3-Draht Interface für Standard LCD-Module

Diese Schaltung ist ein einfaches 3-Draht Interface für Standard HD44780 und kompatible LCD-Text-Module.
Die Codebeipiele enthalten nur die Teile, die direkt das Display ansteuern.
Komplette Codebeispiele folgen ...
Anstelle des HCT164 kann auch ein LS164 genommen werden.

Schaltplan des Interface

Quellcode für Microchip PIC Controller.

; Microchip PIC @ 4MHz
;------------------------------------------------------------------------
;Variblen		
  LCD_SERDATA		; Serielle Daten LCD	
  LCD_BITCNT    ; Bitcounter LCD
  LCD_RS        ; RS Flag  bit 0
;------------------------------------------------------------------------
; LCD pins
#define	  LCD_DATA   PORTB,1
#define	  LCD_CLK	   PORTB,2
#define	  LCD_ENABLE PORTB,3
;------------------------------------------------------------------------
;
; 8 Bit ans LCD plus ENABLE & RS
;
LCD_SER_SEND
        movwf LCD_SERDATA	
        bcf   LCD_ENABLE	
        bcf   LCD_DATA	
        movlw 0x08	
        movwf LCD_BITCNT
slcd1   btfsc LCD_SERDATA,7  	 ; highbit data
        bsf   LCD_DATA  
        bsf   LCD_CLK          ; clock impuls
        bcf   LCD_CLK
        bcf  	LCD_DATA
        rlf	  LCD_SERDATA,f    ; daten links rotieren
        decfsz LCD_BITCNT,f    ; 8 bit fertig ?
        goto  slcd
        btfsc LCD_RS,0
        bsf   LCD_DATA         ;rs high
        nop
        bs    LCD_ENABLE
        nop
        bcf   LCD_ENABLE
        return

Quellcode für Atmel AVR Controller.

; AVR @ 4MHz
.equ	lcd_e		= 0
.equ	lcd_cl		= 1
.equ	lcd_da_rs	= 2
.equ	lcd_port	= PORTC
.equ	lcd_pddr	= DDRC
.def	loop_cnt_1	= r19		; loop counter
.def 	loop_cnt_2	= r20		; help
.def	lcd_data 	= r22		; daten für lcddisplay

;-------------------------------------------------
;***************************************************************************
;*
;*	func:	lcd_out_c
;*		lcd_out_d
;*
;*	vars:	lcd_data
;*		loop_cnt_1
;*		
;*	subs:	wait_x_100u
;*
;***************************************************************************
lcd_out_c:
        push	loop_cnt_1
        delay_x_100u 2
        rcall	lcd_out8
        cbi	lcd_port,lcd_da_rs
        rjmp	lcd_en
lcd_out_d:
        push	loop_cnt_1
        delay_x_100u 2
        rcall	lcd_out8
        sbi	lcd_port,lcd_da_rs
        rjmp	lcd_en
lcd_en:
        sbi	lcd_port,lcd_e
        pop	loop_cnt_1
        cbi	lcd_port,lcd_e
        ret

lcd_out8:
        ldi	loop_cnt_1,8
rorloop: rol	lcd_data
        brcs	eout
        cbi	lcd_port,lcd_da_rs		
        rjmp	edo
eout:   sbi	lcd_port,lcd_da_rs
edo:    sbi	lcd_port,lcd_cl
        cbi	lcd_port,lcd_cl
        dec	loop_cnt_1
        brne	rorloop
        ret

;***************************************************************************
;*
;*	func:	wait_x_100u
;*
;*	vars:	loop_cnt_1
;*		loop_cnt_2
;*
;***************************************************************************
wait_x_100u:
        push	loop_cnt_2
        mov	loop_cnt_2,loop_cnt_1
l2loop: ldi 	loop_cnt_1,199			; 99
lcloop: dec	loop_cnt_1
        or	loop_cnt_1,loop_cnt_1
        brne	lcloop
        dec	loop_cnt_2
        or	loop_cnt_2,loop_cnt_2
        brne	l2loop
        pop	loop_cnt_2
        ret