#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define ENCODER_A 32 // Pin for Encoder A
#define ENCODER_B 33 // Pin for Encoder B

volatile int encoder_value = 0; // Global variable for storing the encoder position
int last_encoder_value = 0; // Store the last encoder value
unsigned long last_time = 0; // Store the last time in milliseconds
float motor_rpm = 0; // Variable for storing the motor speed in RPM

// Encoder specification
const int PPR = 200; // Pulses per revolution (set according to your encoder's specification)

// Initialize the LCD (address 0x27 for a 16x2 LCD)
LiquidCrystal_I2C lcd(0x27, 16, 2);

void encoder_isr() {
  // Reading the current state of encoder A and B
  int A = digitalRead(ENCODER_A);
  int B = digitalRead(ENCODER_B);

  // If the state of A changed, it means the encoder has been rotated
  if ((A == HIGH) != (B == LOW)) {
    encoder_value--;
  } else {
    encoder_value++;
  }
}

void setup() {
  Serial.begin(115200); // Initialize serial communication
  
  // Initialize the encoder pins
  pinMode(ENCODER_A, INPUT_PULLUP);
  pinMode(ENCODER_B, INPUT_PULLUP);

  // Initialize the LCD and turn on the backlight
  lcd.init();
  lcd.backlight();
  
  // Attach the ISR for encoder pin A
  attachInterrupt(digitalPinToInterrupt(ENCODER_A), encoder_isr, CHANGE); // Pin for the encoder A

  // Initialize the last time
  last_time = millis();
}

void loop() {
  // Get the current time
  unsigned long current_time = millis();
  
  // Calculate the time difference (delta_time) in seconds
  float delta_time = (current_time - last_time) / 100.0;

  // Prevent division by zero by setting a minimum time threshold
  if (delta_time < 0.001) {
    delta_time = 0.001; // Set a minimum time to avoid division by zero
  }
  
  // Calculate the encoder difference (delta_encoder)
  int delta_encoder = encoder_value - last_encoder_value;

  // Calculate the motor speed in RPM (ensure that PPR is non-zero)
  if (PPR != 0) {
    motor_rpm = (delta_encoder / (float)PPR) / delta_time * 60.0;
  }

  // Update the last encoder value and time
  last_encoder_value = encoder_value;
  last_time = current_time;

  // Print encoder value and RPM to Serial Monitor
  Serial.print("Encoder value: ");
  Serial.println(encoder_value);
  Serial.print("Motor RPM: ");
  Serial.println(motor_rpm);
  
  // Display encoder value and RPM on LCD
  lcd.clear();  // Clear previous data from the screen
  lcd.setCursor(0, 0);  // Set cursor to the first column, first row
  lcd.print("Enc Value: ");
  lcd.print(encoder_value);
  lcd.setCursor(0, 1);  // Set cursor to the first column, second row
  lcd.print("Motor RPM: ");
  lcd.print(motor_rpm);

  delay(200); // Adjust the delay to control update frequency
}