ECE 322 day18

/*
    modified from original:
        msp430fr69xx_p1_03.c
*/

//******************************************************************************
//  MSP430FR69xx Demo - Software Port Interrupt Service on P1.1 from LPM4
//
//  Description: A Hi/Lo transition on P1.1 will trigger P1ISR the first time.
//  On hitting the P1ISR, device exits LPM4 mode and executes section of code in
//  main() which includes toggling an LED and the P1.1 IES bit which switches
//  between Lo/Hi and Hi/Lo trigger transitions to alternatively enter the P1ISR.
//  ACLK = n/a, MCLK = SMCLK = default DCO
//
//
//               MSP430FR6989
//            -----------------
//        /|\|                 |
//         | |                 |
//         --|RST              |
//     /|\   |                 |
//      --o--|P1.1         P1.0|-->LED
//     \|/
//
//   William Goh
//   Texas Instruments Inc.
//   April 2014
//   Built with IAR Embedded Workbench V5.60 & Code Composer Studio V6.0
//******************************************************************************

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW | WDTHOLD;                 // Stop watchdog timer

  /* Question A:
      This example is not great for demonstrating "best practices",
      it is really just the shortest path to getting things set up.

      What is a better way to handle the part of main() that configures
      the peripherals?
  */
  // Configure GPIO
  P1OUT = BIT1;                             // Pull-up resistor on P1.1
  P1REN = BIT1;                             // Select pull-up mode for P1.1
  P1DIR = 0xFF ^ BIT1;                      // Set all but P1.1 to output direction
  P1IES = BIT1;                             // P1.1 Hi/Lo edge
  P1IFG = 0;                                // Clear all P1 interrupt flags
  P1IE = BIT1;                              // P1.1 interrupt enabled

  P2OUT = 0;
  P2DIR = 0xFF;

  P3OUT = 0;
  P3DIR = 0xFF;

  P4OUT = 0;
  P4DIR = 0xFF;

  PJOUT = 0;
  PJDIR = 0xFFFF;




  /* Question B
   *    What is the purpose of the following line again?
   *    Write in your own words what this does and why it's needed.
   */
  PM5CTL0 &= ~LOCKLPM5;




  while(1)
  {

    /* Question C
     *  The following line does two things.  What are they and
     *  what is the net effect in your own words?
     *  (look up SR status register and the #defines)
     */
    __bis_SR_register(LPM4_bits | GIE);     // Enter LPM4 w/interrupt
    __no_operation();                       // For debugger


    /* Question D
     *  Describe what effect the following line has in the system.
     *  Convert to a function call: what is the function name?
     */
    P1OUT ^= BIT0;

    /* Question E
     *  After the above line executes, what is the next CPU instruction?
     */
  }
}



/* Question F
 *  Change the name of this function to be a little bit more
 *  descriptive of its purpose.
 */
// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)

{
  //P1IES ^= BIT1;                            // Toggle interrupt edge
  P1IFG &= ~BIT1;                           // Clear P1.1 IFG
  __bic_SR_register_on_exit(LPM4_bits);     // Exit LPM4
}