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);
}

Share it! Like it!

Conversation

ExperimenterUK
Sat Sep 13 2014, 12:34 PM
jaimin1212,Pimpalkhare Create a thread for your question
jaimin1212
Sat Sep 13 2014, 02:35 AM
i want to make self balancing robot using MPU6050 using atmega8.. please help to get data of gyro and accelerometer from this sensor through atmega8.
Thu Sep 11 2014, 09:00 AM
Sunil Pimpalkhare
Hello sir, I am trying to make Wearfin project https://www.youtube.com/watch?v=iZ6PVBvQf-g so can u help me in teaching how to built the program???
Thu Sep 11 2014, 02:21 AM
hariom panday
plz hlp me in my project
iec.naga
Tue Sep 09 2014, 01:19 AM
spi
Mon Sep 08 2014, 08:14 AM
fameem
water changing in fish tank automatically using microcontoller with timer. send idea to me
dexter_a
Sat Sep 06 2014, 11:09 AM
hello guys
Sat Sep 06 2014, 10:10 AM
munaxa
plx guide me
Sat Sep 06 2014, 10:09 AM
munaxa
hi i want to buy plx guie me
ajay_bhargav
Sat Sep 06 2014, 03:10 AM
@Ben, Its hard to undrstand the context like this. If you can post in forum with some example code we might answer you better.

Downloads

Comments

engwas
Tue Sep 30 2014, 08:42 AM
zsachico
Tue Sep 30 2014, 12:18 AM
evergreencare
Sat Sep 27 2014, 03:39 AM
Agnoor
Thu Sep 25 2014, 02:39 AM
fouadzeyad
Tue Sep 23 2014, 05:04 AM
deepbhadani
Fri Sep 19 2014, 01:08 PM
desaiakshay92
Fri Sep 19 2014, 12:45 AM
Fiddu
Thu Sep 18 2014, 02:28 AM

Online

Guests: 38, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 01:37 AM

Members: 37522
Newest member: engwas
Forum Activity
kirangowle Avatar
Posted By kirangowle
Sat Sep 20 2014, 12:35 AM
Hello All,I want to connect normal speaker (as a s...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Sep 17 2014, 12:59 AM
I think its important to list out the features of ...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Sep 17 2014, 12:45 AM
you need to put a wait condition in ISR till the s...
akshar Avatar
Posted By akshar
Mon Sep 15 2014, 04:41 AM
sir,i used microcontroller 89v51rd2 in circuit. No...
bobparihar Avatar
Posted By bobparihar
Mon Sep 15 2014, 02:24 AM
i am programming interrupt 0 using 8051my task is....
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Sep 13 2014, 12:23 PM
There may not be an exact equivalent .You will hav...
akshar Avatar
Posted By akshar
Sat Sep 13 2014, 03:18 AM
Sir, Good Morning,Thank you for making me a member...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Sep 11 2014, 12:52 AM
which compiler are you using? I suggest XC8 with M...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Sep 11 2014, 12:49 AM
I always prefer Olimex Dev boards when it comes to...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Sep 11 2014, 12:44 AM
master will always lower down the Chip select... s...