AVRFreaks.net

#include <avr/io.h>
#include <avr/interrupt.h>
#define F_CPU 100000UL    // default speed for delay.h (1Mhz)
#include <util/delay.h>
   
int main(void) {   
    // Let LCD Boot up
    _delay_ms(4000);

    // Enable PB0, 1, and 2 for output (RS, RW, EN)
    DDRB = (1 << PB0) | (1 << PB1) | (1 << PB2);

    // Enable PD0 - PD7 (D0 - D7 on LCD)
    DDRD = 0xFF;
    PORTD = 0x00;

    // Let LCD boot up
    _delay_ms(400);

    // Set RS to high
    PORTB = (1 << PB0);
    _delay_ms(40);

    // Set EN to high
    PORTB |= (1 << PB2);
    _delay_ms(40);

    // Turn Display ON
    PORTD = 0x0F;
    _delay_ms(40);          // datasheet specified at least 40us

    // Set EN to low
    PORTB &= ~(1 << PB2);

    while(1) {

    }   

    return 0;
}

#include <avr/io.h>

/*
 * Permission to use, copy, modify, distribute and sell this software and its documentation for any purpose is hereby granted without fee, provided that the below copyright notice appears in all copies and that both the copyright notice and this permission notice appear in supporting documentation. Livingston Electronics makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.
 *
 *
 * 8 BIT LCD control program
 * Written by Carl W. Livingston
 * Modified in a attempt to get working by some other guy
 * Copyright Carl W. Livingston
 * microcarl@roadrunner.com
 * AVR Freaks member - microcarl
 * January 02, 2007
 * */

/*   //// From the LCD perspective \\\\
      LCD:R/W <-- PORTD:4
      LCD:RS <-- PORTD:5
      LCD:E <-- PORTD:6
      N/A <-> PORTD:7

      LCD:R/W <-- PORTD:4
      LCD:RS <-- PORTD:5
      LCD:E <-- PORTD:6
      LCD:Vee <-- CONTRAST
      LCD:DB0 <-- PORTB:0
      LCD:DB1 <-- PORTB:1
      LCD:DB2 <-- PORTB:2
      LCD:DB3 <-- PORTB:3
      LCD:DB4 <-- 4.7K Ohm <-- PORTx:4
      LCD:DB5 <-- 4.7K Ohm <-- PORTx:5
      LCD:DB6 <-- 4.7K Ohm <-- PORTx:6
      LCD:DB7 <-- 4.7K Ohm <-- PORTx:7

//// From the I/O PORTD perspective \\\\
      PORTD:4 --> LCD:R/W
      PORTD:5 --> LCD:RS
      PORTD:6 --> LCD:E
      PORTD:7 <-> N/A   
   
      PORTB:0 --> LCD:DB0
      PORTB:1 --> LCD:DB1
      PORTB:2 --> LCD:DB2
      PORTB:3 --> LCD:DB3
      PORTB:4 --> 4.7K Ohm --> LCD:DB4
      PORTB:5 --> 4.7K Ohm --> LCD:DB5
      PORTB:6 --> 4.7K Ohm --> LCD:DB6
      PORTB:7 --> 4.7K Ohm --> LCD:DB7
*/

/*************************************************************/
/*************************************************************/
// If you want to use a different I/O port for LCD control & data,
// do it here!!!
#define LCD_DATA_OUT PORTB
#define LCD_DATA_IN PINB
#define LCD_DATA_DDR DDRB

#define LCD_CONTROL_OUT PORTD
#define LCD_CONTROL_IN PIND
#define LCD_CONTROL_DDR DDRD

// Define LCD Read/Write as PORTx, 0x10;
#define LCD_RW 4
// Define LCD Register Select as PORTx, 0x20;
#define LCD_RS 5
// Define LCD Enable as PORTx, 0x40;
#define LCD_E 6
/*************************************************************/
/*************************************************************/

// LCD busy status bit
#define LCD_BUSY 7
// LED control bit
#define LED 1
// BAUD rate control bits
#define J_1 2
#define J_2 3
#define CGRAM 6

// Turn on power to the display, no cursor
#define   PWR_ON   0x0C
// Set 8 data bits
#define   DATA_8   0x30
// Set 8 data bits, 4 display lines
#define   LINE_8x4   0x38
// Clear display command     
#define CLR_DSP 0x01
// Character generator RAM command
#define REG_MODE 0xFE

#define NULL 0x00

void LCD_Delay (unsigned int);
void LCD_PutCmd (char);
void LCD_PutChar (char);
char LCD_BusyWait (void);
void IO_INIT (void);
void LCD_INIT (void);

int main (void) {
          // Initialize the Mega16 I/O
          IO_INIT ();
          // Initialize the HD44780 LCD controller
          LCD_INIT ();
   
          while (1) {
              LCD_PutChar('b');
          }         
}

// Clock cycle = 67nS @ 14.7456MHz   
// Delay resolution ~ 1uS @ 14.7456MHz
void LCD_Delay (unsigned int d) {
               while (d-- != 0)
               ;
               asm("nop"); // Make the delay time a bit closer to the predicted delay time.
                           // Experimentally setup with an Oscilloscope.
}

void LCD_PutCmd (char Cmd) {
    LCD_CONTROL_OUT &= ~(1<<LCD_RS);
    LCD_BusyWait();
    LCD_DATA_OUT = Cmd;   
    asm ("nop");   
    LCD_CONTROL_OUT |= (1<<LCD_E);
    asm ("nop"); // PWeh must be 230nS minimum
    asm ("nop"); // nop = 67nS @ 14.7456MHz   
    asm ("nop");
    asm ("nop"); // Here, E = 271nS @ 14.7456MHz   
    LCD_CONTROL_OUT &= ~(1<<LCD_E);
    asm ("nop");
    LCD_CONTROL_OUT |= (1<<LCD_RS);
}

void LCD_PutChar (char c) {
    LCD_CONTROL_OUT &= ~(1<<LCD_RS);
    LCD_BusyWait();
    LCD_CONTROL_OUT |= (1<<LCD_RS);
    LCD_DATA_OUT = c;
    asm ("nop");         
    LCD_CONTROL_OUT |= (1<<LCD_E);
    asm ("nop"); // PWeh must be 230nS minimum
    asm ("nop"); // nop = 67nS @ 14.7456MHz   
    asm ("nop");
    asm ("nop"); // Here, E = 271nS @ 14.7456MHz
    LCD_CONTROL_OUT &= ~(1<<LCD_E);
}

char LCD_BusyWait (void) {
    unsigned char LCDStatus;
    LCD_DATA_DDR = 0x00; // Set LCD data port to inputs
    LCD_CONTROL_OUT |= (1<<LCD_RW);
    asm ("nop");
    do {
       LCD_CONTROL_OUT |= (1<<LCD_E);   
      asm ("nop"); // PWeh must be 230nS minimum
      asm ("nop"); // nop = 67nS @ 14.7456MHz   
      asm ("nop");   
      asm ("nop"); // Here, E = 271nS @ 14.7456MHz
      LCDStatus = LCD_DATA_IN;
      LCD_CONTROL_OUT &= ~(1<<LCD_E);
    } while ((LCDStatus & (1<<LCD_BUSY)) == (1<<LCD_BUSY));
    LCD_CONTROL_OUT &= ~(1<<LCD_RW);   
    LCD_DATA_DDR |= 0xFF; // Set LCD data port to outputs     
    return (LCDStatus);
}         

void IO_INIT (void) {
    LCD_Delay (60000); // Wait for the LCD display to boot up
    // Set J_2:J_1 PULL-UPS active
    LCD_CONTROL_OUT = (1<<J_2) | (1<<J_1);
    // Set LCD_control J_2:J_1 to inputs   
    LCD_CONTROL_DDR = 0xF2;
    LCD_CONTROL_OUT |= (1<<LCD_RS); // Set LCD_RS HIGH   
    // Delay resolution ~ 1uS @ 14.7456MHz         
    LCD_Delay (15000); // Need 15mS delay for LCD to power up

    // Initialize the AVR controller I/O
    LCD_DATA_DDR = 0xFF; // Set LCD_DATA_OUT as all outputs
    LCD_DATA_OUT = 0x00; // Set LCD_DATA_OUT to logic low
}

void LCD_INIT (void) {
    // Initialize the LCD controller
    LCD_PutCmd (LINE_8x4); // Set 8 bit data, 4 display lines
    LCD_PutCmd (CLR_DSP); // Power up the display
    LCD_PutCmd (PWR_ON); // Power up the display
    LCD_Delay (30000);
    LCD_BusyWait();
}