原创 9．一键多功能按键识别技术

1．实验任务<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

如图4.9.1所示，开关SP1接在P3.7/RD管脚上，在AT89S51单片机的P1端口接有四个发光二极管，上电的时候，L1接在P1.0管脚上的发光二极管在闪烁，当每一次按下开关SP1的时候，L2接在P1.1管脚上的发光二极管在闪烁，再按下开关SP1的时候，L3接在P1.2管脚上的发光二极管在闪烁，再按下开关SP1的时候，L4接在P1.3管脚上的发光二极管在闪烁，再按下开关SP1的时候，又轮到L1在闪烁了，如此轮流下去。

2．电路原理图

3、实现程序

1．汇编源程序

ID                                 EQU 30H

SP1                               BIT P3.7

L1                                 BIT P1.0

L2                                 BIT P1.1

L3                                 BIT P1.2

L4                                 BIT P1.3

                                     ORG 0

                                     MOV ID,#00H

START:                        JB K1,REL

                                     LCALL DELAY10MS

                                     JB K1,REL

                                     INC ID

                                     MOV A,ID

                                     CJNE A,#04,REL

                                     MOV ID,#00H

REL:                    JNB K1,$

                                     MOV A,ID

                                     CJNE A,#00H,IS0

                                     CPL L1

                                     LCALL DELAY

                                     SJMP START

IS0:                               CJNE A,#01H,IS1

                                     CPL L2

                                     LCALL DELAY

                                     SJMP START

IS1:                               CJNE A,#02H,IS2

                                     CPL L3

                                     LCALL DELAY

                                     SJMP START

IS2:                               CJNE A,#03H,IS3

                                     CPL L4

                                     LCALL DELAY

                                     SJMP START

IS3:                               LJMP START

DELAY10MS:    MOV R6,#20

LOOP1:                        MOV R7,#248

                                     DJNZ R7,$

                                     DJNZ R6,LOOP1

                                     RET

DELAY:                        MOV R5,#20

LOOP2:                        LCALL DELAY10MS

                                     DJNZ R5,LOOP2

                                     RET

                                     END

2．C语言源程序

#include <AT89X51.H>

unsigned char ID;

void delay10ms(void)

{

  unsigned char i,j;

  for(i=20;i>0;i--)

  for(j=248;j>0;j--);

}

void delay02s(void)

{

  unsigned char i;

  for(i=20;i>0;i--)

    {delay10ms();

    }

}

void main(void)

{ while(1)

    { if(P3_7==0)

        {delay10ms();

          if(P3_7==0)

            {

              <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />ID++;

              if(ID==4)

                {

                  ID=0;

                }

              while(P3_7==0);

            }

        }

      switch(ID)

        { case 0:

            P1_0=~P1_0;

            delay02s();

            break;            //break直接跳出switch

          case 1:

            P1_1=~P1_1;

            delay02s();

            break;

          case 2:

            P1_2=~P1_2;

            delay02s();

            break;

          case 3:

            P1_3=~P1_3;

            delay02s();

            break;

        }

    }

}

注：程序开始按键没有按下，ID=0，if判断中的语句都不执行，直接到switch（）函数，对应ID=0，P1.0取反然后跳出switch（），由于while（1），则继续到if（）函数检测有无按键按下，仍然没有的话，再到switch（）中P1.0取反，即开始是P1.0每间隔0.2S左右闪烁一次。有按键按下时则对应的LED会闪烁。

     程序不足是当程序不能及时反应键盘的按下，如果快速按下按键，LED会不响应，因为有可能在程序执行延迟函数期间就快速按下和弹起按键了，主程序没有检测到按键