LCD Interface with ARM 2138 in 4 bit mode

The various LCD commands used to write data to LCD are given below : -

For Writing to LCD RS, RW and EN pins of a 16character 2 line LCD. It has 8 data pins can be configured in 4 bit and 8bit using proper commands. RS=1 for writing data, and RS=0 for register select for writing special character but for our program it is RS=1.

RW=0 I kept as such as we are writing data. EN=1 for enabling writing for 20 s and then EN=0 disabled.

Steps For LCD Interface With ARM 2138 In 4 Bit Mode

Step 1: initialize the LCD in 4 bit with 2 line.

Step2: create a library for writing a letter or strings.

The library is as follows.

Code For Creating Library For LCD Interface With ARM 2138 In 4 Bit Mode

#include <LPC21xx.h>

void Delay(unsigned long b)

{

    while (--b!=0);

}

void write_command(int cmd)

{

        IO1CLR |= 0x00f00000; // Clear Data pins

        IO1CLR |= 0x00040000; // RW = 0

        IO1CLR |= 0X00020000; // RS= 0,

        IO1SET |= 0x00f00000 & cmd; //Set Data pins

        IO1SET |= 0X00080000; // Enable = 1

        Delay(30000); // Provide Delay

        IO1CLR |= 0x00080000; // Set Enable=0

}

void write_data(int dat)

{

        IO1CLR |= 0x00f00000; // Clear Data pins4-D7

        IO1CLR |= 0x00040000; // RW= 0

        IO1SET |= 0X00020000; //RS= 1

        IO1SET |= 0x00f00000 & dat; // Set Data pins

        IO1SET |= 0X00080000; // Enable = 1

        Delay(30000); //Provide Delay

        IO1CLR |= 0x00080000; //Set Enable=0 

}

void lcd_data(char dat)

{

        write_data(dat << 16);

        write_data(dat << 20);

}

void lcd_command(char cmd)

{

        write_command(cmd << 16);

        write_command(cmd << 20);

}

void printlcd(char *CPtr)

{

        while(*CPtr != 0)

        {

                lcd_data(*CPtr);

                CPtr++;

                Delay(20000);

        }

}

void init_lcd(void)

{

        IO1DIR |= 0x00FE0000;

        Delay(200000) ;

        Delay(100000);

        write_command(0x30 << 16);

        Delay(100000);

        write_command(0x20 << 16);

        lcd_command(0x01); /* clear display */

        lcd_command(0x06); /* auto address inc */

        lcd_command(0x0c); /* cursor off */

        lcd_command(0x28); lcd_command(0x80); /* first location */

}

Then The Main Program For  LCD Interface With ARM 2138 In 4 bit Mode Calling This Header File As Follows To Write A String “Hello World” : -

#include <LPC21xx.h>

#include "lcd.h"

int main(void) 

{

        init_lcd();

        while(1)

        {

                lcd_command(0x01);

                lcd_command(0x80);

                printlcd("Welcome To");

                lcd_command(0xC0);

                printlcd("Hello World");

                Delay(50000000);

        }

}

Circuit Diagram For LCD Interface With ARM 2138 In 4 Bit Mode : -