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LCD problem

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manba

manba

New Member
hi, all....

i used one of Nigel LCD programs to program 2x16 LCD by pic16f877a , but nothing is displyed. :confused::confused::confused:

Code: 
list		p=16f877a	; list directive to define processor
include	<p16f877a.inc>	; processor specific variable definitions
ERRORLEVEL 0,-302
__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _XT_OSC & _WRT_OFF & _LVP_ON & _CPD_OFF
;***** VARIABLE DEFINITIONS
cblock	0x20			;start of general purpose registers
			count			;used in looping routines
			count1			;used in delay routine
			counta			;used in delay routine
			countb			;used in delay routine
			tmp1			;temporary storage
			tmp2
			templcd			;temp store for 4 bit mode
			templcd2	
		endc

LCD_PORT	Equ	PORTB
LCD_TRIS	Equ	TRISB
LCD_RS		Equ	0x04			;LCD handshake lines
LCD_RW		Equ	0x06
LCD_E		Equ	0x07

	
		ORG 0X0005

Initialise	clrf	count
		clrf	PORTA
		clrf	PORTB



SetPorts	bsf 	STATUS,		RP0	;select bank 1
		movlw	0x00			;make all pins outputs
		movwf	LCD_TRIS
		bcf 	STATUS,		RP0	;select bank 0

		call	Delay100		;wait for LCD to settle


		call	LCD_Init		;setup LCD


		clrf	count			;set counter register to zero
Message		movf	count, w		;put counter value in W
		call	Text			;get a character from the text table
		xorlw	0x00			;is it a zero?
		btfsc	STATUS, Z
		goto	NextMessage
		call	LCD_Char
		call	Delay255
		incf	count, f
		goto	Message

NextMessage	call	LCD_Line2		;move to 2nd row, first column

		clrf	count			;set counter register to zero
Message2	movf	count, w		;put counter value in W
		call	Text2			;get a character from the text table
		xorlw	0x00			;is it a zero?
		btfsc	STATUS, Z
		goto	EndMessage
		call	LCD_Char
		incf	count, f
		goto	Message2

EndMessage	
		
Stop		goto	Stop			;endless loop




;Subroutines and text tables

;LCD routines

;Initialise LCD
LCD_Init	movlw	0x20			;Set 4 bit mode
		call	LCD_Cmd

		movlw	0x28			;Set display shift
		call	LCD_Cmd

		movlw	0x06			;Set display character mode
		call	LCD_Cmd

		movlw	0x0d			;Set display on/off and cursor command
		call	LCD_Cmd

		call	LCD_Clr			;clear display
		
		retlw	0x00

; command set routine
LCD_Cmd		movwf	templcd
		swapf	templcd,	w	;send upper nibble
		andlw	0x0f			;clear upper 4 bits of W
		movwf	LCD_PORT
		bcf	LCD_PORT, LCD_RS	;RS line to 0
		call	Pulse_e			;Pulse the E line high

		movf	templcd,	w	;send lower nibble
		andlw	0x0f			;clear upper 4 bits of W
		movwf	LCD_PORT
		bcf	LCD_PORT, LCD_RS	;RS line to 0
		call	Pulse_e			;Pulse the E line high
		call 	Delay5
		retlw	0x00

LCD_Char	movwf	templcd
		swapf	templcd,	w	;send upper nibble
		andlw	0x0f			;clear upper 4 bits of W
		movwf	LCD_PORT
		bsf	LCD_PORT, LCD_RS	;RS line to 1
		call	Pulse_e			;Pulse the E line high

		movf	templcd,	w	;send lower nibble
		andlw	0x0f			;clear upper 4 bits of W
		movwf	LCD_PORT
		bsf	LCD_PORT, LCD_RS	;RS line to 1
		call	Pulse_e			;Pulse the E line high
		call 	Delay5
		retlw	0x00

LCD_Line1	movlw	0x80			;move to 1st row, first column
		call	LCD_Cmd
		retlw	0x00

LCD_Line2	movlw	0xc0			;move to 2nd row, first column
		call	LCD_Cmd
		retlw	0x00

LCD_Line1W	addlw	0x80			;move to 1st row, column W
		call	LCD_Cmd
		retlw	0x00

LCD_Line2W	addlw	0xc0			;move to 2nd row, column W
		call	LCD_Cmd
		retlw	0x00

LCD_CurOn	movlw	0x0d			;Set display on/off and cursor command
		call	LCD_Cmd
		retlw	0x00

LCD_CurOff	movlw	0x0c			;Set display on/off and cursor command
		call	LCD_Cmd
		retlw	0x00

LCD_Clr		movlw	0x01			;Clear display
		call	LCD_Cmd
		retlw	0x00

Delay255	movlw	0xff		;delay 255 mS
		goto	d0
Delay100	movlw	d'100'		;delay 100mS
		goto	d0
Delay50		movlw	d'50'		;delay 50mS
		goto	d0
Delay20		movlw	d'20'		;delay 20mS
		goto	d0
Delay5		movlw	0x05		;delay 5.000 ms (4 MHz clock)
d0		movwf	count1
d1		movlw	0xC7			;delay 1mS
		movwf	counta
		movlw	0x01
		movwf	countb
Delay_0
		decfsz	counta, f
		goto	$+2
		decfsz	countb, f
		goto	Delay_0

		decfsz	count1	,f
		goto	d1
		retlw	0x00

Pulse_e		bsf	LCD_PORT, LCD_E
		nop
		NOP
		bcf	LCD_PORT, LCD_E
		retlw	0x00

;end of LCD routines


Text		addwf	PCL, f
		retlw	'H'
		retlw	'e'
		retlw	'l'
		retlw	'l'
		retlw	'o'
		retlw	0x00

Text2		ADDWF   PCL, f
            	RETLW   'R'
            	RETLW   'e'
            	RETLW   'a'
            	RETLW   'd'
            	RETLW   'y'
            	RETLW   '.'
            	RETLW   '.'
            	RETLW   '.'
            	RETLW   0x00


		end
 

Attachments

  • LCD.JPG
    LCD.JPG
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Are you only testing in Proteus or have you tried it on a real board?
 
hi,

i'm testing the LCD on proteus , if it's ok i'll tried it in real board.....
 
Nigel Goodwin said:
Well you've got no clock oscillator, so it can't work.
Click to expand...

Do you need one in Proteus? I've only ever tried the demo and you set the frequency in the properties (even if the chip doesn't have an internal oscillator).

Not sure if you need one for the simulation though.
 
Two things:

1) Nigel's code definitely works

2) I tried Proteus, a limited version came with a PIC book I bought. I found I spent ages trying to get circuits to work only to find it was some obscure simulation property that was wrong. In the end I gave up and now I breadboard things or use the Oshonsoft simulator.

I suggest trying it on a breadboard and chucking Proteus until you're working with huge circuits that need to operate within very specific limits, which is what a professional simulator like that is good for.
 
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