Project: Digital Counter using PIC16F877A and 16×2 LCD

Project: Digital Counter using PIC16F877A and 16×2 LCD

1. Introduction

This project demonstrates how to interface a 16×2 LCD with a PIC16F877A microcontroller and implement a simple digital counter controlled by a push button. When the button is pressed, the count increments and is displayed on the LCD.

Real-world Applications:

• Digital tally counters
• Event counting in industrial applications
• Simple user input interface for embedded systems

2. Learning Objectives

By completing this project, you will learn:

• How to interface a 16×2 LCD with a PIC microcontroller
• How to configure GPIO pins as digital inputs and outputs
• How to implement button debouncing in firmware
• How to program in MikroC for PIC

3. Components Required

• PIC16F877A microcontroller
• 16×2 LCD Display
• Push button switch
• 10kΩ Potentiometer (for LCD contrast control)
• 4.7kΩ Pull-down resistor (for push button)
• Crystal Oscillator 20MHz
• 2x 22pF Capacitors
• Power supply (5V DC)
• Breadboard & Jumper wires

4. Circuit Diagram Description

• The 16×2 LCD is connected to the PORTD of the PIC16F877A (D4-D7 for data, RS and E for control signals).
• The push button is connected to PORTB.0 with a pull-down resistor to ensure a stable LOW state when not pressed.
• A 10kΩ potentiometer is connected to the VEE pin of the LCD to control contrast.
• A 20MHz crystal oscillator is connected to OSC1 and OSC2 with 22pF capacitors for stable clock operation.

5. Code Implementation (MikroC for PIC)

#include <built_in.h>

sbit LCD_RS at RD2_bit;
sbit LCD_EN at RD3_bit;
sbit LCD_D4 at RD4_bit;
sbit LCD_D5 at RD5_bit;
sbit LCD_D6 at RD6_bit;
sbit LCD_D7 at RD7_bit;

sbit LCD_RS_Direction at TRISD2_bit;
sbit LCD_EN_Direction at TRISD3_bit;
sbit LCD_D4_Direction at TRISD4_bit;
sbit LCD_D5_Direction at TRISD5_bit;
sbit LCD_D6_Direction at TRISD6_bit;
sbit LCD_D7_Direction at TRISD7_bit;

unsigned int count = 0; // Counter variable

void main() {
    TRISB0_bit = 1;  // Set RB0 as input (button)
    TRISD = 0x00;    // Set PORTD as output (LCD)
    Lcd_Init();      // Initialize LCD
    Lcd_Cmd(_LCD_CLEAR);   // Clear LCD screen
    Lcd_Cmd(_LCD_CURSOR_OFF); // Turn off cursor
    
    Lcd_Out(1, 1, "Counter:");
    
    while (1) {
        if (RB0_bit == 1) {  // If button is pressed
            Delay_ms(200);  // Debouncing delay
            if (RB0_bit == 1) {
                count++;   // Increment counter
                Lcd_Out(2, 1, "      ");  // Clear previous count
                Lcd_Out(2, 1, IntToStr(count));  // Display new count
                while(RB0_bit == 1); // Wait until button is released
            }
        }
    }
}

6. Troubleshooting Tips

Common Issues & Solutions

1. LCD displays garbage characters
   • Possible Cause: Incorrect contrast setting
   • Solution: Adjust 10kΩ potentiometer
2. LCD is blank
   • Possible Cause: Improper LCD connections
   • Solution: Check VCC, GND, and control lines
3. Counter not incrementing
   • Possible Cause: Button bouncing issue
   • Solution: Increase debounce delay
4. Microcontroller not working
   • Possible Cause: Clock not oscillating
   • Solution: Check crystal and capacitors
5. Unexpected resets
   • Possible Cause: Power fluctuations
   • Solution: Use capacitor (100nF) across VCC and GND

7. Extensions & Further Improvements

• Add a reset button to reset the count
• Implement EEPROM storage to save count even after power loss
• Add a buzzer for audio feedback when the button is pressed
• Interface with a seven-segment display instead of LCD
• Use an interrupt instead of polling for button press

This project provides a solid foundation for working with PIC microcontrollers, LCD interfacing, and push-button inputs. Keep experimenting and improving your design!