#include <avr/io.h>          // AVR input/output library
#include <util/delay.h>      // Delay functions library
#include <stdlib.h>          // Standard library for utility functions

// Target: Atmega2560 @ 16 MHz (tested)
//---------------DEFINITIONS--------------------------

// LCD pin configuration
#define LCD_RS_SIGNAL        0   // PC0 pin37 of uC to LCD RS - pin 4 of LCD
#define LCD_RW_SIGNAL        1   // PC1 pin36 of uC (don't connect) to LCD R/W - currently grounded
#define LCD_ENABLE_SIGNAL    2   // PC1 pin36 of uC to LCD E - pin 6 of LCD
#define LCD_C4_SIGNAL        4   // PC4 pin33 of uC to LCD D4 - pin 11 of LCD
#define LCD_C5_SIGNAL        5   // PC5 pin32 of uC to LCD D5 - pin 12 of LCD
#define LCD_C6_SIGNAL        6   // PC6 pin31 of uC to LCD D6 - pin 13 of LCD
#define LCD_C7_SIGNAL        7   // PC7 pin30 of uC to LCD D7 - pin 14 of LCD

#define LCD_Dir DDRC         // Define LCD data port direction
#define LCD_Port PORTC       // Define LCD data port
#define RS PC0               // Define Register Select (data reg./command reg.) signal pin
#define EN PC1               // Define Enable signal pin

// Function to send a command to the LCD
void LCD_Command(unsigned char cmnd) {
    LCD_Port = (LCD_Port & 0x0F) | (cmnd & 0xF0); // Send the upper nibble of the command
    LCD_Port &= ~(1<<RS);        // RS=0, command register
    LCD_Port |= (1<<EN);         // Enable pulse
    _delay_us(1);                // Small delay
    LCD_Port &= ~(1<<EN);        // Disable pulse
    _delay_us(200);              // Delay for command to process
    LCD_Port = (LCD_Port & 0x0F) | (cmnd << 4);  // Send the lower nibble of the command
    LCD_Port |= (1<<EN);         // Enable pulse
    _delay_us(1);                // Small delay
    LCD_Port &= ~(1<<EN);        // Disable pulse
    _delay_ms(2);                // Delay for command to process
}

// Function to send a character to the LCD
void LCD_Char(unsigned char data) {
    LCD_Port = (LCD_Port & 0x0F) | (data & 0xF0); // Send the upper nibble of the data
    LCD_Port |= (1<<RS);        // RS=1, data register
    LCD_Port |= (1<<EN);        // Enable pulse
    _delay_us(1);               // Small delay
    LCD_Port &= ~(1<<EN);       // Disable pulse
    _delay_us(200);             // Delay for data to process
    LCD_Port = (LCD_Port & 0x0F) | (data << 4); // Send the lower nibble of the data
    LCD_Port |= (1<<EN);        // Enable pulse
    _delay_us(1);               // Small delay
    LCD_Port &= ~(1<<EN);       // Disable pulse
    _delay_ms(2);               // Delay for data to process
}

// Function to send a string to the LCD
void LCD_String(char *str) {
    while (*str) {              // Loop until the end of the string
        LCD_Char(*str++);       // Send each character one by one
    }
}

// Function to initialize the LCD
void LCD_Init(void) {
    LCD_Dir = 0xFF;             // Make LCD command port direction as output
    _delay_ms(20);              // LCD Power ON delay always >15ms

    LCD_Command(0x33);          // Initialize LCD for 4-bit mode
    LCD_Command(0x32);          // Initialize LCD for 4-bit mode
    LCD_Command(0x28);          // Use 2 line and initialize 5*7 matrix in 4-bit mode
    LCD_Command(0x0c);          // Display ON, cursor OFF
    LCD_Command(0x06);          // Increment cursor (shift cursor to right)
    LCD_Command(0x01);          // Clear display screen
    _delay_ms(2);               // Delay for command to process
    LCD_Command(0x80);          // Move cursor to the first row and first column
}

// Function to initialize the ADC (Analog to Digital Converter)
void ADC_Init() {
    DDRA = 0x00;                // Make ADC port as input
    ADCSRA = (1<<ADEN) | (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0); // Enable ADC and set prescaler to divide by 128
    ADMUX = (1<<REFS0);         // Set reference voltage to AVcc and select ADC channel 0
}

// Function to read the value from the specified ADC channel
int ADC_Read(char channel) {
    ADMUX = (ADMUX & 0x07) | (channel & 0x07); // Set the ADC channel to read from (0 to 7)
    if (channel & 0x08) { // Check if the channel is 8 or above
        ADCSRB |= (1 << MUX5); // Set MUX5 for channels 8-15
    } else {
        ADCSRB &= ~(1 << MUX5); // Clear MUX5 for channels 0-7
    }
    ADCSRA |= (1<<ADSC);        // Start the ADC conversion
    while (ADCSRA & (1<<ADSC)); // Wait until the conversion is complete
    return ADCW;                // Return the ADC conversion result
}
// Main function
int main() 
{
    LCD_Init();                 // Initialize the LCD
    ADC_Init();                 // Initialize the ADC
    
    char Voltage[10];           // Buffer to hold the voltage string
    float volt;                 // Variable to hold the measured voltage
    int D;                      // Variable to hold the ADC value
    
    while (1) {
        D = ADC_Read(8);        // Read the ADC value from channel 0
        volt = ((float)D * 0.00488); // Convert the ADC value to voltage (assuming 5V reference and 10-bit resolution)
        
        LCD_Command(0x01);      // Clear the LCD display
        
        dtostrf(volt, 8, 3, Voltage); // Convert the voltage to a string with 8 digits and 3 decimal places
        
        LCD_String(Voltage);    // Display the voltage on the LCD
        LCD_Command(0xC0);      // Move the cursor to the second line of the LCD
        
        _delay_ms(500);         // Wait for 500 milliseconds before the next read
    }

    return 0;
}