RM-yahoo-544

3 x 4 keypad source code

This is code for 4 io's for a 3 x 4 keypad based on Mike Rigby Jones Circuit with four diodes. This code works fine on the 877 and gives hex number 1 to 12 for each key. The logic is the same as the original code but avoids tables to make it more sturdy

start: 
	bsf STATUS,RP0
	bcf option_reg,not_rbpu
	bcf STATUS,RP0 
	clrf PORTB 
	call LCD_Clr

find_key
	call scan
	movf keycode,w
	xorlw 0x00
	btfsc status,z
	goto find_key
	movf keycode,w
	call LCD_HEX


key_off	call scan
	movf keycode,w
	xorlw 0x00
	btfsc status,z
	goto find_key
	goto key_off 

scan: 
	movlw B'00001110'
	movwf PORTB
	bsf STATUS,RP0 		; bank 1
	movwf TRISB 		; turn B0 to an output (low)
	bcf STATUS,RP0 		; bank 0
	movf PORTB,W 		; get port b state
	andlw 0x0f 		; mask lower nibble
	movwf keys
	xorlw B'00001110'
	btfsc status,z
	goto row2

row1_1	movf keys,w
	xorlw 0x0C
	btfss status,Z
	goto row1_2
	movlw 0x0A
	movwf keycode
	return

row1_2	movf keys,w
	xorlw 0x08
	btfss status,Z
	goto row1_3
	movlw 0x0B
	movwf keycode
	return

row1_3	movf keys,w
	xorlw 0x0A
	btfss status,Z
	goto no_key
	movlw 0x0C
	movwf keycode
	return

row2	movlw B'00001101'
	movwf PORTB
	bsf STATUS,RP0 		; bank 1
	movwf TRISB 		; turn B0 to an output (low)
	bcf STATUS,RP0 		; bank 0
	movf PORTB,W 		; get port b state
	andlw 0x0f
	movwf keys
	xorlw B'00001101'
	btfsc status,z
	goto row3

	row2_1 movf keys,w
	xorlw 0x0C
	btfss status,Z
	goto row2_2
	movlw 0x07
	movwf keycode
	return

row2_2	movf keys,w
	xorlw 0x09
	btfss status,Z
	goto row2_3
	movlw 0x08
	movwf keycode
	return

row2_3	movf keys,w
	xorlw 0x08
	btfss status,Z
	goto no_key
	movlw 0x09
	movwf keycode
	return

row3	movlw B'00001011'
	movwf PORTB
	bsf STATUS,RP0 		; bank 1
	movwf TRISB 		; turn B0 to an output (low)
	bcf STATUS,RP0 		; bank 0
	movf PORTB,W 		; get port b state
	andlw 0x0f 		; mask lower nibble
	movwf keys
	xorlw B'00001011'
	btfsc status,z
	goto row4

row3_1	movf keys,w
	xorlw 0x08
	btfss status,Z
	goto row3_2
	movlw 0x04
	movwf keycode
	return

row3_2	movf keys,w
	xorlw 0x09
	btfss status,Z
	goto row3_3
	movlw 0x05
	movwf keycode
	return

row3_3	movf keys,w
	xorlw 0x0A
	btfss status,Z
	goto no_key
	movlw 0x06
	movwf keycode
	return

row4	movlw B'00000111'
	movwf PORTB
	bsf STATUS,RP0 		; bank 1
	movwf TRISB 		; turn B0 to an output (low)
	bcf STATUS,RP0 		; bank 0
	movf PORTB,W 		; get port b state
	andlw 0x0f 		; mask lower nibble
	movwf keys
	xorlw B'00000111'
	btfsc status,z
	goto no_key

row4_1	movf keys,w
	xorlw 0x04
	btfss status,Z
	goto row4_2
	movlw 0x01
	movwf keycode
	return

row4_2	movf keys,w
	xorlw 0x01
	btfss status,Z
	goto row4_3
	movlw 0x02
	movwf keycode
	return

row4_3	movf keys,w
	xorlw 0x02
	btfss status,Z
	goto no_key
	movlw 0x03
	movwf keycode
	return

no_key	clrf keycode
	return

END