MSP430 G2553 LaunchPad GPIO中断

P1、P2端口上的每个管脚都支持外部中断。P1端口的所有管脚都对应同一个中断向量（Interrupt Vector），类似的，P2端口的所有管脚都对应另一个中断向量；通过PxIFG寄存器来判断中断来源于具体哪个管脚。

相关的寄存器如下表所示。

Register	Short Form	Register Type	Initial State
Interrupt Flag	PxIFG	Read/write	Reset with PUC
Interrupt Edge Select	PxIES	Read/write	Unchanged
Interrupt Enable	PxIE	Read/write	Reset with PUC

PxIFG：中断标志，1表示有中断事件待处理

PxIES：中断边沿选择，0表示上升沿触发，1表示下降沿触发

PxIE：GPIO中断使能，0表示禁用，1表示使能

程序示例

利用板上S2按键控制LED1灯闪烁，每按下一次，LED1灯闪烁一次。该程序还缺少按键消抖的功能。（G2 LaunchPad Rev1.5上P1.3没有连接电容及上拉电阻）

#include "io430.h"

#define LED1 BIT0
#define PUSH2 BIT3

//function declarations
void delay(void);

void main(void)
{
    // Stop watchdog timer to prevent time out reset
    WDTCTL = WDTPW + WDTHOLD;
    
    //set P1.3 to input with pullup
    P1OUT = 0;
    P1OUT |= PUSH2; //initialize the pullup state
    P1REN |= PUSH2; //enable internal pullup
    
    //set P1.0 to output
    P1DIR |= LED1; //P1.0 out to LED1, P1.3 remains input for PUSH2 button
    
    //set the interrupt registers
    P1IES |= PUSH2; //select high -> low transition
    P1IFG &= ~PUSH2; //clear the flag for P1.3 before enabling the interrupt,
    // to prevent an immediate interrupt
    P1IE |= PUSH2; //enable interrupt for P1.3
    
    __enable_interrupt(); //turn on the interrupts
    
    while(1)
    {
    }

}

void delay(void)
{
    volatile unsigned int i;
    for(i = 0; i < 50000; i++);
}

//interrupt service routines
#pragma vector  = PORT1_VECTOR
__interrupt void P1_ISR(void)
{
    if((P1IFG & PUSH2) == PUSH2)
    {
        P1IFG &= ~PUSH2; //clear the interrupt flag
        
        P1OUT |= LED1; //turn on LED1
        delay();
        P1OUT &= ~LED1; //turn off LED1
    }
    else
    {
        P1IFG = 0;
    }
}