Independent key illuminates LED light program design

The independent button type directly uses the I/O line to form a single button circuit. Its characteristic type each button occupies an I/O line, and the operation of each button does not affect the status of other I/O lines. The independent button circuit has flexible configuration and simple software structure, but each button must occupy one I/O port line. Therefore, when there are many buttons, the I/O port line is wasted and should not be used.

Independent button software often uses a query structure. Firstly, the input status of the I/O line is not checked with the bit. If the input of a certain I/O line is low, it can be confirmed that the corresponding button of the I/O line has been pressed, and then Turn to the function handler for this key.

The ideal waveform of a separate keyboard is held low when pressed down, and actually jitter occurs during the rising and falling edges (ie, a small amount of time when the button is pressed and the key is off). There are two ways to debounce, one is through hardware: a capacitor on the circuit; the other is software debounce, adding 10ms delay based on experience.

program:

006.asm

Read the button on the independent keyboard and light the corresponding LED. If there is no button for a while, just cycle the LED.

Wiring: P0 port is connected to eight LEDs

P2 port with eight independent buttons

Timer T0 timing, interrupt mode

************************************************** *************************/

ORG 0000H

LJMP MAIN

ORG 000BH

LJMP INT_T0

ORG 0100H

MAIN: ; main program entry

MOV SP, #50H; set stack

MOV TMOD, #01H ; Set the timing mode

MOV TH0, #15H ;

MOV TL0, #9FH

CLR 20H.0 ; initialization button flag

MOV R2, #0FFH ; Initialization key value

MOV R3, #01H ; Initialize the initial flashing value

MOV R4, #00H ; Initialization timing initial value

SETB TR0; start timer

MOV IE, #82H; open interrupt

LOOP:

LCALL KEY_READ; scan keyboard

L1: JB 20H.0, LIGH; with key input, it will light the corresponding LED

JBC 20H.0, LOOP

MOV A, R4

CJNE A, #0C8H, LOOP; otherwise it is judged whether the timing is up, and the timing is up, the LED is illuminated in eight steps.

LCALL LEED

LJMP L1

/*Lights the corresponding LED*/

LIGH:

MOV A, R2; take the key value

MOV P0, A ; output

RET

/* Cycle lights LED*/

LEED:

MOV A, R3

LOOP1:

CPL A

MOV P0, A

LCALL KEY_READ

JB 20H.0, RETUN0

MOV R0, #0FFH

LCALL DELAY

MOV A, R3

RL A

MOV R3, A

CJNE A, #80H, LOOP1

LOOP2:

CPL A

MOV P0, A

LCALL KEY_READ

JB 20H.0, RETUN0

MOV R0, #0FFH

LCALL DELAY

MOV A, R3

RR A

MOV R3, A

CJNE A, #01H, LOOP2

SJMP LOOP1

RETUN0:

RET

/*Keyboard Scanner*/

KEY_READ:

CLR EA; off timing interrupt when scanning the keyboard

MOV A, P2

CJNE A, #0FFH, DE

LJMP RETUN

DE: MOV R0, #8AH

LCALL DELAY

MOV A, P2

CJNE A, #0FFH, DE0

LJMP RETUN

DE0: MOV R2, A

SETB 20H.0

MOV R4, #00H

DE1: MOV A, P2

CJNE A, #0FFH, DE1

RETUN:

SETB EA

RET

/* interrupt subroutine*/

INT_T0:

CLR EA

PUSH ACC

MOV TH0, #15H ; re-timed initial value

MOV TL0, #9FH

INC R4

POP ACC

SETB EA

RETI

/* Delay subroutine*/

DELAY:

D1: MOV R1, #0FFH

D0: DJNZ R1, D0

DJNZ R0, D1

RET