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 : -
