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Salim C. Andraos
03/27/12 11:40
Read: 1315 times


 
#186911 - Tutorial/Book question about 8052/LCD



EN equ P3.3	
RW equ P3.4	
RS equ P3.5	
DAT equ P1	
	
wait_lcd:	
 clr RS			;command
 setb RW		;read command
 setb EN		;start lcd command
 mov P1, #0FFh	
 mov A, P1	
 jb ACC.7, wait_lcd	;if bit 7 high, lcd still busy
 clr EN			;finish command
 clr RW			;turf off RW for future commands
 ret	
	
lcd_command:	
 clr RS			;low to indicate command
 clr RW			;low to indicate write
 mov DAT, A	
 setb EN		;high to initiate command
	
 mov R0, #30h	
 loop:			;loops 48 times instead of 4
  nop			; to compensate for the Dallas' speed
  djnz R0, loop	
	
 clr EN	
 lcall wait_lcd		;wait for command to execute
 ret	
	
init_lcd:	
 mov A, #38h		;8-bit data bus, 5x8 font
 lcall lcd_command	
 mov A, #0Eh		;turn on lcd, turn on cursor
 lcall lcd_command	
 mov A, #06h		;turn on cursor auto advance
 lcall lcd_command	
 ret	
	
clear_lcd:	
 mov A, #01h	
 lcall lcd_command	
 ret	
	
write_lcd_text:	
 setb RS		;RS high to indicate text
 clr RW			;RW low to indiacte write
 mov DAT, A	
 setb EN		;high to initiate command
	
 mov R0, #30h	
 loop2:			;loops 48 times instead of 4
  nop			; to compensate for the Dallas' speed
  djnz R0, loop2	
	
 clr EN	
 lcall wait_lcd		;wait for command to execute
 ret	
	
lcall init_lcd		;initialize lcd
lcall clear_lcd		;clear screen
	
mov A, #'H'		;send text data to lcd
lcall write_lcd_text	
mov A, #'e'	
lcall write_lcd_text	
mov A, #'l'	
lcall write_lcd_text	
mov A, #'l'	
lcall write_lcd_text	
mov A, #'o'	
lcall write_lcd_text	
	
end	


 


Hook up is per the above schematic. Code is from Craig's book and tutorials on this site.
All I get are first line dark squares and blank screen after adjusting contrast. No text.

Anyone see the problem?

List of 4 messages in thread
TopicAuthorDate
Tutorial/Book question about 8052/LCD      Salim C. Andraos      03/27/12 11:40      
   reset?      Jan Waclawek      03/28/12 00:32      
   Problem solved      Salim C. Andraos      03/28/12 07:32      
      did you      Erik Malund      03/28/12 07:51      

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