#include <intrinsics.h>
#include <msp430xG46x.h>

void initPort();
void initUSCI();
void initInterrupt();

void main(void)
{
  initPort();
  initUSCI();
  initInterrupt();
  __enable_interrupt();
  
  UCA0TXBUF = '0';
  while(UCA0STAT & 0x1);
  UCA0TXBUF = '1';
  while(UCA0STAT & 0x1);
  UCA0TXBUF = '2';
  while(UCA0STAT & 0x1);
  UCA0TXBUF = '3';
  while(UCA0STAT & 0x1);
  UCA0TXBUF = '4';
  while(UCA0STAT & 0x1);
  while(1);
}

void initPort()
{
  P1DIR = 0x0;    //P1 is input (buttons at P1.0 and P1.1)
  P1SEL = 0x0;    //select I/O for P1
  
  P2OUT = 0;
  P2DIR = 0x6;    //P2.2 and P2.1 are output
  P2SEL = 0x0;    //select I/O for P2
}

void initUSCI()
{
  UCA0CTL1 = 0x1;         //reset USCI
  UCA0CTL0 = 0x0;         //no parity, LSB first, 8 data bits, one stop bit
                          //UART-Mode, asynchronous mode
  UCA0CTL1 |= 0x80;       //SMCLK as clock source
  UCA0BR0 = 0x09;
  UCA0BR1 = 0x00;
  UCA0MCTL = 0x2;           //UCBRSx = 1, UCOS16 = 0, UCBRFx = 0

  P2DIR |= 0x10;          //P2.4 is USCI transmit
  P2DIR &= 0xdf;          //P2.5 is USCI receive
  P2SEL |= 0x30;          //select USCI-function for P2.4
  
  UCA0CTL1 &= 0xfe;       //clear UCSWRST
}

void initInterrupt()
{
  P1IES = 0x3;       //select high-to-low-transition for interrupts
  P1IFG = 0x0;       //make sure no interrupts are pending
  P1IE = 0x3;        //enable interrupts for P1.0 and P1.1
}

#pragma vector=PORT1_VECTOR
__interrupt void port1ISR(void)
{
  if (P1IFG & 0x1)
  {
    //->interrupt on button S1
    UCA0TXBUF = '1';
    P1IFG &= 0xfe;    //reset IRQ-bit
  }
  else if (P1IFG & 0x2)
  {
    //->interrupt on button S2
    UCA0TXBUF = '2';
    P1IFG &= 0xfd;    //reset IRQ-bit
  }
}