#include <Wire.h>

// I2C addresses
#define RTC_ADDR 0x68     // DS1307 RTC
#define MPU_ADDR 0x68     // MPU6050

void setup() {
  Serial.begin(115200);
  Wire.begin();  // ESP32 I2C Master
  delay(1000);
  Serial.println("I2C: RTC + MPU6050 Example");

  // ---- Wake up MPU6050 ----
  Wire.beginTransmission(MPU_ADDR);
  Wire.write(0x6B);   // Power management register
  Wire.write(0x00);   // Wake up sensor
  Wire.endTransmission();

  // ---- Set time in RTC (One time only) ----
  // Format: Seconds, Minutes, Hours, Day, Date, Month, Year
  setRTCtime(0, 30, 12, 2, 3, 9, 25); // 12:30:00 3-Sep-2025 Wednesday
}

void loop() {
  // 1. Read time from RTC
  readRTCtime();

  // 2. Read accel X from MPU6050
  readMPU();

  delay(2000);
}

// ---- Function to set RTC time ----
void setRTCtime(byte sec, byte min, byte hr, byte day, byte date, byte month, byte year) {
  Wire.beginTransmission(RTC_ADDR);
  Wire.write(0x00); // Start at register 0
  Wire.write(decToBcd(sec));
  Wire.write(decToBcd(min));
  Wire.write(decToBcd(hr));
  Wire.write(decToBcd(day));
  Wire.write(decToBcd(date));
  Wire.write(decToBcd(month));
  Wire.write(decToBcd(year));
  Wire.endTransmission();
}

// ---- Function to read RTC time ----
void readRTCtime() {
  Wire.beginTransmission(RTC_ADDR);
  Wire.write(0x00);
  Wire.endTransmission();
  Wire.requestFrom(RTC_ADDR, 7);

  byte sec = bcdToDec(Wire.read() & 0x7F);
  byte min = bcdToDec(Wire.read());
  byte hr  = bcdToDec(Wire.read());
  Wire.read(); // Day of week, ignore
  byte date = bcdToDec(Wire.read());
  byte month = bcdToDec(Wire.read());
  byte year = bcdToDec(Wire.read());

  Serial.print("Time: ");
  Serial.print(hr); Serial.print(":");
  Serial.print(min); Serial.print(":");
  Serial.print(sec);
  Serial.print("  Date: ");
  Serial.print(date); Serial.print("/");
  Serial.print(month); Serial.print("/20");
  Serial.println(year);
}

// ---- Function to read MPU6050 ----
void readMPU() {
  Wire.beginTransmission(MPU_ADDR);
  Wire.write(0x3B); // ACCEL_XOUT_H register
  Wire.endTransmission(false);
  Wire.requestFrom(MPU_ADDR, 2, true);

  if (Wire.available() == 2) {
    int16_t accelX = (Wire.read() << 8) | Wire.read();
    Serial.print("Accel X: ");
    Serial.println(accelX);
  }
}

// ---- Helper functions ----
byte decToBcd(byte val) { return ((val / 10 * 16) + (val % 10)); }
byte bcdToDec(byte val) { return ((val / 16 * 10) + (val % 16)); }