msp430x54x_uscia0_uart_04.c

MSP430F5XXX的sample code

//******************************************************************************
//   msp430FG5438 Demo - USCI_A0, 9600 UART, SMCLK, LPM0, Echo with over-sampling
//
//   Description: Echo a received character, RX ISR used. Normal mode is LPM0.
//   USCI_A0 RX interrupt triggers TX Echo.
//   Baud rate divider with 1MHz = 1MHz/9600 = ~104.2
//   ACLK = n/a, MCLK = SMCLK = CALxxx_1MHZ = 1MHz
//
//                 msp430FG5438
//             -----------------
//         /|\|                 |
//          | |                 |
//          --|RST              |
//            |                 |
//            |     P3.4/UCA0TXD|------------>
//            |                 | 9600 - 8N1
//            |     P3.5/UCA0RXD|<------------
//
//   M Smertneck
//   Texas Instruments Inc.
//   April 2008
//   Built with CCEv3.2 IAR Embedded Workbench Version: 3.42A
//******************************************************************************

#include <msp430x54x.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P3SEL = 0x30;                             // P3.4,5 = USCI_A0 TXD/RXD
  UCA0CTL1 |= UCSSEL_2;                     // SMCLK
  UCA0BR0 = 6;                              // 1MHz 9600
  UCA0BR1 = 0;                              // 1MHz 9600
  UCA0MCTL = UCBRF3 + UCOS16;               // Modln UCBRSx=1, over sampling
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt

  __bis_SR_register(LPM0_bits + GIE);       // Enter LPM0, interrupts enabled
}

// Echo back RXed character, confirm TX buffer is ready first
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI0_ISR(void)
{
  while (!(SFRIFG1&UCTXIFG));               // USCI_A0 TX buffer ready?
  UCA0TXBUF = UCA0RXBUF;                    // TX -> RXed character
}