Author: Made by Xura
Date: 2008.8.28
程序描述:利用Timer_A捕获脉冲宽度
利用MSP430单片机定时器A和捕获/比较功能模块结合使用，实现脉冲宽度的测量
程序用到了定时器A的CCI1A端口（MSP430F14X的P1.2引脚）作捕获外部输入
的脉冲电平跳变，start,end,两个个变量来计算脉冲宽度
*******************************************************/
#include "msp430x14x.h"
#include "lcd12864.h"
uint start,end;
uint width; //==用于存放脉宽==
uint period; //==用于存放周期==
uint frequency; //==用于存放频率==
uint fy[7]; //==用于存放频率显示数据==
uint pd[7]; //==用于存放周期显示数据==
uint wh[6]; //==用于存放脉宽显示数据==
const unsigned char zhouqi[]={"周期为:(us) "};
const unsigned char us[]={"us "};
const unsigned char pinlv[]={"频率为:(Hz) "};
const unsigned char hz[]={"HZ "};
void process(void); //==函数声明==
void delay(); //==延时函数==
voidInitSys(); //==初始化时钟==
/******************************************************************
主函数
******************************************************************/
int main( void )
{
WDTCTL = WDTPW + WDTHOLD; //==关狗==

InitSys(); //==初始化时钟,SMCLK,MCLK均为8M==

P1DIR&=~BIT2;
P1SEL = BIT2; //==设置P1.2端口为功能模块使用,即：做捕获源==
TACTL = TASSEL_2+ID_3+TACLR+TAIE+MC1;//==定时器A时钟信号选择SMCLK,8分频,同时设置定时器A计数模式为连续增计模式==

CCTL1 = CM_1+SCS+CAP+CCIE; //==输入上升沿捕获,CCI0A为捕获信号源==
_EINT(); //==开全局中断允许==

Ini_Lcd(); //==初始化液晶==
Clear_GDRAM(); //==清屏==
Disp_HZ(0x80,zhouqi,8);
Disp_HZ(0x88,pinlv,8);

while(1)
{
process();

Write_Cmd(0x90);//==写地址==
Write_Data(0x30+pd[6]);
Write_Data(0x30+pd[5]);
Write_Data(0x30+pd[4]);
Write_Data(0x30+pd[3]);
Write_Data(0x30+pd[2]);
Write_Data(0x30+pd[1]);
Write_Data(0x30+pd[0]);

Write_Cmd(0x98);//==写地址==
Write_Data(0x30+fy[6]);
Write_Data(0x30+fy[5]);
Write_Data(0x30+fy[4]);
Write_Data(0x30+fy[3]);
Write_Data(0x30+fy[2]);
Write_Data(0x30+fy[1]);
Write_Data(0x30+fy[0]);

delay();
}

}

/*******************************************************
初始化时钟
*******************************************************/
voidInitSys()
{
unsignedinti;
//--- 使用XT2振荡器 ---
BCSCTL1&=~XT2OFF;//==打开XT2振荡器==
do
{
IFG1&=~OFIFG;//==清除振荡器失效标志==
for(i=0xFF;i>0;i--);//==延时，等待XT2起振==
}
while((IFG1&OFIFG)!=0);//==判断XT2是否起振==
BCSCTL2=SELM_2+SELS;//==选择MCLK、SMCLK为XT2,8M==
}
/*******************************************************
延时函数
*******************************************************/
voiddelay()
{
unsignedinti;
unsignedintj=10;
for(i=10;i>0;i--)
{
while(j--);
}
}
/********************************************************************
数据处理
********************************************************************/
void process(void)
{
while(end//while(endstart
width = end-start; //==实际脉冲宽度的计算==
period = 2* width;
frequency=1000000/period;

pd[6]=period/1000000;
pd[5]=(period-1000000*pd[6])/100000;
pd[4]=(period-1000000*pd[6]-100000*pd[5])/10000;
pd[3]=(period-1000000*pd[6]-100000*pd[5]-10000*pd[4])/1000;
pd[2]=(period-1000000*pd[6]-100000*pd[5]-10000*pd[4]-1000*pd[3])/100;
pd[1]=(period-1000000*pd[6]-100000*pd[5]-10000*pd[4]-1000*pd[3]-100*pd[2])/10;
pd[0]=period%10;

fy[6]=frequency/1000000;
fy[5]=(frequency-1000000*fy[6])/100000;
fy[4]=(frequency-1000000*fy[6]-100000*fy[5])/10000;
fy[3]=(frequency-1000000*fy[6]-100000*fy[5]-10000*fy[4])/1000;
fy[2]=(frequency-1000000*fy[6]-100000*fy[5]-10000*fy[4]-1000*fy[3])/100;
fy[1]=(frequency-1000000*fy[6]-100000*fy[5]-10000*fy[4]-1000*fy[3]-100*fy[2])/10;
fy[0]=frequency%10;
}
/*******************************************************************
中断处理函数
*******************************************************************/
#pragma vector=TIMERA1_VECTOR //==定时器A中断处理==
__interrupt void timer_a(void)
{
switch(TAIV) //==向量查询==
{ case 2: //==捕获中断==
if(CCTL1&CM0) //==捕获到上升沿==
{
CCTL1=(CCTL1&(~CM0))|CM1; //==更变设置为下降沿触发==

start=TAR; //==记录初始时间==
}

else if (CCTL1&CM1) //==捕获到下降沿==
{
CCTL1=(CCTL1&(~CM1))|CM0; //==更变设置为上升沿触发==
end=TAR; //==用start,end,overflow计算脉冲宽度==

}
break;

default:
break;
}
}