AVR Calculator with LCD Display

Overview

This project implements a basic calculator using an AVR microcontroller and an LCD display. The calculator takes input via an analog-to-digital converter (ADC) and performs basic arithmetic operations. It can add, subtract, multiply, and divide numbers, displaying the results on the LCD.

Hardware Requirements

• AVR microcontroller (e.g., ATmega328)
• LCD display (compatible with the LCD.h library)
• Arduino 4x4 Keypad
• Power supply

Software Requirements

• Arduino 1.8.9 or higher
• LCD.h library (download folder and upload into libraries)

Code Explanation

Includes and Macros

#include <avr/io.h>
#include <avr/interrupt.h>
#include <LCD.h>

#define checkbit(x, y) ((x) & (y)) // Macro to check a specific bit in a byte
#define bitn(p) (0x01 << (p)) // Macro to generate a bitmask for a given bit position

Function Definitions

Initialize ADC

void init_ADC() {
    ADMUX = 0x44; // Select Vref=AVcc and select channel 4 (PC4)
    ADCSRA = 0xC7; // Enable ADC, start conversion, auto trigger enable, interrupt enable
}

Read ADC Value

long read_ADC() {
    ADCSRA |= (1 << ADSC); // Start conversion
    while (checkbit(ADCSRA, (1 << ADSC))); // Wait for conversion to complete
    return ADCW; // Read ADC value
}

Clear LCD and Reset Variables

void clear() {
    lcd.cmd(0x01); // Clear LCD
    num1 = 0;
    num2 = 0;
    operatorz = ' ';
    result = 0;
    average = 0;
    i = 0;
    isSecondNumber = false;
}

Preform Operations

void performOperation() {
    switch (operatorz) {
        case '+':
            result = num1 + num2;
            break;
        case '-':
            result = num1 - num2;
            break;
        case '*':
            result = num1 * num2;
            break;
        case '/':
            if (num2 != 0) {
                result = num1 / num2;
            } else {
                result = 0; // Handle division by zero
            }
            break;
        default:
            result = num1; // Default to first number if no operator
            break;
    }
    lcd.string("=");
    lcd.showvalue(result); // Display the result on the LCD
    _delay_ms(500);
    clear(); // Reset for next calculation
}

Compare ADC Values to determine what key was pressed

void compare() {
    if (average > 519 && average < 523) {
        lcd.string("1");
        if (isSecondNumber) num2 = num2 * 10 + 1; else num1 = num1 * 10 + 1;
    } else if (average > 690 && average < 694) {
        lcd.string("2");
        if (isSecondNumber) num2 = num2 * 10 + 2; else num1 = num1 * 10 + 2;
    } else if (average > 766 && average < 770) {
        lcd.string("3");
        if (isSecondNumber) num2 = num2 * 10 + 3; else num1 = num1 * 10 + 3;
    } else if (average > 1018 && average < 1023) {
        lcd.string("+");
        operatorz = '+';
        isSecondNumber = true;
    } else if (average > 489 && average < 493) {
        lcd.string("4");
        if (isSecondNumber) num2 = num2 * 10 + 4; else num1 = num1 * 10 + 4;
    } else if (average > 639 && average < 642) {
        lcd.string("5");
        if (isSecondNumber) num2 = num2 * 10 + 5; else num1 = num1 * 10 + 5;
    } else if (average > 704 && average < 708) {
        lcd.string("6");
        if (isSecondNumber) num2 = num2 * 10 + 6; else num1 = num1 * 10 + 6;
    } else if (average > 910 && average < 914) {
        lcd.string("-");
        operatorz = '-';
        isSecondNumber = true;
    } else if (average > 473 && average < 478) {
        lcd.string("7");
        if (isSecondNumber) num2 = num2 * 10 + 7; else num1 = num1 * 10 + 7;
    } else if (average > 611 && average < 615) {
        lcd.string("8");
        if (isSecondNumber) num2 = num2 * 10 + 8; else num1 = num1 * 10 + 8;
    } else if (average > 671 && average < 675) {
        lcd.string("9");
        if (isSecondNumber) num2 = num2 * 10 + 9; else num1 = num1 * 10 + 9;
    } else if (average > 856 && average < 869) {
        lcd.string("*");
        operatorz = '*';
        isSecondNumber = true;
    } else if (average > 461 && average < 465) {
        clear();
    } else if (average > 591 && average < 595) {
        lcd.string("0");
        if (isSecondNumber) num2 = num2 * 10 + 0; else num1 = num1 * 10 + 0;
    } else if (average > 817 && average < 822) {
        lcd.string("/");
        operatorz = '/';
        isSecondNumber = true;
    } else if (average > 647 && average < 650) {
        performOperation();
    }
    _delay_ms(300); // Debounce delay
}

Setup and Usage

1. Hardware Setup:

• Connect the LCD display to the appropriate pins on the AVR microcontroller.
• Connect the potentiometer or buttons to the analog input pins for ADC readings.
• Ensure all connections are secure and correctly wired. Software Setup:

2. Software Setup:

• Include the LCD.h library in your project.
• Compile the code using AVR-GCC.
• Upload the compiled code to the AVR microcontroller using AVRDUDE.

Additional Notes

Ensure the ADC values for button presses or potentiometer ranges are correctly calibrated. Modify the compare() function if the ADC values differ based on your specific hardware setup. This code assumes a basic understanding of AVR programming and electronics.