/*******************************************************************************

*                     Demo Program for LaunchPad Board                         *

*             Using S1 at nRST/NMI Pin as Input for Application                *

*                                OCY Oct 2010                                  *

*******************************************************************************/

#include <msp430.h>

#define FLIP_HOLD (0x3300 | WDTHOLD) /* flip HOLD while preserving other bits */

//

#define S1_MAKE P1OUT |= BIT0 /* turn on LED1 for demo */

#define S1_BREAK P1OUT &= ~BIT0 /* turn off LED1 for demo */

//

void main (void)

{

  // We use the red LED1 at P1.0 to demostrate that we can detect

  //    the switch s1 at nRST/NMI pin as an input

  P1OUT &= ~BIT0;

  P1DIR |= BIT0;

  // The WDT will be used exclusively to debounce s1

  WDTCTL = WDTPW | WDTHOLD | WDTNMIES | WDTNMI;

  IFG1 &= ~(WDTIFG | NMIIFG);

  IE1 |= WDTIE | NMIIE;

  // The CPU is free to do other tasks, or go to sleep

  __bis_SR_register(CPUOFF | GIE);

}

//==============================================================================

// isr to detect make/break of s1 at the nRST/NMI pin

#pragma vector = NMI_VECTOR

__interrupt void nmi_isr(void)

{

  if (IFG1 & NMIIFG) // nmi caused by nRST/NMI pin

  {

    IFG1 &= ~NMIIFG;

    if (WDTCTL & WDTNMIES) // falling edge detected 

    {

      S1_MAKE; // tell the rest of the world that s1 is depressed

      WDTCTL = WDT_MDLY_32 | WDTNMI; // debounce and detect rising edge

    }

    else // rising edge detected 

    {

      S1_BREAK; // tell the rest of the world that s1 is released

      WDTCTL = WDT_MDLY_32 | WDTNMIES | WDTNMI; // debounce and detect falling edge

    }

  } // Note that NMIIE is cleared; wdt_isr will set NMIIE 32msec later

  else {/* add code here to handle other kinds of nmi, if any */}

}

//==============================================================================

// WDT is used exclusively to debounce s1 and re-enable NMIIE

#pragma vector = WDT_VECTOR

__interrupt void wdt_isr(void)

{

  WDTCTL ^= FLIP_HOLD; // Flip the HOLD bit only, others remain unchanged

  IFG1 &= NMIIFG; // It may have been set by switch bouncing, clear it

  IE1 |= NMIIE; // Now we can enable nmi to detect the next edge

}

//==============================================================================