2020-03-21/矩阵键盘

//矩阵键盘，采用行列扫描
#include<reg51.h>
#define gpio_key P1 
#define smg P0
sbit LSA=P2^2;
sbit LSB=P2^3;
sbit LSC=P2^4;
unsigned char num [16]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
             0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
unsigned char value;//为什么不能用static在按键函数内部定义
void delay(int i)
{
    while(i--);
}
void key(void)
{
    //static unsigned char value;
    int a=0;
    gpio_key=0x0f;//按键不按下，都是高电位，所以用0f判断，而不是f0；
    if(gpio_key!=0x0f)
    {   
        delay(1000);//消抖
        if(gpio_key!=0x0f)
        {   switch(gpio_key)
            {
                case(0x07): value=4;break;
                case(0x0b): value=3;break;
                case(0x0d): value=2;break;
                case(0x0e): value=1;break;
            }
            gpio_key=0xf0;
            if(gpio_key!=0xf0)
            {   
                switch(gpio_key)
                {
                case(0x70): value;break;
                case(0xb0): value+=4;break;
                case(0xd0): value+=8;break;
                case(0xe0): value+=12;break; 
                }
            }
           while((a<50)&&(gpio_key!=0x0f))
           {
                delay(1000);
                a++;
           }
        }
    }
}   


int main()
{   
    while(1){
        LSA=0;
        LSB=0;
        LSC=0;
        key();
        smg=num[value]; 
    }
    return 0;
}