mpu6050 electronic level

/*
  Electronic Level
  mpu-6050-level.ino
  Uses MPU-6050 IMU
  Displays on 128x64 OLED and LED

  DroneBot Workshop 2019
  https://dronebotworkshop.com
*/

// Include Wire Library for I2C
#include <Wire.h>

// Include NewLiquidCrystal Library for I2C
#include <LiquidCrystal_I2C.h>

// Define LCD pinout
const int  en = 2, rw = 1, rs = 0, d4 = 4, d5 = 5, d6 = 6, d7 = 7, bl = 3;

// Define I2C Address - change if reqiuired
const int i2c_addr = 0x3F;

LiquidCrystal_I2C lcd(i2c_addr, en, rw, rs, d4, d5, d6, d7, bl, POSITIVE);

// Level LEDs
int levelLED_neg1 = 9;
int levelLED_neg0 = 10;
int levelLED_level = 11;
int levelLED_pos0 = 12;
int levelLED_pos1 = 13;



//Variables for Gyroscope
int gyro_x, gyro_y, gyro_z;
long gyro_x_cal, gyro_y_cal, gyro_z_cal;
boolean set_gyro_angles;

long acc_x, acc_y, acc_z, acc_total_vector;
float angle_roll_acc, angle_pitch_acc;

float angle_pitch, angle_roll;
int angle_pitch_buffer, angle_roll_buffer;
float angle_pitch_output, angle_roll_output;

// Setup timers and temp variables
long loop_timer;
int temp;

// Display counter
int displaycount = 0;

void setup() {

  //Start I2C
  Wire.begin();

  // Set display type as 16 char, 2 rows
  lcd.begin(16,2);

  // Set Level LEDs as outputs
  pinMode(levelLED_neg1, OUTPUT);
  pinMode(levelLED_neg0, OUTPUT);
  pinMode(levelLED_level, OUTPUT);
  pinMode(levelLED_pos0, OUTPUT);
  pinMode(levelLED_pos1, OUTPUT);


  //Setup the registers of the MPU-6050
  setup_mpu_6050_registers();

  //Read the raw acc and gyro data from the MPU-6050 1000 times
  for (int cal_int = 0; cal_int < 1000 ; cal_int ++){
    read_mpu_6050_data();
    //Add the gyro x offset to the gyro_x_cal variable
    gyro_x_cal += gyro_x;
    //Add the gyro y offset to the gyro_y_cal variable
    gyro_y_cal += gyro_y;
    //Add the gyro z offset to the gyro_z_cal variable
    gyro_z_cal += gyro_z;
    //Delay 3us to have 250Hz for-loop
    delay(3);
  }

  // Divide all results by 1000 to get average offset
  gyro_x_cal /= 1000;
  gyro_y_cal /= 1000;
  gyro_z_cal /= 1000;

  // Start Serial Monitor
  Serial.begin(115200);

  // Init Timer
  loop_timer = micros();
}

void loop(){

  // Get data from MPU-6050
  read_mpu_6050_data();

  //Subtract the offset values from the raw gyro values
  gyro_x -= gyro_x_cal;
  gyro_y -= gyro_y_cal;
  gyro_z -= gyro_z_cal;

  //Gyro angle calculations . Note 0.0000611 = 1 / (250Hz x 65.5)

  //Calculate the traveled pitch angle and add this to the angle_pitch variable
  angle_pitch += gyro_x * 0.0000611;
  //Calculate the traveled roll angle and add this to the angle_roll variable
  //0.000001066 = 0.0000611 * (3.142(PI) / 180degr) The Arduino sin function is in radians
  angle_roll += gyro_y * 0.0000611;

  //If the IMU has yawed transfer the roll angle to the pitch angle
  angle_pitch += angle_roll * sin(gyro_z * 0.000001066);
  //If the IMU has yawed transfer the pitch angle to the roll angle
  angle_roll -= angle_pitch * sin(gyro_z * 0.000001066);

  //Accelerometer angle calculations

  //Calculate the total accelerometer vector
  acc_total_vector = sqrt((acc_x*acc_x)+(acc_y*acc_y)+(acc_z*acc_z));

  //57.296 = 1 / (3.142 / 180) The Arduino asin function is in radians
  //Calculate the pitch angle
  angle_pitch_acc = asin((float)acc_y/acc_total_vector)* 57.296;
  //Calculate the roll angle
  angle_roll_acc = asin((float)acc_x/acc_total_vector)* -57.296;

  //Accelerometer calibration value for pitch
  angle_pitch_acc -= 0.0;
  //Accelerometer calibration value for roll
  angle_roll_acc -= 0.0;

  if(set_gyro_angles){

  //If the IMU has been running
  //Correct the drift of the gyro pitch angle with the accelerometer pitch angle
    angle_pitch = angle_pitch * 0.9996 + angle_pitch_acc * 0.0004;
    //Correct the drift of the gyro roll angle with the accelerometer roll angle
    angle_roll = angle_roll * 0.9996 + angle_roll_acc * 0.0004;
  }
  else{
    //IMU has just started
    //Set the gyro pitch angle equal to the accelerometer pitch angle
    angle_pitch = angle_pitch_acc;
    //Set the gyro roll angle equal to the accelerometer roll angle
    angle_roll = angle_roll_acc;
    //Set the IMU started flag
    set_gyro_angles = true;
  }

  //To dampen the pitch and roll angles a complementary filter is used
  //Take 90% of the output pitch value and add 10% of the raw pitch value
  angle_pitch_output = angle_pitch_output * 0.9 + angle_pitch * 0.1;
  //Take 90% of the output roll value and add 10% of the raw roll value
  angle_roll_output = angle_roll_output * 0.9 + angle_roll * 0.1;
  //Wait until the loop_timer reaches 4000us (250Hz) before starting the next loop

  // Print to Serial Monitor
  //Serial.print(" | Angle  = "); Serial.println(angle_pitch_output);


  // Increment the display counter
  displaycount = displaycount +1;

  if (displaycount > 100) {

  lcd.clear();
  // Print on first row of LCD
  lcd.setCursor(0,0);
  lcd.print("Pitch: ");
  lcd.print(angle_pitch_output);
  lcd.setCursor(0,1);
  lcd.print("Roll: ");
  lcd.print(angle_roll_output);


  // Check Angle for Level LEDs

    if (angle_pitch_output < -2.01) {
    // Turn on Level LED
    digitalWrite(levelLED_neg1, HIGH);
    digitalWrite(levelLED_neg0, LOW);
    digitalWrite(levelLED_level, LOW);
    digitalWrite(levelLED_pos0, LOW);
    digitalWrite(levelLED_pos1, LOW);

    } else if ((angle_pitch_output > -2.00) && (angle_pitch_output < -1.01)) {
    // Turn on Level LED
    digitalWrite(levelLED_neg1, LOW);
    digitalWrite(levelLED_neg0, HIGH);
    digitalWrite(levelLED_level, LOW);
    digitalWrite(levelLED_pos0, LOW);
    digitalWrite(levelLED_pos1, LOW);

    } else if ((angle_pitch_output < 1.00) && (angle_pitch_output > -1.00)) {
    // Turn on Level LED
    digitalWrite(levelLED_neg1, LOW);
    digitalWrite(levelLED_neg0, LOW);
    digitalWrite(levelLED_level, HIGH);
    digitalWrite(levelLED_pos0, LOW);
    digitalWrite(levelLED_pos1, LOW);

    } else if ((angle_pitch_output > 1.01) && (angle_pitch_output < 2.00)) {
    // Turn on Level LED
    digitalWrite(levelLED_neg1, LOW);
    digitalWrite(levelLED_neg0, LOW);
    digitalWrite(levelLED_level, LOW);
    digitalWrite(levelLED_pos0, HIGH);
    digitalWrite(levelLED_pos1, LOW);

    } else if (angle_pitch_output > 2.01) {
    // Turn on Level LED
    digitalWrite(levelLED_neg1, LOW);
    digitalWrite(levelLED_neg0, LOW);
    digitalWrite(levelLED_level, LOW);
    digitalWrite(levelLED_pos0, LOW);
    digitalWrite(levelLED_pos1, HIGH);

    }

  displaycount = 0;

  }


 while(micros() - loop_timer < 4000);
 //Reset the loop timer
 loop_timer = micros();

}

void setup_mpu_6050_registers(){

  //Activate the MPU-6050

  //Start communicating with the MPU-6050
  Wire.beginTransmission(0x68);
  //Send the requested starting register
  Wire.write(0x6B);
  //Set the requested starting register
  Wire.write(0x00);
  //End the transmission
  Wire.endTransmission();

  //Configure the accelerometer (+/-8g)

  //Start communicating with the MPU-6050
  Wire.beginTransmission(0x68);
  //Send the requested starting register
  Wire.write(0x1C);
  //Set the requested starting register
  Wire.write(0x10);
  //End the transmission
  Wire.endTransmission();

  //Configure the gyro (500dps full scale)

  //Start communicating with the MPU-6050
  Wire.beginTransmission(0x68);
  //Send the requested starting register
  Wire.write(0x1B);
  //Set the requested starting register
  Wire.write(0x08);
  //End the transmission
  Wire.endTransmission();

}


void read_mpu_6050_data(){

  //Read the raw gyro and accelerometer data

  //Start communicating with the MPU-6050
  Wire.beginTransmission(0x68);
  //Send the requested starting register
  Wire.write(0x3B);
  //End the transmission
  Wire.endTransmission();
  //Request 14 bytes from the MPU-6050
  Wire.requestFrom(0x68,14);
  //Wait until all the bytes are received
  while(Wire.available() < 14);

  //Following statements left shift 8 bits, then bitwise OR.
  //Turns two 8-bit values into one 16-bit value
  acc_x = Wire.read()<<8|Wire.read();
  acc_y = Wire.read()<<8|Wire.read();
  acc_z = Wire.read()<<8|Wire.read();
  temp = Wire.read()<<8|Wire.read();
  gyro_x = Wire.read()<<8|Wire.read();
  gyro_y = Wire.read()<<8|Wire.read();
  gyro_z = Wire.read()<<8|Wire.read();
}