks