Luminary Micro Cortex-M3 UART H/W FIFO 사용하기

Luminary Micro Cortex-M3 UART H/W FIFO 사용하기

Luminary Micro Cortex-M3 는 H/W UART FIFO가 있어 UART처리가 상당히 편리하다.

FIFO Operation

The UART has two 16-entry FIFOs; one for transmit and one for receive. Both FIFOs are accessed via the UART Data (UARTDR) register (see page 261). Read operations of the UARTDR register return a 12-bit value consisting of 8 data bits and 4 error flags while write operations place 8-bit data in the transmit FIFO.
Out of reset, both FIFOs are disabled and act as 1-byte-deep holding registers. The FIFOs are enabled by setting the FEN bit in ARTLCRH (page 269).
FIFO status can be monitored via the UART Flag (UARTFR) register (see page 265) and the UART Receive Status (UARTRSR) register. Hardware monitors empty, full and overrun conditions. The UARTFR register contains empty and full flags (TXFE, TXFF, RXFE, and RXFF bits) and the UARTRSR register shows overrun status via the OE bit.
The trigger points at which the FIFOs generate interrupts is controlled via the UART Interrupt FIFO Level Select (UARTIFLS) register (see page 272). Both FIFOs can be individually configured to trigger interrupts at different levels. Available configurations include 1/8, ¼, ½, ¾, and 7/8. For example, if the ¼ option is selected for the receive FIFO, the UART generates a receive interrupt after 4 data bytes are received. Out of reset, both FIFOs are configured to trigger an interrupt at the ½ mark

LM3S608 UART FIFO 테스트 예제 코드
기존 S/W FIFO를 만들어 사용하던 코드를 그대로 사용하기 위해 #define문으로 코드를 약간 수정하였다.

#define IsRingEmpty()               !UARTCharsAvail(UART0_BASE)
#define GetRingBuffer()             UARTCharGetNonBlocking(UART0_BASE)

void UARTIntHandler1(void)
{
    unsigned long ulStatus;

      // Get the interrrupt status.
      ulStatus = UARTIntStatus(UART0_BASE, true);

      // Clear the asserted interrupts.
      UARTIntClear(UART0_BASE, ulStatus);

     ProcessDataPacket();
}

void ProcessDataPacket(void)
{
 unsigned char rx_data;

  //수신패킷 처리
  if(!IsRingEmpty())
  {
   rx_data = GetRingBuffer();
         :
  }
}