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ATMega16 AVR Microcontroller LCD Digital Clock

The ATMega16 LCD Digital Clock

In this ATMega16 AVR project we will be designing and implementing a digital clock with the aid of a Atmel AVR ATMega16 microcontroller and an alphanumeric liquid crystal display (LCD).


Note: Although this AVR project was designed around the ATMega16 the project could have utilized another microcontroller such as an ATMega32, ATMega8515, etc.


ATMega16 LCD Digital Clock Operation
Our digital clock operates as follows. When the circuit is powered up the clock starts at "00:00:00" for "HH:MM:SS". There are two push-button switches used to set the time. Switch SW1 is for setting the minutes, when this button is pressed the minutes in increase until it reaches 59 then reset and start counting from 0. Switch SW2 is for setting the hours.


ATMega16 LCD Digital Clock Hardware Description

The figure below gives the circuit diagram for the ATmega16 LCD Digital Clock.


ATMega16 AVR Microcontroller LCD Digital Clock Circuit

Important Note: In order for our digital clock to work correctly the internal oscillator of the ATMega16 AVR microcontroller must be enabled and set to 4MHz.

ATMega16 LCD Digital Clock Software

Below is the AVR C implementation of the entire code for the ATMega16 based LCD digital clock. The code was implemented and built using AVR Studio 5. Be reminded that the internal clock of the ATMega16 microcontroller should be enabled and programmed to operate at 4MHz for the AVR C code to operate correctly. A video of the LCD digital clock in operation is presented at the end of this page. 


/*
 * LCD-Digital-Clock.c
 *
 * Written in AVR Studio 5
 * Compiler: AVR GNU C Compiler (GCC)
 *
 * Created: 12/22/2011 6:34:36 PM
 * Author: AVR Tutorials
 * Website: AVR-Tutorials.com
 */ 
 
#define F_CPU     4000000UL
#include <avr/delay.h>
#include <avr/io.h>
#include <string.h>
#include <avr/interrupt.h>
 
/*Global Variables Declarations*/
unsigned char hours = 0;
unsigned char minutes = 0;
unsigned char seconds = 0;
char time[] = "00:00:00";
 
/*LCD function declarations */
void LCD_send_command(unsigned char cmnd);
void LCD_send_data(unsigned char data);
void LCD_init();
void LCD_goto(unsigned char y, unsigned char x);
void LCD_print(char *string);
void LCD_update_time(void);
 
/*Timer Counter 1 Compare Match A Interrupt Service Routine/Interrupt Handler*/
ISR(TIMER1_COMPA_vect);
 
#define LCD_DATA_PORT     PORTB
#define LCD_DATA_DDR      DDRB
#define LCD_DATA_PIN      PINB
 
#define LCD_CNTRL_PORT    PORTC
#define LCD_CNTRL_DDR     DDRC
#define LCD_CNTRL_PIN     PINC
 
#define LCD_RS_PIN                5
#define LCD_RW_PIN                6
#define LCD_ENABLE_PIN            7
#define SET_HOUR          3
#define SET_MINUTE                4
 
int main(void)
{
        unsigned char i; 
 
    LCD_init();
        LCD_goto(1,2);
        LCD_print("AVR-Tutorials");
        LCD_goto(2,4);
        LCD_print(time);
 
        LCD_CNTRL_PORT = (1<<SET_HOUR | 1<<SET_MINUTE);
 
        TCCR1B = (1<<CS12|1<<WGM12);
        OCR1A = 15625-1;
        TIMSK = 1<<OCIE1A;
        sei();
 
        while(1)
    {
                if(!(LCD_CNTRL_PIN & (1<<SET_HOUR)))
                {
                        hours++;
                        if(hours > 23)
                                hours = 0;
                }
                if(!(LCD_CNTRL_PIN & (1<<SET_MINUTE)))
                {
                        minutes++;
                        if(minutes > 59)
                                minutes = 0;
                }
                _delay_ms(250);
        }
}
 
/* This function sends a command 'cmnd' to the LCD module*/
void LCD_send_command(unsigned char cmnd)
{
        LCD_DATA_PORT = cmnd;
        LCD_CNTRL_PORT &= ~(1<<LCD_RW_PIN);
        LCD_CNTRL_PORT &= ~(1<<LCD_RS_PIN);
 
        LCD_CNTRL_PORT |= (1<<LCD_ENABLE_PIN);
        _delay_us(2);
        LCD_CNTRL_PORT &= ~(1<<LCD_ENABLE_PIN);
        _delay_us(100);
}
 
/* This function sends the data 'data' to the LCD module*/
void LCD_send_data(unsigned char data)
{
        LCD_DATA_PORT = data;
        LCD_CNTRL_PORT &= ~(1<<LCD_RW_PIN);
        LCD_CNTRL_PORT |= (1<<LCD_RS_PIN);
 
        LCD_CNTRL_PORT |= (1<<LCD_ENABLE_PIN);
        _delay_us(2);
        LCD_CNTRL_PORT &= ~(1<<LCD_ENABLE_PIN);
        _delay_us(100);
}
 
void LCD_init()
{
        LCD_CNTRL_DDR = 0xFF;
        LCD_CNTRL_PORT = 0x00;
        LCD_DATA_DDR = 0xFF;
        LCD_DATA_PORT = 0x00;
 
        _delay_ms(10);
        LCD_send_command(0x38);
        LCD_send_command(0x0C);
        LCD_send_command(0x01);
        _delay_ms(10);
        LCD_send_command(0x06);
}
 
/* This function moves the cursor the line y column x on the LCD module*/
void LCD_goto(unsigned char y, unsigned char x)
{
        unsigned char firstAddress[] = {0x80,0xC0,0x94,0xD4};
 
        LCD_send_command(firstAddress[y-1] + x-1);
        _delay_ms(10);      
}
 
void LCD_print(char *string)
{
        unsigned char i;
 
        while(string[i]!=0)
        {
                LCD_send_data(string[i]);
                i++;
        }
}
void LCD_update_time()
{
        unsigned char temp;
 
        LCD_goto(2,4);
 
        itoa(hours/10,temp,10);
        LCD_print(temp);
        itoa(hours%10,temp,10);
        LCD_print(temp);
        LCD_print(":");
 
        itoa(minutes/10,temp,10);
        LCD_print(temp);
        itoa((minutes%10),temp,10);
        LCD_print(temp);
        LCD_print(":");
 
        itoa(seconds/10,temp,10);
        LCD_print(temp);
        itoa(seconds%10,temp,10);
        LCD_print(temp);
}
/*Timer Counter 1 Compare Match A Interrupt Service Routine/Interrupt Handler*/
ISR(TIMER1_COMPA_vect)
{             
        seconds++;
 
        if(seconds == 60)
        {
                seconds = 0;
                minutes++;
        }
        if(minutes == 60)
        {
                minutes = 0;
                hours++;           
        }
        if(hours > 23)
                hours = 0;
 
        LCD_update_time();
}


ATMega16 LCD Digital Clock Video



AVR Tutorials hopes this AVR project on the ATMega16 LCD Digital Clock was benificial to you and looks forward to your continued visits for all your AVR microcontroller projects needs.