采用P1口4x4阵列参考电路

例程:
//*****************************************************************************
#include <msp430x14x.h>
//*****************************************************************************
//IO初始化程序
void Init_Port(void)
{
      //将P1口所有的管脚在初始化的时候设置为输入方式
      P1DIR = 0;
  
      //将P1口所有的管脚设置为一般I/O口
      P1SEL = 0;
     
      // 将P1.4 P1.5 P1.6 P1.7设置为输出方向
      P1DIR |= BIT4;
      P1DIR |= BIT5;
  P1DIR |= BIT6;
      P1DIR |= BIT7;

  //先输出低电平
  P1OUT = 0x00;

  // 将中断寄存器清零
      P1IE = 0;
      P1IES = 0;
      P1IFG = 0;
      //打开管脚的中断功能
  //对应的管脚由高到低电平跳变使相应的标志置位
      P1IE |= BIT0;
      P1IES |= BIT0;
      P1IE |= BIT1;
      P1IES |= BIT1;
  P1IE |= BIT2;
      P1IES |= BIT2;
      P1IE |= BIT3;
      P1IES |= BIT3;
  _EINT();//打开中断
      return;
}
void Delay(void)
{
  int i;
  for(i = 100;i--;i > 0) ;//延时一点时间
}

//*****************************************************************************
//键处理程序
int KeyProcess(void)
{
      int nP10,nP11,nP12,nP13;
  int nRes = 0;
  //P1.4输出低电平
  P1OUT &= ~(BIT4);
  nP10 = P1IN & BIT0;
  if (nP10 == 0) nRes = 13;
  nP11 = P1IN & BIT1;
  if (nP11 == 0) nRes = 14;
  nP12 = P1IN & BIT2;
  if (nP12 == 0) nRes = 15;
  nP13 = P1IN & BIT3;
  if (nP13 == 0) nRes = 16;
  //P1.5输出低电平
  P1OUT &= ~(BIT4);
  nP10 = P1IN & BIT0;
  if (nP10 == 0) nRes = 9;
  nP11 = P1IN & BIT1;
  if (nP11 == 0) nRes = 10;
  nP12 = P1IN & BIT2;
  if (nP12 == 0) nRes = 11;
  nP13 = P1IN & BIT3;
  if (nP13 == 0) nRes = 12;
  //P1.6输出低电平
  P1OUT &= ~(BIT4);
  nP10 = P1IN & BIT0;
  if (nP10 == 0) nRes = 5;
  nP11 = P1IN & BIT1;
  if (nP11 == 0) nRes = 6;
  nP12 = P1IN & BIT2;
  if (nP12 == 0) nRes = 7;
  nP13 = P1IN & BIT3;
  if (nP13 == 0) nRes = 8;
  //P1.7输出低电平
  P1OUT &= ~(BIT4);
  nP10 = P1IN & BIT0;
  if (nP10 == 0) nRes = 1;
  nP11 = P1IN & BIT1;
  if (nP11 == 0) nRes = 2;
  nP12 = P1IN & BIT2;
  if (nP12 == 0) nRes = 3;
  nP13 = P1IN & BIT3;
  if (nP13 == 0) nRes = 4;

  P1OUT = 0x00;//恢复以前值。

  //读取各个管脚的状态
  nP10 = P1IN & BIT0;
  nP11 = P1IN & BIT1;
  nP12 = P1IN & BIT2;
  nP13 = P1IN & BIT3;
  for(;;)
  {
   if(nP10 == 1 && nP11 == 1 && nP12 == 1 && nP13 == 1)
   {
     //等待松开按键
     break;
   }
  }
  return nRes;
}

//*****************************************************************************
// 处理来自端口 1 的中断
interrupt [PORT1_VECTOR] void PORT_ISR(void)
{
  Delay();
  KeyProcess();
      if(P1IFG & BIT0)
      {      
        P1IFG &= ~(BIT0);// 清除中断标志位
      }
      if(P1IFG & BIT1)
      {
        P1IFG &= ~(BIT1);// 清除中断标志位
      }
      if(P1IFG & BIT2)
      {
        P1IFG &= ~(BIT2);// 清除中断标志位
      }
  if(P1IFG & BIT3)
      {
        P1IFG &= ~(BIT3);// 清除中断标志位
      }
}

//*****************************************************************************
//时基初始化程序
void Init_CLK(void)
{
   unsigned int i;
   BCSCTL1 = 0X00;    //将寄存器的内容清零
   //XT2震荡器开启
   //LFTX1工作在低频模式
   //ACLK的分频因子为1      
      do
      {
  IFG1 &= ~OFIFG;                                     // 清除OSCFault标志
  for (i = 0x20; i > 0; i--);                          
      }
      while ((IFG1 & OFIFG) == OFIFG);         // 如果OSCFault =1   
        
      BCSCTL2 = 0X00;    //将寄存器的内容清零
      BCSCTL2 += SELM1;   //MCLK的时钟源为TX2CLK，分频因子为1
      BCSCTL2 += SELS;   //SMCLK的时钟源为TX2CLK，分频因子为1
}