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LCD HD47780 interfacing

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weijie

Wed Jul 09 2008, 07:25PM

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i was trying to interface my at89c51ed2 with a LCD
however , i got some problem initialize it ..
there is a post on www.bipom.com teaching ppl
but i don understand why we nid to put 0x30 into data for 3 times before we can put in other command . can someone explain to me ?
anyone got simple c code for lcd ?
Thank you ~

say2paul

Wed Jul 09 2008, 09:17PM

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Go through this link:

http://www.8051projects.net/lcd-interfacing/

It will explain you each n everything about interfacing LCD with 8051.

Colin Mac

Thu Jul 10 2008, 06:53AM

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http://www.edsim51.com/examples.html#prog4

see this too

weijie

Thu Jul 10 2008, 07:09AM

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http://www.8051projects.net/lcd-interfacing/initialization.php
this page shows that we nid input a 30H as command into it before any other command . Why ?

Ajay

Thu Jul 10 2008, 08:13AM

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30H is the init byte for LCD.

As i explained there are two types of resets in LCD
1. Power on reset
2. Software reset

1. Power on reset, as name says. LCD get reset during power up by itself (thats the reason you see blocks on LCD when you just power it up). During power on reset LCD get initialized in 8-bit mode.

2. Software reset, This kind of reset is to reset LCD with software instructions. 30H is sent 3 times as init byte sequence.

As you know during power on reset LCD initialized in 8-bit mode so no need to give software reset if you are using LCD in 8-bit mode, but if you want to use LCD in 4-bit mode then you have to give LCD a software reset and tell the LCD that you are going to use 4-bit mode.
reset sequence is explained in 4-bit initialization section. Please read it carefully.

www.rickeyworld.info
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weijie

Sat Jul 12 2008, 10:58AM

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i had completed the c code for lcd . but i cant run it on my at89c51ed2 .
i choose to put 8 data lines at port 0 , and RS,RW,EN at port 2 .
do i nid to put a Vcc (5V) , through a resistor to those pins at port 2 ?
should i configure such like http://www.edsim51.com/examples.html using resistor value 10k ?

#include <at89c51ed2.h>

#define LCD_DATA P0
#define LCD_EN P2_0
#define LCD_RW P2_1
#define LCD_RS P2_2

void delay(int);
void WRT_COMM();
void WRT_DATA();

void main()
{
delay(18000);

LCD_DATA = 0x38; //Initialize LCD 2 Lines, 5 x 7 Matrix, 8 bit interface.
WRT_COMM();

LCD_DATA = 0x0E; //Display ON, Cursor ON,blink off
WRT_COMM();

LCD_DATA = 0x01; //Clear Display
WRT_COMM();
delay(18000);

LCD_DATA = 0x06; //Increment cursor position, No display shift.
WRT_COMM();

LCD_DATA = 'D';
WRT_DATA();

LCD_DATA = 'O';
WRT_DATA();

LCD_DATA = 'N';
WRT_DATA();

LCD_DATA = 'E';
WRT_DATA();
}

void delay(int time)
{
int t;
time = time * 2; //each machine cycle is 0.5u second
for(t=1; t<=time; t++)
{}
}

void WRT_COMM()
{
LCD_RS = 0;
LCD_RW = 0;
LCD_EN = 1;
LCD_EN = 0;
delay(180);
}

void WRT_DATA()
{
LCD_RS = 1;
LCD_RW = 0;
LCD_EN = 1;
LCD_EN = 0;
delay(180);
}

[ Edited Sat Jul 12 2008, 07:39PM ]

Arun Kumar V

Sat Jul 12 2008, 11:45PM

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Hi friend,

Avoid using Port 0 and port 2 , instead use P1 for 8 bit data and P3 for control lines of LCD.

if you insist on using P0 then you need to have 10K pull up resistors, also try adjusting the Contrast on the LCD, i hope you have a 10K pot between Vss, Vdd, and Vee of LCD

Arun

[ Edited Sat Jul 12 2008, 11:46PM ]

weijie

Sat Jul 12 2008, 11:49PM

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but the controller that i using is at89c51ed2 pid40 .
it have special function on port 1 and 3 that i need to use it for other purpose later

Arun Kumar V

Sat Jul 12 2008, 11:56PM

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the answer is in my last post

if you insist on using P0 then you need to have 10K pull up resistors,

Arun

sashijoseph

Sun Jul 13 2008, 12:56AM

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Posts: 648
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@weijie

In your code try increasing the delay in the range of milliseconds.
sth like this.....

void delay(int time)
{
int t,i;
time = time * 2; //each machine cycle is 0.5u second
for(t=1; t<=time; t++)
for( i=0 ; i<750 ; i++) ;
}

Also insert a small (1 ms) delay between LCD_EN 1 and 0.

It would be better to use the 'busy-flag' method rather than fiddling with delay values.

Let there be music........