Code:
+;********************************************************************** ; Simple routines for controlling a HD44780 display * ; Useful if you are adding a display to an old project. * ; The data bus and control lines can use any pin. * ; If the pin is open collector you need a pull up resistor * ; * ;********************************************************************** ; * ; Filename: lcd.asm * ; Date: 20080204 * ; File Version: 1.1 * ; * ; Author: Stefan Johansson * ; tessier at telia dot com * ; * ;********************************************************************** ; * ; Usage: #include <lcd.asm> * ; call LCDINIT ; Initialize LCD * ; * ; movlw 0x05 * ; call LCDADD ; Goto lcd adress 0x05* ; * ; movlw 'A' * ; call LCDSEND ; Write character A * ;********************************************************************** ; * ; Variables: D0 * ; D1 * ; D2 * ; LCDTmp * ; * ;********************************************************************** ; * ; Notes: This was written and compiled for PIC 16f677. * ; Modification might be needed for other models. * ; Any comments, questions or improvements... mail me * ; * ;********************************************************************** ; LCD control lines ; Modify to match your project #define LCD_D4 PORTB, 3 #define LCD_D5 PORTB, 2 ; 4 data lines #define LCD_D6 PORTB, 1 #define LCD_D7 PORTB, 0 #define LCD_RS PORTB, 5 ; 0 = Command, 1 = Data #define LCD_E PORTB, 4 ; 1 to send data ;************************************************************* ; Initialize LCD functions ;************************************************************* LCDINIT ; Set correct TRIS values for LCD ports bsf STATUS, RP0 ;Bank 1 bcf LCD_RS bcf LCD_E bcf LCD_D4 bcf LCD_D5 bcf LCD_D6 bcf LCD_D7 bcf STATUS, RP0 ;Bank 0 movlw 0x40 ; Initial delay, probably not needed... call delay ; Forced LCD initialization bcf LCD_RS ; Set command mode bcf LCD_E bsf LCD_D4 bsf LCD_D5 bcf LCD_D6 bcf LCD_D7 call PULSE movlw 0x04 call delay call PULSE call short_dly call short_dly call PULSE ; Send the command to select 4-bit mode first bcf LCD_D4 call PULSE ; Function set ; Format: xxxDNFxx D: 1= 8-bit, 0= 4-bit (use 4-bit!) movlw b'00101000' ; N: 1= 2 lines, 0= 1 line call LCDSEND ; F: 1= 5x10 font, 0= 5x8 font ; Display control ; Format: xxxxxDCB D: Display on(1)/0ff(0) movlw b'00001100' ; C: Cursor on(1)/0ff(0) call LCDSEND ; B: Blink on(1)/0ff(0) ; Entry mode set ; Format: xxxxxxIS I: 1= Increment counter, 0= Decrement counter movlw b'00000110' ; S: 1= "Accompanies display shift" call LCDSEND ; Cursor or display shift ; Format: xxxxSRxx S: 1= Display shift, 0= Cursor move movlw b'00010000' ; R: 1= Shift right, 0= Shift left call LCDSEND movlw b'00000001' ; Clear screen call LCDSEND bsf LCD_RS ; Set data mode RETURN ;************************************************************* ; Moves "cursor" ;************************************************************* LCDADD bcf LCD_RS ; Command mode iorlw 0x80 ; Goto DDRAM adress call LCDSEND bsf LCD_RS ; Data mode call delay_1ms ; Takes a couple of ms RETURN ;************************************************************* ; Sends contens of W to display ;************************************************************* LCDSEND ; Sends character in W to lcd. Does not alter RS line! movwf LCDTmp bcf LCD_D4 bcf LCD_D5 bcf LCD_D6 bcf LCD_D7 btfsc LCDTmp, 7 bsf LCD_D7 btfsc LCDTmp, 6 bsf LCD_D6 btfsc LCDTmp, 5 bsf LCD_D5 btfsc LCDTmp, 4 bsf LCD_D4 call PULSE bcf LCD_D4 bcf LCD_D5 bcf LCD_D6 bcf LCD_D7 btfsc LCDTmp, 3 bsf LCD_D7 btfsc LCDTmp, 2 bsf LCD_D6 btfsc LCDTmp, 1 bsf LCD_D5 btfsc LCDTmp, 0 bsf LCD_D4 call PULSE return ;************************************************************* ; Pulse enable line ;************************************************************* PULSE ; Pulse Enable. bsf LCD_E nop ; Increase the delay here if you get nop ; problems with high clock speed nop ; Probably not needed since nop ; 1 instruction @10MHz = 400ns bcf LCD_E call delay_1ms call delay_1ms return ;************************************************************* ; Clears display ;************************************************************* LCDCLR ; clears the entire display bcf LCD_RS ; Set command mode movlw b'00000001' ; Clear screen call LCDSEND bsf LCD_RS ; Set data mode return ;************************************************************* ; Calls the delay_1ms W times ;************************************************************* delay movwf d0 dly_loop call delay_1ms decfsz d0, F goto dly_loop return ;************************************************************* ; 1ms delay. ; Modify this to match your processor speed. ; http://www.piclist.org/techref/piclist/codegen/delay.htm ;************************************************************* delay_1ms movlw 0xF3 ;2498 cycles movwf d1 movlw 0x02 movwf d2 Delay_0 decfsz d1, f goto $+2 decfsz d2, f goto Delay_0 goto $+1 ;2 cycles return ;4 cycles (including call) ;************************************************************* ; 40us delay. ; Modify this to match your processor speed. ; http://www.piclist.org/techref/piclist/codegen/delay.htm ;************************************************************* short_dly movlw 0x1F ;94 cycles movwf d1 short_dly_0 decfsz d1, f goto short_dly_0 goto $+1 ;2 cycles return ;4 cycles (including call)
Comments:
Stefan Johansson replies: But it works for me... Anyone else?+
| file: /techref/io/lcd/lcd.asm.htm, 8KB, , updated: 2008/2/4 13:59, local time: 2008/12/2 22:50,
owner: SJ-telia-G32,
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| ©2008 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions? Please DO link to this page! Digg it! <A HREF="http://www.sxlist.com/techref/io/lcd/lcd.asm.htm"> Simple routines for controlling a HD44780 display. Useful if you are adding a display to an old project. The data bus and control lines can use any pin. It works just fine on pic 16f677 and 16f877.</A> |
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