lcd.asm

sensor of ultrasonic parking sensor

;************************************************
;* LCD.ASM                                      *
;************************************************
;* Contains subroutines to control an external  *
;* lcd panel in 4-bit mode.  These routines     *
;* were designed specifically for the panel on  *
;* the MCU201 workshop demo board, but should   *
;* work with other LCDs with a HD44780 type     *
;* controller.                                  *
;* Routines include:                            *
;*   - InitLCD to initialize the LCD panel      *
;*   - putcLCD to write a character to LCD      *
;*   - SendCmd to write a command to LCD        *
;*   - clrLCD to clear the LCD display          *
;*   - L1homeLCD to return cursor to line 1 home*
;*   - L2homeLCD to return cursor to line 2 home*
;*   - PutHexLCD to write a HEX Code to LCD     *
;*   - Hex2ASCII to convert 4 bits to ASCII Code*
;************************************************
;
		list	p=16f877
		#include <p16f877.inc>	
;
; Defines for I/O ports that provide LCD data & control
; PORTB.0 - PORTB.3 are Data Pins for LCD Module
; PORTB.4 is E Control Signal for LCD
; PORTB.5 is RS Control Signal for LCD
; PORTC.2 is BackLight Control pin for LCD Module 
;
		global	InitLCD
		global	putcLCD
		global	clrLCD
		global	L1homeLCD
		global	L2homeLCD
		global  SendCmd
		global	PutHexLCD
		global	Hex2ASCII
;
LCD_DATA	equ	PORTB
LCD_CNTL	equ	PORTB

; Defines for I/O pins that provide LCD control
RS		equ	5
E		equ	4

; LCD Module commands
DISP_ON		EQU	0x00C	; Display on
DISP_ON_C	EQU	0x00E	; Display on, Cursor on
DISP_ON_B	EQU	0x00F	; Display on, Cursor on, Blink cursor
DISP_OFF	EQU	0x008	; Display off
CLR_DISP	EQU	0x001	; Clear the Display
ENTRY_INC	EQU	0x006	;
ENTRY_INC_S	EQU	0x007	;
ENTRY_DEC	EQU	0x004	;
ENTRY_DEC_S	EQU	0x005	;
DD_RAM_ADDR	EQU	0x080	; Least Significant 7-bit are for address
DD_RAM_UL	EQU	0x080	; Upper Left coner of the Display
;

; Directs linker to provide 4 variables in GPR memory
		UDATA
Byte		RES	1
Byte1		RES	1
Count		RES	1
Count1		RES	1
W_BUFR		RES	1
Hex_Bfr	 	RES	1
;
LCD_CODE 	CODE		
;*******************************************************************
;* The LCD Module Subroutines                                      *
;* Command sequence for 2 lines of 5x16 characters                 *
;*******************************************************************
InitLCD
		BANKSEL	TRISB
		movlw	0xc0		; Initialize inputs/outputs for LCD
		movwf	TRISB
		BANKSEL	LCD_DATA
		clrf	LCD_DATA	; Clear LCD data & control bits
;
		movlw	.50		; Power=On delay 50mS
		Call 	Delay_MS
;
		movlw   0x02		; Init for 4-bit interface
		call	Send_4bit
		movlw	.10		;  Delay 10 mS
		Call 	Delay_MS
;
		movlw	b'00000011'	; Fully Initial LCD module 
		call	Send_4bit	; Sent '0011' data 4 time
		movlw	.5		; Delay 5mS
		Call 	Delay_MS
		movlw	b'00000011'
		call	Send_4bit
		call	Delay_1MS	; Delay 1mS
 		movlw	b'00000011'
 		call	Send_4bit
 		movlw	b'00000011'
 		call	Send_4bit	
;
		movlw	b'00101000'	; Set 2 lines & 5 x 7 dots
		call	SendCmd
		movlw	DISP_ON		; Turn display on (0x0C)
		call	SendCmd
		movlw	ENTRY_INC	; Configure cursor movement
		call	SendCmd
		movlw	DD_RAM_ADDR	; Set writes for display memory
		call	SendCmd
		return
;
;*******************************************************************
;*SendChar - Sends character to LCD                                *
;*This routine splits the character into the upper and lower       * 
;*nibbles and sends them to the LCD, upper nibble first.           *
;*******************************************************************
putcLCD
		banksel	Byte
		movwf	Byte		; Save WREG in Byte variable
		call	Delay_1MS
		swapf	Byte,W		; Write upper nibble first
		andlw	0x0f
		movwf	LCD_DATA
		bsf	LCD_CNTL, RS	; Set for data
		bsf	LCD_CNTL, E	; Clock nibble into LCD
		bcf	LCD_CNTL, E
		movf	Byte,W		; Write lower nibble last
		andlw	0x0f
		movwf	LCD_DATA
		bsf	LCD_CNTL, RS	; Set for data
		bsf	LCD_CNTL, E	; Clock nibble into LCD
		bcf	LCD_CNTL, E
		return
;
;*********************************************************************
;*      To put the HEX value to LCD Display ,,
;*      High nibble first than Low nibble 
;*      Input : W Reg.
;*********************************************************************
PutHexLCD
		banksel	W_BUFR
		movwf	W_BUFR		; Save W Register !!
		swapf	W_BUFR,W		; High nibble first !!	
		call	Hex2ASCII
		call	putcLCD
;
		movf	W_BUFR,W
		call	Hex2ASCII
		call	putcLCD
		return
;
;******************************************************************
;*       Convert a low nibble to ASCII code
;*       Input : W Reg.
;*       Output: W Reg.
;******************************************************************
Hex2ASCII
		andlw	0x0f		; Mask Bit 4 to 7
		movwf	Hex_Bfr
		sublw	.09
		btfsc	STATUS,C	; If W less than A (C=1) --> only add 30h
		goto	Add_W_30  
Add_W_37	movlw	0x37
		goto	Hex_cont 
Add_W_30	movlw	0x30
Hex_cont	addwf	Hex_Bfr,W	; The correct ASCII code for this char !!
	 	return
;
;*******************************************************************
;* SendCmd - Sends command to LCD                                  *
;* This routine splits the command into the upper and lower        * 
;* nibbles and sends them to the LCD, upper nibble first.          *
;*******************************************************************
SendCmd
		banksel	Byte
		movwf	Byte		; Save WREG in Byte variable
		call	Delay_1MS
		swapf	Byte,W		; Send upper nibble first
		andlw	0x0f
		movwf	LCD_DATA
		bcf	LCD_CNTL,RS	; Clear for command
		bsf	LCD_CNTL,E	; Clock nibble into LCD
		bcf	LCD_CNTL,E
		movf	Byte,W		; Write lower nibble last
Send_4bit	andlw	0x0f
		movwf	LCD_DATA
		bcf	LCD_CNTL,RS	; Clear for command
		bsf	LCD_CNTL,E	; Clock nibble into LCD
		bcf	LCD_CNTL,E
		return
;
;*******************************************************************
;* clrLCD - Clear the contents of the LCD                          *
;*******************************************************************
clrLCD
		movlw	CLR_DISP	; Send the command to clear display
		call	SendCmd
		return
;
;*******************************************************************
;* L1homeLCD - Moves the cursor to home position on Line 1         *
;*******************************************************************
L1homeLCD
		movlw	DD_RAM_ADDR|0x00 ; Send command to move cursor to 
		call	SendCmd		 ; home position on line 1
		return

;*******************************************************************
;* L2homeLCD - Moves the cursor to home position on Line 2         *
;*******************************************************************
L2homeLCD
		movlw	DD_RAM_ADDR|0x28 ; Send command to move cursor to
		call	SendCmd		 ; home position on line 2
		return


;*******************************************************************
;* Delay - Generic LCD delay  (1.024mS @ 4MHz)                     *
;* Since the microcontroller can not read the busy flag of the     *
;* LCD, a specific delay needs to be executed between writes to    *
;* the LCD.                                                        *
;*******************************************************************
Delay_1MS				; 2 cycles for call
		clrf	Count		; 1 cycle to clear counter variable
Dloop
		nop
		decfsz	Count,F		; These two instructions provide a
		goto	Dloop		; (256 * 3) -1 cycle count
		return			; 2 cycles for return
;
;*******************************************************************
;*       Delay - 1mS base delay 				   *
;*       input : W Reg.                                            *
;*                                                                 *
;*******************************************************************
Delay_MS
		movwf	Count1
;
DLop1		call	Delay_1MS
		decfsz	Count1,F
		goto	DLop1
		return
;
		END