key.c

基于PROTERUS仿真的AVR例子

#define KEY_C
#include "includes.h"


char read_keybord(void)
{
    static char key_state = 0;
    static char key_value, key_line;
    static char key_return = NO_KEY;
    unsigned char i;
    switch(key_state)
    {
        case 0:
            key_line = 0x08;      //0b0000 1000;
            for(i=1;i<=4;i++)    //按键扫描
            {
                KEY_PORT = ~key_line;   //输出行线电平                
                KEY_PORT = ~key_line;   //输出两次
                key_value = KEY_MASK & KEY_PIN;  //读列电平
                if(key_value == KEY_MASK)
                {
                    key_line <<= 1;   //没有按键,继续扫描  
                }
                else
                {
                    key_state++;  //有键按下,停止扫描
                    break;    //转消抖确认状态
                }                
                
            }
            break;
        case 1:
            {
                switch((key_value | key_line)) //与状态0相同,确认按键
                {
                    case 0x0e:              //0b00001110:
                        key_return = K1_1;
                        break;
                    case 0x0d:              //0b00001101:
                        key_return = K1_2;
                        break;
                    case 0x0b:              //0b00001011:
                        key_return = K1_3;
                        break;                   
      
                    case 0x16:              //0b00010110:
                        key_return = K2_1;
                        break;
                    case 0x15:              //0b00010101:
                        key_return = K2_2;
                        break;
                    case 0x13:              //0b00010011:
                        key_return = K2_3;
                        break;                  
                        
                    case 0x26:              //0b00100110:
                        key_return = K3_1;
                        break;
                    case 0x25:              //0b00100101:
                        key_return = K3_2;
                        break;
                    case 0x23:              //0b00100011:
                        key_return = K3_3;
                        break;                    
                        
                    case 0x46:              //0b01000110:
                        key_return = K4_1;
                        break;
                    case 0x45:              //0b01000101:
                        key_return = K4_2;
                        break;
                    case 0x43:              //0b01000011:
                        key_return = K4_3;
                        break;                   
                }
               key_state++;     //转入按键释放状态                                
            }
            break;
        case 2:     //等待按键释放
            KEY_PORT = 0x07;      //行线全部输出低电平      
            KEY_PORT = 0x07;
            if((KEY_MASK & KEY_PIN) == KEY_MASK)
            {
                key_state = 0;   //列线全部为高电平,返回状态0
            }     
            break; 
    }
    return(key_return);
}