初始时KC0-KC3,KRO-KR4都为低电平，先让KRO-KR4为高电平，读KC0-KC3的值，有键按下的话，KC0-KC3
中一定会有一个为高电平，确定后，依次再让KRO-KR4为高电平，从而确定键值
#include <stdio.h>
#include <absacc.h>
#include <./Atmel/at89x52.h>
extern void start_t2imer(void);
unsigned char scankey;
bit Timerout=0;
bit keypress;
#define KR0 P1_0
#define KR1 P1_1
#define KR2 P1_2
#define KR3 P1_3
#define KC0 P1_4
#define KC1 P1_5
#define KC2 P1_6
#define KC3 P1_7
#define KBD_PORT P1
#define FSM_INIT 0X00
#define FSM_WAIT_PRESS 0X01
#define FSM_VERFY1 0X02
#define FSM_VERFY2 0X03
#define FSM_WAIT_RELESE 0X04
#define KBD_VAL_VAILD 0X80
main(){
unsigned char fsm_key=0;
unsigned char kbd_col;
unsigned char kbd_row;
unsigned char key_val;
IE=0X40;
start_t2imer();
EA=1; /* Enable interrupts */
while(1){ /*10ms扫描一次键盘程序*/
if(Timerout){
Timerout=0;
switch(fsm_key){
case FSM_INIT: /*初始扫秒状态*/
KR0=1;
KR1=1;
KR2=1;
KR3=1;
fsm_key=FSM_WAIT_PRESS;
break;
case FSM_WAIT_PRESS:
if(keypress){
key_val=0; /清除以前的键值/
if(KC0){
KC0=1;
kbd_col=1;
}
else if(KC1){
KC1=1;
kbd_col=2;
}
else if(KC2){
KC2=1;
kbd_col=3;
}
else if(KC3){
KC3=1;
kbd_col=4;
}
else{ /*干挠信号的话就重回初始扫描状态*/
fsm_key=FSM_INIT;
}
kbd_row =KBD_PORT;
kbd_row >>=4;
if(kbd_row){
if(KR0){
kbd_row=0;
fsm_key=FSM_VERFY1; /*转去抖动*/
}
else if(KR1){
kbd_row=4;
fsm_key=FSM_VERFY1;
}
else if(KR2){
kbd_row=8;
fsm_key=FSM_VERFY1;
}
else if(KR3){
kbd_row=12;
fsm_key=FSM_VERFY1;
}
else{
fsm_key=FSM_INIT;
}
}
else{
fsm_key=FSM_INIT;
}
}
break;
case FSM_VERFY1: /*去抖动*/
switch(kbd_row){
case 0:
if(KR0) fsm_key=FSM_VERFY2;
else fsm_key=FSM_INIT;
break;
case 4:
if(KR1) fsm_key=FSM_VERFY2;
else fsm_key=FSM_INIT;
break;
case 8:
if(KR2) fsm_key=FSM_VERFY2;
else fsm_key=FSM_INIT;
break;
case 12:
if(KR3) fsm_key=FSM_VERFY2;
else fsm_key=FSM_INIT;
break;
default:
fsm_key=FSM_INIT;
break;
}
break;
case FSM_VERFY2: /*去抖动计算键值*/
switch(kbd_row){
case 0:
if(KR0) key_val=(kbd_row+kbd_col)|KBD_VAL_VAILD;
break;
case 4:
if(KR1) key_val=(kbd_row+kbd_col)|KBD_VAL_VAILD;
break;
case 8:
if(KR2) key_val=(kbd_row+kbd_col)|KBD_VAL_VAILD;
break;
case 12:
if(KR3) key_val=(kbd_row+kbd_col)|KBD_VAL_VAILD;
break;
default:
break;
}
KR0=1;
KR1=1;
KR2=1;
KR3=1;
fsm_key=FSM_WAIT_RELESE;
break;
case FSM_WAIT_RELESE: /*键盘释放*/
if(!keypress){
fsm_key=FSM_INIT;
}
break;
default:
fsm_key=FSM_INIT;
break;
}
}
}
}
void time2()interrupt 5 {//base 10 ms
TF2=0;
Timerout=1;
scankey=KBD_PORT;
if(scankey&0x0f){
keypress=1;
}
else{
keypress=0;
}
}
帮我解释一下程序，尤其始那个键值的计算不懂 |
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