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446	Chapter 14

;(0xa to 0xf) then ASCII conversion requires adding

;0x37

sublw

0x09

; 9 - w

;if w from 0 to 9 then 9 - w = positive (C flag = 1)

;if w = 0xa then 9 - 10 = -1 (C flag = 0)

;if w = 0xc then 9 - 12 = -2 (C flag = 0)

btfss	STATUS,C ; Test carry flag
goto	hexLetter	; Carry clear, must be a

letter

;At this point scan code is a decimal digit in the

;range 0 to 9. Convert to ASCII by adding 0x30

movf	scanCode,w	; Recover scan code
addlw	0x30	; Convert to ASCII
goto	displayDig
hexLetter:
movf	scanCode,w	; Recover scan code
addlw	0x37	; Convert to ASCII
displayDig:
; Store so it can be sent
movwf	ascVal
call	send8	; Display routine
call	LCDscroll
call	long_delay	; Debounce
; Recover ASCII
movf	ascVal,w
call	SerialSend
ScanExit:
goto	keyScan	; Continue

;==========================

;calculate scan code ;==========================

;The column position is added to the row code (stored

;in rowCode register). Sum is the scan code

col0:
movf	rowCode,w	; Row code to w
addlw	0x00	; Add 0
movwf	scanCode	; Final value
incf	newScan,f	; New scan code
return
col1:
movf	rowCode,w	; Row code to w
addlw	0x01	; Add 1
movwf	scanCode
incf	newScan,f
return
col2:
movf	rowCode,w	; Row code to w

Communications		447
addlw	0x02	; Add 2
movwf	scanCode
incf	newScan,f
return
col3:
movf	rowCode,w	; Row code to w
addlw	0x03	; Add 3
movwf	scanCode
incf	newScan,f
return
;============================================================
;============================================================
;	L O C A L	P R O C E D U R E S

;============================================================

;==========================

;init LCD for 4-bit mode ;========================== initLCD:

;Initialization for Densitron LCD module as follows:

;4-bit interface

;2 display lines of 16 characters each

;cursor on

;left-to-right increment

;cursor shift right

;no display shift

;=======================\|
;	set command mode		\|
;=======================\|
	bcf		PORTE,E_line		; E line low
	bcf		PORTE,RS_line		; RS line low
	bcf		PORTE,RW_line		; Write mode
	call	delay_125			; delay 125
microseconds
;***********************\|
;	FUNCTION SET		\|
;***********************\|
	movlw	0x28	; 0 0 1 0 1 0 0 0 (FUNCTION SET)
			;	\| \| \| \|__ font select:
			;	\| \| \|	1 = 5x10 in 1/8 or 1/11
			;	\| \| \|	0 = 1/16 dc
			;	\| \| \|___ Duty cycle select
			;	\| \|	0 = 1/8 or 1/11
			;	\| \|	1 = 1/16)
			;	\| \|___ Interface width
			;	\|	0 = 4 bits
			;	\|	1 = 8 bits

448					Chapter 14
			;	\|___ FUNCTION SET COMMAND
	call	send8	; 4-bit send routine
; Set 4-bit mode command must be repeated
	movlw	0x28
	call	send8
;***********************\|
; DISPLAY AND CURSOR ON \|
;***********************\|
	movlw	0x0e	; 0 0 0 0 1 1 1 0 (DISPLAY ON/OFF)
			;	\| \| \| \|___ Blink character
			;	\| \| \|	1 = on, 0 = off
			;	\| \| \|___ Cursor on/off
			;	\| \|	1 = on, 0 = off
			;	\| \|____ Display on/off
			;	\|	1 = on, 0 = off
			;	\|____ COMMAND BIT
	call	send8
;***********************\|
;	set entry mode		\|
;***********************\|
	movlw	0x06	; 0 0 0 0 0 1 1 0 (ENTRY MODE SET)
			;	\| \| \|___ display shift
			;	\| \|	1 = shift
			;	\| \|	0 = no shift
			;	\| \|____ increment mode
			;	\|	1 = left-to-right
			;	\|	0 = right-to-left
			;	\|___ COMMAND BIT
	call	send8
;***********************\|
; cursor/display shift			\|
;***********************\|
	movlw	0x14	; 0 0 0 1 0 1 0 0 (CURSOR/DISPLAY
SHIFT)
			;	\| \| \| \|_\|___ don’t care
			;	\| \|_\|__ cursor/display shift
			;	\|	00 = cursor shift left
			;	\|	01 = cursor shift right
			;	\|	10 = cursor and display
			;	\|	shifted left
			;	\|	11 = cursor and display
			;	\|	shifted right
			;	\|___ COMMAND BIT

call send8 ;***********************|

Communications				449
;	clear display		\|
;***********************\|
	movlw	0x01	; 0 0 0 0 0 0 0	1 (CLEAR DISPLAY)
			;	\|___ COMMAND BIT
	call	send8
; Per documentation
	call	delay_5	; Test for busy
	return

;=======================

;Procedure to delay

;42 microseconds ;======================= delay_125:

movlw	D’42’	; Repeat 42 machine cycles
movwf	count1	; Store value in counter
repeat:
decfsz	count1,f	; Decrement counter
goto	repeat	; Continue if not 0
return		; End of delay

;=======================

;Procedure to delay

;5 milliseconds ;======================= delay_5:

	movlw	D’42’	; Counter = 41
	movwf	count2	; Store in variable
delay:
	call	delay_125	; Delay
	decfsz	count2,f	; 40 times = 5 milliseconds
	goto	delay
	return		; End of delay
;========================
;	pulse E line
;========================
pulseE
	bsf	PORTE,E_line	; Pulse E line
	nop
	bcf	PORTE,E_line
	return
;=============================
;	long delay sub-routine
;=============================
long_delay
	movlw	D’200’	; w delay count
	movwf	J	; J = w

450		Chapter 14
jloop:
movwf	K	; K = w
kloop:
decfsz	K,f	; K = K-1, skip next if zero
goto	kloop
decfsz	J,f	; J = J-1, skip next if zero
goto	jloop
return

;========================

;send 2 nibbles in

;4-bit mode ;========================

;Procedure to send two 4-bit values to Port-B lines

;7, 6, 5, and 4. High-order nibble is sent first

;ON ENTRY:

;w register holds 8-bit value to send

send8:

movwf	store1	; Save	original value
call	merge4	; Merge with Port-B
; Now w has merged byte
movwf	PORTD	; w to	Port D
call	pulseE	; Send	data to LCD
; High nibble is sent
movf	store1,w	; Recover byte into w
swapf	store1,w	; Swap	nibbles in w
call	merge4
movwf	PORTD
call	pulseE	; Send	data to LCD
call	delay_125
return