4-bit Initialization

Initialization of LCD is completed only after the reset sequence and basic initialization commands. We have already discussed about the reset sequence of the lcd in the previous section. So lets look at the programming now...

Assembly Program
;In this whole 4-bit tutorial LCD is connected to
;my controller in following way...
;D4 - P3.0
;D5 - P3.1
;D6 - P3.2
;D7 - P3.3
;EN - P3.7
;RS - P3.5

	lcd_port equ P3         ;LCD connected to Port3
	en equ P3.7             ;Enable connected to P3.7
	rs equ P3.5             ;Register select to P3.5
	
lcd_reset:                  ;LCD reset sequence
	mov lcd_port, #0FFH
	mov delay,#20           ;20mS delay
	acall delayms
	mov lcd_port, #83H      ;Data = 30H, EN = 1, First Init
	mov lcd_port, #03H      ;Data = 30H, EN = 0
	mov delay,#15           ;Delay 15mS
	acall delayms
	mov lcd_port, #83H      ;Second Init, Data = 30H, EN = 1

	mov lcd_port, #03H      ;Data = 30H, EN = 0
	mov delay,#5            ;Delay 5mS
	acall delayms
	mov lcd_port, #83H      ;Third Init

	mov lcd_port, #03H
	mov delay,#5            ;Delay 5mS
	acall delayms
	mov lcd_port, #82H      ;Select Data width (20H for 4bit)

	mov lcd_port, #02H      ;Data = 20H, EN = 0
	mov delay,#5            ;Delay 5mS
	acall delayms
	ret


lcd_init:
	acall lcd_reset         ;Call LCD Reset sequence
	mov a,#28H              ;4-bit, 2 line, 5x7 dots

	acall lcd_cmd           ;Call LCD command
	mov a,#0CH              ;Display ON cursor OFF
	acall lcd_cmd           ;Call LCD command
	mov a,#06H              ;Set entry mode (Auto increment)

	acall lcd_cmd           ;Call LCD command
	mov a,#80H              ;Bring cursor to line 1
	acall lcd_cmd           ;Call LCD command
	ret

C Program
//The pins used are same as explained earlier
#define lcd_port    P3

//LCD Registers addresses
#define LCD_EN      0x80
#define LCD_RS      0x20

void lcd_reset()
{
	lcd_port = 0xFF;
	delayms(20);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(10);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(1);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	delayms(1);
	lcd_port = 0x02+LCD_EN;
	lcd_port = 0x02;
	delayms(1);
}

void lcd_init ()
{
	lcd_reset();         // Call LCD reset
	lcd_cmd(0x28);       // 4-bit mode - 2 line - 5x7 font. 
	lcd_cmd(0x0C);       // Display no cursor - no blink.
	lcd_cmd(0x06);       // Automatic Increment - No Display shift.
	lcd_cmd(0x80);       // Address DDRAM with 0 offset 80h.
 }

Sending Dommand/Data to LCD in 4-bit mode

Assembly Program
lcd_cmd:                  ;LCD command Routine
	mov temp,a            ;Save a copy of command to temp
	swap a                ;Swap to use higher nibble
	anl a,#0FH            ;Mask the first four bits
	add a,#80H            ;Enable = 1, RS = 0
	mov lcd_port,a        ;Move it to lcd port
	anl a,#0FH            ;Enable = 0, RS = 0
	mov lcd_port,a        ;Move to lcd port

	mov a,temp            ;Reload the command from temp
	anl a,#0FH            ;Mask first four bits
	add a,#80H            ;Enable = 1
	mov lcd_port,a        ;Move to port
	anl a,#0FH            ;Enable = 0
	mov lcd_port,a        ;Move to lcd port

	mov delay,#1          ;delay 1 ms
	acall delayms
	ret

lcd_dat:                  ;LCD data Routine
	mov temp,a            ;Keep copy of data in temp
	swap a                ;We need higher nibble
	anl a,#0FH            ;Mask first four bits
	add a,#0A0H           ;Enable = 1, RS = 1
	mov lcd_port,a        ;Move to lcd port
	nop
	clr en                ;Enable = 0

	mov a,temp            ;Reload the data from temp
	anl a,#0FH            ;we need lower nibble now
	add a,#0A0H           ;Enable = 1, RS = 1
	mov lcd_port,a        ;Move to lcd port
	nop
	clr en                ;Enable = 0

	mov delay,#1          ;Delay 1mS
	acall delayms
	ret

C Program
void lcd_cmd (char cmd)
{ 
	lcd_port = ((cmd >
>
 4) & 0x0F)|LCD_EN;
	lcd_port = ((cmd >
>
 4) & 0x0F);

	lcd_port = (cmd & 0x0F)|LCD_EN;
	lcd_port = (cmd & 0x0F);

	delayus(200);
	delayus(200);
}

void lcd_data (unsigned char dat)
{ 
	lcd_port = (((dat >
>
 4) & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = (((dat >
>
 4) & 0x0F)|LCD_RS);
	
	lcd_port = ((dat & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = ((dat & 0x0F)|LCD_RS);

	delayus(200);
	delayus(200);
}

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Conversation

Sat Aug 01 2015, 05:57 AM
ghulamqadir
i want to communitcate wifi module with android phone using pic18f4550. Any Suggestion????????
Sat Aug 01 2015, 05:56 AM
ghulamqadir
Slam
ExperimenterUK
Thu Jul 30 2015, 11:41 PM
@Muhammad Aarshad build what ?
Wed Jul 29 2015, 06:42 PM
Muhammad Aarshad
Hello I want to build it, but I don't know how can I program the micro controller. Can You send me the code of the IC? Thanks in advance My e-mail: [email protected]
Sat Jul 25 2015, 10:37 PM
Arnali
What does the cross means? The ones from pin 7,8,9,10 of the LCD?
Fri Jul 24 2015, 09:53 AM
HARSHAL PATIL
....
shyam
Thu Jul 23 2015, 01:42 PM
hi Ajay
ajay_bhargav
Mon Jul 20 2015, 04:38 AM
@Rohit Biradar, I am glad my tutorial helped
Thu Jul 16 2015, 06:19 PM
Rohit Biradar
Thanks a lot publisher of this tutorial. Everybody tells about the nibble sending methods and the command set for 4-wire lcd interface. You are the first to tell me about the most important part that is resetting the lcd. This thing got me all day. Now I can sleep in peace. Thanks once again. Million thanks.
Thu Jul 16 2015, 12:24 PM
Baby
my project is related to control the door in dam. by keil program how can i control the same.

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albatain
Fri Jul 31 2015, 02:58 AM
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Tanvir.
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balvant
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Mc_Comet32 Avatar
Posted By Mc_Comet32
Sun Jul 26 2015, 05:49 PM
ExperimenterUK Avatar
Posted By ExperimenterUK
Thu Jul 23 2015, 08:14 PM
Try this link.Basically find the tacho output pin...
seoulmak Avatar
Posted By seoulmak
Mon Jul 20 2015, 03:44 PM
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Posted By ajay_bhargav
Mon Jul 20 2015, 04:42 AM
Ok then, check if you did not mention "LCD_ClearSc...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Jul 20 2015, 04:41 AM
I am assuming you're talking about the small CPU f...
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Posted By Amit Kumar Das
Sun Jul 19 2015, 04:17 AM
Yes they are fine. I have included everything. Una...
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Posted By seoulmak
Fri Jul 17 2015, 08:41 AM
yes, but i need more information to connect the f...
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Posted By ExperimenterUK
Wed Jul 15 2015, 05:42 PM
Is this a project listed on this site ?