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Connecting a keypad to 8051 - request for help

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Rizwanishaq

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74hc922

Can anyone help me connecting of the keypad to the 8051 and give the program
 

4x4 keypad to mc

select one row and then scan all the columns.
Select another row and again.
Full scan say every 100ms.
If pressed, check twice after 10ms.
 
keypad 4x4 read pc serial

if you want to avoid the keypad algo and read simply by the port, then use 74HC922/74923. I have used this with AVR. See
**broken link removed**

Bibin John
www.bibinjohn.tk
 

keypad in c

This code reads 4x4 keypad ..
If you don't need serial/parallel output - remove relevant sections ..

Regards,
IanP
Code:
$NOPAGING
$MOD252

;---------------------------------------------------------------------------------------------------------------------
;Code: 4x4 matrix key pad
;Inputs: hex keypad via port1
;Outputs: ASCII value of pressed button is sent through the serial port and also the hex equivalent is ouput thru p3.5 to p3.2
;--------------------------------------------------------------------------------------------------------------------                

			ROW0	EQU          P1.0
			ROW1	EQU          P1.1
			ROW2	EQU          P1.2            
			ROW3	EQU          P1.3

			CLMN0	EQU          P1.7
			CLMN1	EQU          P1.6
			CLMN2	EQU          P1.5
			CLMN3	EQU          P1.4

			DIGIT	DATA         30h    			;temporary storage of pressed key ..
			ALERT	EQU          P3.7   			;goes low when any key's pressed ..



			ORG	0000h

			LJMP	Ks_Main

			ORG	0030h

;_________________________________________________________________
;----------SERIAL PORT INITIALISATION STARTS HERE-----------------
;_________________________________________________________________


S9k_Main:		MOV	TMOD,#20h         			;timer_0 in mode2 (8bit auto reload) ..
			MOV	TH1,#0fdh					;set baud to 9600 ..
			MOV	SCON,#50h					;serial mode1 (8bit data varialble baud) ..
			SETB	TR1						;start timer_0 ..
			RET

;--------------SERIAL TRANSMIT SUBROUTINE-------------------------

Tx_Main:		MOV	SBUF, A
Tx_Loop:		JNB	TI, Tx_Loop
			CLR	TI
			RET

;--------------SERIAL RECIEVE SUBROUTINE--------------------------



Rx_Main:		CLR	A
Rx_Loop:		JNB	RI, Rx_Loop
			MOV	A, SBUF
			CLR	RI
			RET

;----------------------20ms delay---------------------------------

Delay_20ms:		;PUSH	R0
			;PUSH	R1
			MOV	R0, #36
Delay_20ms_Loop1:	MOV	R1, #255
Delay_20ms_Loop2:	DJNZ	R1, Delay_20ms_Loop2
			DJNZ	R0, Delay_20ms_Loop1 
			;POP	R1
			;POP	R0
			RET

;------------------------display subroutine--------------------------------

Disp_Message:	PUSH	ACC

Disp_M_Loop1:	MOV	A, #00h					; reset accumulator ..	
			MOVC	A, @A+DPTR
			CJNE	A, #00h, Disp_M_Loop2

			POP	ACC
			RET

Disp_M_Loop2:	MOV	SBUF, A
			LCALL	Tx_Main
			INC	DPTR
			LJMP	Disp_M_Loop1
		            
Disp_Pressed:	DB	'   Key pressed is:  ', 00h


;----------------packed ascii to hex conversion------------------

Ascii2hex:       	PUSH	ACC
                  
			MOV	A, DIGIT
			SUBB	A, #30h
			MOV	B, A
			ANL	A, #10h
			CJNE	A, #00h,Ascii2hex_Loop2
			MOV	B, A
				
Ascii2hex_Loop1:	MOV	DIGIT, A
			POP	ACC
			RET

Ascii2hex_Loop2:	MOV	A, DIGIT
			SUBB	A, #37h
			SJMP	Ascii2hex_Loop1


;------------------send pressed button via p3----------------------

Send4x4_Parallel: PUSH	ACC
			MOV	A, DIGIT
					 
			RRC	A
			MOV	P3.5, C						; LSB ..
			RRC	A
			MOV	P3.4, C
			RRC	A 
			MOV	P3.3, C
			RRC	A
			MOV	P3.2, C						; MSB ..
				 
			POP	ACC
			RET

;_________________________________________________________________
;-------------------------main code------------------------------
;_________________________________________________________________


Ks_Main:		MOV	P1, #0FFh						; Make input ports ..
            		;mov p3,#00h	;make output ports; never make this mistake => 3.0 n 3.1 are serial pins
			SETB	ALERT						              
            	LCALL	S9k_Main
Ks_Main1:		MOV	P1, #0F0h						; all columns high n rows low ..
            	MOV	A, P1
			ANL	A, #11110000b					; consider only columns ..
			CJNE	A, #11110000b, Ks_Main1				; initially check for all keys released ..

;-------------------------------------------------------------------                      

Ks_Loop1:		LCALL	Delay_20ms
			MOV	A, P1
			ANL	A, #11110000b					; scan columns ..
			CJNE	A, #11110000b, Debounce				; if key pressed, check debounce ..
			SJMP	Ks_Loop1						; if not, keep checking for key pressed ..

;-------------------------------------------------------------------

Debounce:		LCALL	Delay_20ms
			MOV	A, P1
			ANL	A, #11110000b 
			CJNE	A, #11110000b,Check_Row
			SJMP	Ks_Loop1

;--------------------------------------------------------------------

Check_Row:		MOV	DPTR, #Disp_Pressed
			LCALL	Disp_Message
				
			CLR	ROW0
			SETB	ROW1
			SETB	ROW2
			SETB	ROW3

			MOV	A, P1
			ANL	A, #11111110b 			 		; test row zero ..
 			CJNE	A, #11111110b, Row_0

;--------------------------------------------------------------------			

			SETB	ROW0
			CLR	ROW1
			SETB	ROW2
			SETB	ROW3

			MOV	A, P1
 			ANL	A, #11111101b 					 ; test row one ..
 			CJNE	A, #11111101b, Row_1

;---------------------------------------------------------------------
			SETB	ROW0
			SETB	ROW1
			CLR	ROW2
			SETB	ROW3

			MOV	A, P1
 			ANL	A, #11111011b					; test row two ..
			CJNE	A, #11111011b, Row_2

;--------------------------------------------------------------------- 			
			SETB	ROW0
			SETB	ROW1
			SETB	ROW2
			CLR	ROW3

			MOV	A, P1
			ANL	A, #11110111b					; test row three ..
			CJNE	A, #11110111b, Row_3

;----------------------------------------------------------------------

			SJMP	Ks_Loop1

;----------------------------------------------------------------------

Row_0:		MOV	DPTR, #Disp_Kcode0
			SJMP	Find_Num

Row_1:		MOV	DPTR, #Disp_Kcode1
			SJMP	Find_Num

Row_2:		MOV	DPTR, #Disp_Kcode2
			SJMP	Find_Num

Row_3:		MOV	DPTR, #Disp_Kcode3
			SJMP	Find_Num

;----------------------------------------------------------------------

Find_Num:		RLC	A
			JNC	Found_Num						; which column is pressed/grounded ..
			INC	DPTR
			SJMP	Find_Num

;----------------------------------------------------------------------

Found_Num:		CLR	ALERT							; notify main MC that key has been pressed ..
            
			CLR	A
			MOVC	A, @A+DPTR
			MOV	DIGIT, A
			LCALL	Tx_Main						; send pressed button to serial port ..
			LCALL	Ascii2hex
			LCALL	Send4x4_Parallel

			SETB	ALERT							; bring keypad module to waiting state ..

;-----------------------------------------------------------------------
 
			LJMP	Ks_Main1

;-----------------------------------------------------------------------
	Disp_Kcode0:	DB '0','1','2','3'
	Disp_Kcode1:	DB '4','5','6','7' 
	Disp_Kcode2:	DB '8','9','A','B' 
	Disp_Kcode3:	DB 'C','D','E','F' 
;-----------------------------------------------------------------------

			END
 
ascii2hex.c

hi all
any one help me

to connect the AT pc keyboard to the at89c51
 

mov a,p1 debouncing

Thanks to, IanP


I try it and working properly.

Nice work


Best Regards
 

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