/******************************************************************
;                                                        
;       Description: MSP430F149 serial link example for CPE496                                                  
;       Date : 02/14/2005                                     
;       Auth : Zexin Pan                                       
; 
 ******************************************************************/

#include "msp430x14x.h"

/* uncomment this to make UART RX interrupt driven */
//#define UART0_INT_DRIVEN_RX

unsigned char thr_char;  /* hold char from UART RX*/
unsigned char rx_flag;   /* receiver rx status flag */

// universal delay function
void Delay(void);

// global clock configuration
void SpeedUpClock(void);  


// UART0 rx int. 
interrupt [UART0RX_VECTOR] void UART0_RX_interrupt(void);
// UART Initializaion
void UART_Initialize(void);
//send char function
void UART0_putchar(char c);            
//receive char function
char UART0_getchar(void);               

void main(void) 
{ 

  
  WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

 
  SpeedUpClock();

  UART_Initialize();
  
  #ifdef UART0_INT_DRIVEN_RX
    rx_flag=0x00;        /* rx default state "empty" */
  #endif
 
  _EINT();       // enable global interrupts
  
   #ifdef UART0_INT_DRIVEN_RX
   while(!(rx_flag&0x01)); /* wait until receive the character from HyperTerminal*/ 
   #else
   thr_char=UART0_getchar();
   #endif

  // send a message
    UART0_putchar('C');
    UART0_putchar('P');
    UART0_putchar('E');
    UART0_putchar('4');
    UART0_putchar('9');
    UART0_putchar('6');

  while(1) 
    {
    Delay();
    UART0_putchar(thr_char);		// send the char we just received!
    }    
}

void SpeedUpClock(void)
{
  IFG2 = 0;
  IFG1 = 0;


  //using a 8MHz clock from LFXT1, and ACLK=LFXT1
  BCSCTL1 |= XTS;

  /*wait in loop until crystal stabalizes*/
  do
  {
    IFG1 &= ~OFIFG;
  }
  while (OFIFG & IFG1);

  Delay();
  //Reset osc. fault flag again
  IFG1 &= ~OFIFG;
}



void Delay(void)
{
  volatile unsigned int delay_count;
  for(delay_count=0xffff;delay_count!=0;delay_count--);
}


void UART_Initialize(void)
{
////////////////////////////////////////////////////////////////
//   UART0 Initialization
////////////////////////////////////////////////////////////////


// UART0 - 38400 bps
//IMPORTANT NOTICE: the following configuration works only for 8MHZ clock rate
// AND 38400 bps baud rate
//you have to recalculate these values if the cpu clock rate or baud rate has changed 
  U0MCTL = 146;
  U0BR0  = 208;
  U0BR1  = 0;

  P3SEL |= 0x30; // bits 4-5 are for special function UART0
  ME1 |= URXE0 + UTXE0; // UART module enable
  U0CTL = CHAR;     /* 8-bit characters */
  U0TCTL = SSEL0; /* clock source ACLK, 8MHZ */
  U0RCTL = 0;
  
  #ifdef UART0_INT_DRIVEN_RX
    IE1 |= URXIE0;  // enable RX interrupts
  #endif
}  //end UART_Initialize()


interrupt [UART0RX_VECTOR] void UART0_RX_interrupt(void)
{
    
  thr_char = U0RXBUF;
  rx_flag=0x01;          // signal main function receiving a char
 }
  

void UART0_putchar(char c)
{

  // wait for other character to transmit
  while (!(IFG1 & UTXIFG0));
  U0TXBUF = c;
}

char UART0_getchar(void)
{

  for (;;)
  {
    if (U0RCTL & RXERR)
    {
      // if you want to answer receive errors, do it here.
      U0RCTL &= ~(FE+PE+OE+BRK+RXERR);
    }
    else
    {
      if (IFG1 & URXIFG0)
      {  // we've received a character
        return U0RXBUF;
      }
    }
  }
}