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

Thu Jan 29 2015, 11:24 AM
durai
I found discussion relevant to my problem (link:http://www.8051projects.net/t59199/gsm-cdma-discussion/flashing-new-firmware-in-sim900-modem.htm) but i could not find the project mentioned in that discusion
Thu Jan 29 2015, 11:21 AM
durai
Hi i am using a SIM/900A GSM modem, I want to send email with an attachement using a microcontroller but when i try to use AT_Email commands it gives me error,I think modem doesnot support those commands,is there any other way to send mail using that modem??
ajay_bhargav
Thu Jan 29 2015, 06:54 AM
@gaurav, please mail me message you're trying to post.
ExperimenterUK
Thu Jan 29 2015, 01:17 AM
bhagyesh.bhavasar/gaurav.k I can post with Firefox. Can you try other browsers ?
naqirizvi
Wed Jan 28 2015, 08:08 AM
the web theme is too much buggy and heavy , admin please change it to simple theme, so that user can browse quickly
naqirizvi
Wed Jan 28 2015, 08:07 AM
some one please share software name or ebooks related to avr
bhagyesh.bhavasar
Tue Jan 27 2015, 11:06 AM
i want to share my project but there is problem occurred during postng
bhagyesh.bhavasar
Tue Jan 27 2015, 05:58 AM
@ExperimentalUK i have used that purple button but same as previous it takes me to blank page
ExperimenterUK
Sun Jan 25 2015, 08:10 PM
This box is for chat. Post problems in a suitable forum
ExperimenterUK
Sun Jan 25 2015, 08:04 PM
@gaurav.k Use the purple "Post reply" button. Green buttons often present a fresh edit box.

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dear sir, please tell me how to do t...
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T he P89V51RD2 P1.5, P1.6, P1.7 has extra curren...
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Circuit diagram i am following i am not sure is it...
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hello sir, plz tell me the circuit diagram interfa...
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Moreover I see the segment Anode is connected via ...
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LCD tutorial is written for 8051, you need to chan...