#include "HD44780_LCD_PCF8574.h"
#include <Keypad.h>

// I2C LCD at address 0x27, 16 columns x 2 rows
HD44780LCD lcd(2, 16, 0x27, &Wire);

int finalTrialValue = 0;     // Retain the final value globally
int trialValue = 0;
int userInput = 0; // Value input by user through keypad

// Shift register pins
const int latchPin = 10;  // ST_CP (Latch Pin)
const int clockPin = 11;  // SH_CP (Clock Pin)
const int dataPin = 12;   // DS (Data Pin)

// Button pin
const int buttonPin = 2;  // Push button connected to pin 2
const int buttonEnable = 3;

// Keypad setup
const byte ROW_NUM    = 4; // four rows
const byte COLUMN_NUM = 3; // three columns
char keys[ROW_NUM][COLUMN_NUM] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte pin_rows[ROW_NUM] = {4, 5, 6, 7}; 
byte pin_column[COLUMN_NUM] = {8, 9, 13}; 
Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

// Store last displayed values to prevent unnecessary updates
int lastDisplayedVin = -1;
int lastDisplayedVout = -1;

void setup() {
  lcd.PCF8574_LCDInit(lcd.LCDCursorTypeOff);
  lcd.PCF8574_LCDClearScreen();
  lcd.PCF8574_LCDBackLightSet(true);
  lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberTwo, 0);
  lcd.PCF8574_LCDSendString("SAR ADC Demo");

  Serial.begin(9600);

  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(buttonEnable, INPUT_PULLUP);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

  shiftOutData(0);  // Ensure LEDs are off initially
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    if (key >= '0' && key <= '9') {
      userInput = userInput * 10 + (key - '0');  // Build the input number
    } else if (key == '#') {
      // Start simulation when "#" is pressed
      finalTrialValue = sarApproximation(userInput); // Run SAR ADC simulation
    } else if (key == '*') {
      // Reset the user input when "*" is pressed
      userInput = 0;
    }
  }

  // Read and scale input value
  int rawValue = userInput;
  int scaledValue = rawValue;

  // Only update Vin display if value has changed
  if (scaledValue != lastDisplayedVin) {
    char buffer[16];
    sprintf(buffer, "Vin:  %d", scaledValue);
    
    lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberOne, 0);
    lcd.PCF8574_LCDSendString("                ");
    lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberOne, 0);
    lcd.PCF8574_LCDSendString(buffer);
    
    lastDisplayedVin = scaledValue;
  }

  // Start simulation if enabled
  if (digitalRead(buttonEnable) == LOW) {
    finalTrialValue = sarApproximation(trialValue); // Run SAR ADC simulation
  }

  // Display retained final value only if it has changed
  if (finalTrialValue != lastDisplayedVout) {
    char buffer[16];
    sprintf(buffer, "Vout: %d", finalTrialValue);
    
    lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberTwo, 0);
    lcd.PCF8574_LCDSendString("                ");
    lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberTwo, 0);
    lcd.PCF8574_LCDSendString(buffer);
    
    lastDisplayedVout = finalTrialValue;
  }

  delay(100); // Debounce delay
}

int sarApproximation(int rawValue) {
  int scaledValue = rawValue;  // Scale raw value to 8 bits (0–255)
  int approxValue = 0;            // Start approximation with 0
  int finalStepValue = 0;         // Variable to store the final trialValue

  shiftOutData(0);  // Clear Shift Register

  // Wait for the enable button to start the simulation
  while (digitalRead(buttonEnable) == LOW) {
    for (int bit = 7; bit >= 0; bit--) {
      int trialValue = approxValue | (1 << bit);  // Try setting the current bit
      shiftOutData(trialValue);  // Show the current trial value on LEDs
      delay(100);  // Pause to demonstrate the step

  int rawValue = userInput;
  int scaledValue = rawValue;

      char buffer[16];
      sprintf(buffer, "Stp: %d Vref: %d", 8 - bit, trialValue);
      lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberTwo, 0);
      lcd.PCF8574_LCDSendString("                ");  // Clear the line
      lcd.PCF8574_LCDGOTO(lcd.LCDLineNumberTwo, 0);
      lcd.PCF8574_LCDSendString(buffer);

      // Retain the current bit if the trialValue is valid
      if (trialValue < scaledValue) {
        approxValue = trialValue;
      }

      // Retain the final trialValue at the 8th step
      if (bit == 0) {
        finalStepValue = trialValue;  // Save the 8th step trialValue
      }

      // Wait for button press to advance the next bit
      while (digitalRead(buttonPin) == HIGH) {
        // Wait for button to be pressed (LOW state)
      }
      delay(200);  // Small debounce delay
    }
  }

  return finalStepValue;  // Return the final trial value from the 8th step
}

void shiftOutData(byte data) {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, data);
  digitalWrite(latchPin, HIGH);
}