#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// Define OLED display parameters
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1  // Reset pin is not used in I2C mode
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Define analog pin and voltage divider ratio
#define BATTERY_PIN 34  // ADC pin where battery voltage is read
#define VOLTAGE_DIVIDER_RATIO 3.0  // Assuming a 12V battery and a divider that scales it down

// Battery voltage limits
#define BATTERY_MIN_VOLTAGE 1.5
#define BATTERY_MAX_VOLTAGE 13.5

void setup() {
  // Initialize serial for debugging
  Serial.begin(115200);

  // Initialize OLED display with I2C address 0x3C
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);  // Loop forever if the display cannot be initialized
  }

  // Clear the display buffer
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
}

void loop() {
  // Read the raw analog value from the battery pin
  int rawValue = analogRead(BATTERY_PIN);

  // Convert raw value to actual battery voltage
  float batteryVoltage = rawValue / 4095.0 * 3.3 * VOLTAGE_DIVIDER_RATIO;

  // Calculate the battery level as a percentage
  float batteryLevel = (batteryVoltage - BATTERY_MIN_VOLTAGE) / (BATTERY_MAX_VOLTAGE - BATTERY_MIN_VOLTAGE) * 100;
  if (batteryLevel > 100) batteryLevel = 100;
  if (batteryLevel < 0) batteryLevel = 0;

  // Display battery voltage and percentage on the OLED
  display.clearDisplay();
  
  display.setCursor(0, 0);
  display.print("Battery Voltage: ");
  display.print(batteryVoltage);
  display.println("V");

  display.setCursor(0, 20);
  display.print("Battery Level: ");
  display.print(batteryLevel);
  display.println("%");

  // Draw a battery level bar
  int barWidth = batteryLevel / 100.0 * 100;
  display.drawRect(0, 40, 100, 10, WHITE);  // Battery bar outline
  display.fillRect(0, 40, barWidth, 10, WHITE);  // Filled battery bar
  
  display.display();

  // Print values for debugging on the Serial Monitor
  Serial.print("Battery Voltage: ");
  Serial.print(batteryVoltage);
  Serial.print(" V, ");
  Serial.print("Battery Level: ");
  Serial.print(batteryLevel);
  Serial.println("%");

  // Delay for a short period before reading again
  delay(1000);
}