UART Arduino Due SAM3X8E

Hardware Arduino Due
4

Heh, it always amazes me the # of people who come on the board to ask questions that obviously indicate that they aren't using the Arduino framework at all. Anyway, looking at the Arduino core library source would help here:

Here is the code that Arduino uses to initialize a UART:

  // Configure PMC
  pmc_enable_periph_clk( _dwId ) ;

  // Disable PDC channel
  _pUart->UART_PTCR = UART_PTCR_RXTDIS | UART_PTCR_TXTDIS ;

  // Reset and disable receiver and transmitter
  _pUart->UART_CR = UART_CR_RSTRX | UART_CR_RSTTX | UART_CR_RXDIS | UART_CR_TXDIS ;

  // Configure mode
  _pUart->UART_MR = UART_MR_PAR_NO | UART_MR_CHMODE_NORMAL ;

  // Configure baudrate (asynchronous, no oversampling)
  _pUart->UART_BRGR = (SystemCoreClock / dwBaudRate) >> 4 ;

  // Configure interrupts
  _pUart->UART_IDR = 0xFFFFFFFF;
  _pUart->UART_IER = UART_IER_RXRDY | UART_IER_OVRE | UART_IER_FRAME;

  // Enable UART interrupt in NVIC
  NVIC_EnableIRQ(_dwIrq);

  // Enable receiver and transmitter
  _pUart->UART_CR = UART_CR_RXEN | UART_CR_TXEN ;

You'll notice that you do need to enable the clock first.