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

ExperimenterUK
Sun Mar 01 2015, 07:06 AM
@Anupam Biswas..post all you have done in the GSM forum
Sat Feb 28 2015, 02:51 PM
Anupam Biswas
I am doinga project on gsm based home automation.I have done alittle study about at commands.I am using Atmel 89c51 with yhe gsm module.I am unable to receive any message via the module.The simulation is done on proteus and i am using a virtual terminal.Can anyone please help me?Thanks in advance.
Tue Feb 24 2015, 12:47 AM
MrCurious
is Stat a global variable too? you reference it in Chan's "disk_status" function.
Sat Feb 21 2015, 09:10 PM
Harikumar
കൊള്ളാം
ExperimenterUK
Fri Feb 20 2015, 06:28 AM
@sugikz.. I have asked Ajay about it, he'll soon sort it out
Thu Feb 19 2015, 12:22 PM
sugikz
"Sorry no bots allowed! You entered two different email addresses. Please enter a valid email address in the two fields provided"
Thu Feb 19 2015, 12:21 PM
sugikz
this are the problem notice box;
Thu Feb 19 2015, 12:20 PM
sugikz
yes, i still got stuck on email problem, i've used gmail, yahoo, and told some friends of mine to sign up on the site, but they face the same problem as iam,
Thu Feb 19 2015, 05:48 AM
sjeeva
hi, is any doing a project on raspberry pi
Thu Feb 19 2015, 05:48 AM
sjeeva
hi

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raamchandran
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ABiDAEV Avatar
Posted By ABiDAEV
Sun Mar 01 2015, 11:42 AM
Thanks for sharing, but can you please update the ...
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Posted By sankalp_s
Thu Feb 26 2015, 09:27 PM
What are you trying to make ?ExperimenterUKsir i w...
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Posted By ExperimenterUK
Thu Feb 26 2015, 12:58 AM
We seem to be moving away from the original projec...
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Posted By ajay_bhargav
Wed Feb 25 2015, 02:02 PM
You will need a 64 bytes buffer that will be writt...
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Posted By PsySc0rpi0n
Wed Feb 25 2015, 09:24 AM
I've already read that tutorial and almost all oth...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Feb 25 2015, 04:56 AM
brightness control is going to be tough job as you...
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Posted By ajay_bhargav
Wed Feb 25 2015, 04:36 AM
I've already read that tutorial and almost all oth...
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Posted By sankalp_s
Tue Feb 24 2015, 07:18 PM
The attached code is for up to 16 LEDs.Just point ...
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Posted By sankalp_s
Tue Feb 24 2015, 07:12 PM