Auto-Calibration MPU6050

//MPU6050 Auto-Calibration

// Arduino sketch that returns calibration offsets for MPU6050 

//   Version 1.1  (31th January 2014)

// Done by Luis Ródenas <luisrodenaslorda@gmail.com>

// Based on the I2Cdev library and previous work by Jeff Rowberg <jeff@rowberg.net>

// Updates (of the library) should (hopefully) always be available at https://github.com/jrowberg/i2cdevlib

// These offsets were meant to calibrate MPU6050's internal DMP, but can be also useful for reading sensors. 

// The effect of temperature has not been taken into account so I can't promise that it will work if you 

// calibrate indoors and then use it outdoors. Best is to calibrate and use at the same room temperature.

/* ==========  LICENSE  ==================================

 I2Cdev device library code is placed under the MIT license

 Copyright (c) 2011 Jeff Rowberg

 Permission is hereby granted, free of charge, to any person obtaining a copy

 of this software and associated documentation files (the "Software"), to deal

 in the Software without restriction, including without limitation the rights

 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 copies of the Software, and to permit persons to whom the Software is

 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in

 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 THE SOFTWARE.

 =========================================================

 */

// I2Cdev and MPU6050 must be installed as libraries

#include "I2Cdev.h"

#include "MPU6050.h"

#include "Wire.h"

///////////////////////////////////   CONFIGURATION   /////////////////////////////

//Change this 3 variables if you want to fine tune the skecth to your needs.

int buffersize=1000;     //Amount of readings used to average, make it higher to get more precision but sketch will be slower  (default:1000)

int acel_deadzone=8;     //Acelerometer error allowed, make it lower to get more precision, but sketch may not converge  (default:8)

int giro_deadzone=1;     //Giro error allowed, make it lower to get more precision, but sketch may not converge  (default:1)

// default I2C address is 0x68

// specific I2C addresses may be passed as a parameter here

// AD0 low = 0x68 (default for InvenSense evaluation board)

// AD0 high = 0x69

//MPU6050 accelgyro;

MPU6050 accelgyro(0x68); // <-- use for AD0 high

int16_t ax, ay, az,gx, gy, gz;

int mean_ax,mean_ay,mean_az,mean_gx,mean_gy,mean_gz,state=0;

int ax_offset,ay_offset,az_offset,gx_offset,gy_offset,gz_offset;

///////////////////////////////////   SETUP   ////////////////////////////////////

void setup() {

  // join I2C bus (I2Cdev library doesn't do this automatically)

  Wire.begin();

  // COMMENT NEXT LINE IF YOU ARE USING ARDUINO DUE

  TWBR = 24; // 400kHz I2C clock (200kHz if CPU is 8MHz). Leonardo measured 250kHz.

  // initialize serial communication

  Serial.begin(19200);

  // initialize device

  accelgyro.initialize();

  // wait for ready

  while (Serial.available() && Serial.read()); // empty buffer

  while (!Serial.available()){

    Serial.println(F("Send any character to start sketch.\n"));

    delay(1500);

  }                

  while (Serial.available() && Serial.read()); // empty buffer again

  // start message

  Serial.println("\nMPU6050 Calibration Sketch");

  delay(2000);

  Serial.println("\nYour MPU6050 should be placed in horizontal position, with package letters facing up. \nDon't touch it until you see a finish message.\n");

  delay(3000);

  // verify connection

  Serial.println(accelgyro.testConnection() ? "MPU6050 connection successful" : "MPU6050 connection failed");

  delay(1000);

  // reset offsets

  accelgyro.setXAccelOffset(0);

  accelgyro.setYAccelOffset(0);

  accelgyro.setZAccelOffset(0);

  accelgyro.setXGyroOffset(0);

  accelgyro.setYGyroOffset(0);

  accelgyro.setZGyroOffset(0);

}

///////////////////////////////////   LOOP   ////////////////////////////////////

void loop() {

  if (state==0){

    Serial.println("\nReading sensors for first time...");

    meansensors();

    state++;

    delay(1000);

  }

  if (state==1) {

    Serial.println("\nCalculating offsets...");

    calibration();

    state++;

    delay(1000);

  }

  if (state==2) {

    meansensors();

    Serial.println("\nFINISHED!");

    Serial.print("\nSensor readings with offsets:\t");

    Serial.print(mean_ax); 

    Serial.print("\t");

    Serial.print(mean_ay); 

    Serial.print("\t");

    Serial.print(mean_az); 

    Serial.print("\t");

    Serial.print(mean_gx); 

    Serial.print("\t");

    Serial.print(mean_gy); 

    Serial.print("\t");

    Serial.println(mean_gz);

    Serial.print("Your offsets:\t");

    Serial.print(ax_offset); 

    Serial.print("\t");

    Serial.print(ay_offset); 

    Serial.print("\t");

    Serial.print(az_offset); 

    Serial.print("\t");

    Serial.print(gx_offset); 

    Serial.print("\t");

    Serial.print(gy_offset); 

    Serial.print("\t");

    Serial.println(gz_offset); 

    Serial.println("\nData is printed as: acelX acelY acelZ giroX giroY giroZ");

    Serial.println("Check that your sensor readings are close to 0 0 16384 0 0 0");

    Serial.println("If calibration was succesful write down your offsets so you can set them in your projects using something similar to mpu.setXAccelOffset(youroffset)");

    while (1);

  }

}

///////////////////////////////////   FUNCTIONS   ////////////////////////////////////

void meansensors(){

  long i=0,buff_ax=0,buff_ay=0,buff_az=0,buff_gx=0,buff_gy=0,buff_gz=0;

  while (i<(buffersize+101)){

    // read raw accel/gyro measurements from device

    accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);

    if (i>100 && i<=(buffersize+100)){ //First 100 measures are discarded

      buff_ax=buff_ax+ax;

      buff_ay=buff_ay+ay;

      buff_az=buff_az+az;

      buff_gx=buff_gx+gx;

      buff_gy=buff_gy+gy;

      buff_gz=buff_gz+gz;

    }

    if (i==(buffersize+100)){

      mean_ax=buff_ax/buffersize;

      mean_ay=buff_ay/buffersize;

      mean_az=buff_az/buffersize;

      mean_gx=buff_gx/buffersize;

      mean_gy=buff_gy/buffersize;

      mean_gz=buff_gz/buffersize;

    }

    i++;

    delay(2); //Needed so we don't get repeated measures

  }

}

void calibration(){

  ax_offset=-mean_ax/8;

  ay_offset=-mean_ay/8;

  az_offset=(16384-mean_az)/8;

  gx_offset=-mean_gx/4;

  gy_offset=-mean_gy/4;

  gz_offset=-mean_gz/4;

  while (1){

    int ready=0;

    accelgyro.setXAccelOffset(ax_offset);

    accelgyro.setYAccelOffset(ay_offset);

    accelgyro.setZAccelOffset(az_offset);

    accelgyro.setXGyroOffset(gx_offset);

    accelgyro.setYGyroOffset(gy_offset);

    accelgyro.setZGyroOffset(gz_offset);

    meansensors();

    Serial.println("...");

    if (abs(mean_ax)<=acel_deadzone) ready++;

    else ax_offset=ax_offset-mean_ax/acel_deadzone;

    if (abs(mean_ay)<=acel_deadzone) ready++;

    else ay_offset=ay_offset-mean_ay/acel_deadzone;

    if (abs(16384-mean_az)<=acel_deadzone) ready++;

    else az_offset=az_offset+(16384-mean_az)/acel_deadzone;

    if (abs(mean_gx)<=giro_deadzone) ready++;

    else gx_offset=gx_offset-mean_gx/(giro_deadzone+1);

    if (abs(mean_gy)<=giro_deadzone) ready++;

    else gy_offset=gy_offset-mean_gy/(giro_deadzone+1);

    if (abs(mean_gz)<=giro_deadzone) ready++;

    else gz_offset=gz_offset-mean_gz/(giro_deadzone+1);

    if (ready==6) break;

  }

}