Microcontroller LCD 4 bits mode - microcontroller

Question

I have been studying microcontrollers so far and I gone through LCD and understood how it worked in 8 bits mode but 1 thing I don't understand is how to work with it in 4 bits mode and whatever I try in code I cant ever make it and I searched almost all the sites available on the internet to explain this topic but still didn't get it so I would very much appreciate if someone could spend some of his time explaining this to me thanks in advance.

Answer 1

#user3674628: By now you must have had known how to interface in 4-bit modes. Though you didnt specify the compiler you use here is an example I have been using with mplabx with xC8 compiler. It works pretty well. Do not forget to adjust the configuration bits on mplabx. Success!
// PIC18F4550 Configuration Bit Settings
// 'C' source line config statements
#include <xc.h>
// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.
// CONFIG1L
#pragma config PLLDIV = 5
#pragma config CPUDIV = OSC1_PLL2
#pragma config USBDIV = 2
// CONFIG1H
#pragma config FOSC = INTOSCIO_EC //this uses internal oscillator
#pragma config FCMEN = OFF
#pragma config IESO = OFF
// CONFIG2L
#pragma config PWRT = OFF
#pragma config BOR = OFF
#pragma config BORV = 3
#pragma config VREGEN = OFF
// CONFIG2H
#pragma config WDT = OFF
#pragma config WDTPS = 32768
// CONFIG3H
#pragma config CCP2MX = ON
#pragma config PBADEN = OFF
#pragma config LPT1OSC = OFF
#pragma config MCLRE = OFF
// CONFIG4L
#pragma config STVREN = ON
#pragma config LVP = OFF
#include <p18f4550.h>
#include <stdio.h>
#include <stdlib.h>
#include <plib/xlcd.h>
/* DATA_PORT defines the port to which the LCD data lines are connected */
#define DATA_PORT PORTB //for 4-bit mode connect D4-D7 of lcd to B0-B3 of lcd
#define TRIS_DATA_PORT TRISB
/* This defines the port where the control lines are connected.
* These are just samples, change to match your application.
* you may omit this part because its in y the compiler.
*/
#define RW_PIN LATBbits.LATB6
#define TRIS_RW TRISBbits.TRISB6
#define RS_PIN LATBbits.LATB5
#define TRIS_RS TRISBbits.TRISB5
#define E_PIN LATBbits.LATB4
#define TRIS_E TRISBbits.TRISB4
#define _XTAL_FREQ 4000000 // SET THIS TO SUIT YOUR FREQUENCY
void Wait(unsigned int delay)//delay for 100ms
{
for(;delay;delay--)
__delay_us(100);
}
//initialise the lcd
void LCDInit(){
OpenXLCD(FOUR_BIT & LINES_5X7 & CURSOR_ON & BLINK_OFF);
while(BusyXLCD());
WriteCmdXLCD(SHIFT_DISP_LEFT);
while(BusyXLCD());
}
void main(void)
{
ADCON1 = 0xF; // No analog, all digital i/o
TRISB = 0x0;
LCDInit()//initialise lcd
putrsXLCD( " Thanks God" );//display on the lcd
while(BusyXLCD());
WriteCmdXLCD(0xC0);// go to the next line on the lcd
while(BusyXLCD());
putrsXLCD( " I made it" );//display on the lcd
while(BusyXLCD());
while(1);
}
void DelayFor18TCY(void){
Delay10TCYx(20);
}
void DelayPORXLCD(void){
Delay1KTCYx(30);
}
void DelayXLCD(void){
Delay1KTCYx(10);
}

Answer 2

Have you tried these?
http://learningmsp430.wordpress.com/2013/11/16/16x2-lcd-interfacing-in-4-bit-mode/
http://www.spickles.org/projects/4-bit-lcd/
The first is pretty informative, and the second has example source code.

Answer 3

For 4-bit interface data, only four bus lines (DB4 to DB7) are used for transfer. Bus lines DB0 to DB3
are disabled. The data transfer between the HD44780U and the MPU is completed after the 4-bit data
has been transferred twice. As for the order of data transfer, the four high order bits (for 8-bit
operation, DB4 to DB7) are transferred before the four low order bits (for 8-bit operation, DB0 to
DB3).
The busy flag must be checked (one instruction) after the 4-bit data has been transferred twice. Two
more 4-bit operations then transfer the busy flag and address counter data.
For 8-bit interface data, all eight bus lines (DB0 to DB7) are used.
Here is an example on how it works:
#include <msp430g2553.h>
#define DR P1OUT = P1OUT | BIT4 // define RS high
#define CWR P1OUT = P1OUT & (~BIT4) // define RS low
#define READ P1OUT = P1OUT | BIT5 // define Read signal R/W = 1 for reading
#define WRITE P1OUT = P1OUT & (~BIT5) // define Write signal R/W = 0 for writing
#define ENABLE_HIGH P1OUT = P1OUT | BIT6 // define Enable high signal
#define ENABLE_LOW P1OUT = P1OUT & (~BIT6) // define Enable Low signal
void data_write(void)
{
ENABLE_HIGH;
delay(2);
ENABLE_LOW;
}
void data_read(void)
{
ENABLE_LOW;
delay(2);
ENABLE_HIGH;
}
void check_busy(void)
{
P1DIR &= ~(BIT3); // make P1.3 as input
while((P1IN&BIT3)==1)
{
data_read();
}
P1DIR |= BIT3; // make P1.3 as output
}
void send_command(unsigned char cmd)
{
check_busy();
WRITE;
CWR;
P1OUT = (P1OUT & 0xF0)|((cmd>>4) & 0x0F); // send higher nibble
data_write(); // give enable trigger
P1OUT = (P1OUT & 0xF0)|(cmd & 0x0F); // send lower nibble
data_write(); // give enable trigger
}
void send_data(unsigned char data)
{
check_busy();
WRITE;
DR;
P1OUT = (P1OUT & 0xF0)|((data>>4) & 0x0F); // send higher nibble
data_write(); // give enable trigger
P1OUT = (P1OUT & 0xF0)|(data & 0x0F); // send lower nibble
data_write(); // give enable trigger
}
void send_string(char s)
{
while(s)
{
send_data(*s);
s++;
}
}
void lcd_init(void)
{
P1DIR |= 0xFF;
P1OUT &= 0x00;
send_command(0x33);
send_command(0x32);
send_command(0x28); // 4 bit mode
send_command(0x0E); // clear the screen
send_command(0x01); // display on cursor on
send_command(0x06); // increment cursor
send_command(0x80); // row 1 column 1
}
#include “lcd.h”
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // stop watchdog timer
lcd_init();
send_string(“Hello”);
send_command(0xC0);
send_string(“World”);
while(1){}
}