B4R Question mpu6050 calibration: setXAccelOffset

peacemaker

Expert
Licensed User
Hi, All
If there is such Arduino sketch code:
B4X:
// 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(115200);

  // 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;
  }
}

How can be used
setXAccelOffset
setYAccelOffset
setZAccelOffset
in B4R for ESP8266 ?

Only these functions are interesting, other calculations can be prepared by B4R without inline-C.
 

peacemaker

Expert
Licensed User
Erel, but what should be start in inline-C here ? Starting from connecting by I2C ?
I mean i have to disconnect firstly my B4R code, and make full reconnection by inline-C ?
 

peacemaker

Expert
Licensed User
Sorry, but i do not understand how to initialize the object in inline-C that to use only setAccel methods, to make shortest inline-C part.
I mean - how to combine the connection to I2C and lib object initialization to use its methods ?
 
Last edited:

derez

Expert
Licensed User
To get the parameters in inline C you'll have to follow the calibration process in the code above, not just read the parameters.
You can do a similar process in B4R: while the board is on a table make many measurements of all parameters (discarding the first as the code above does), then keep the mean value of each parameter as the offset, reducing it later on from every measurement done while the board is in movement.
 

peacemaker

Expert
Licensed User
All about reading data is already done. Now task is "just" write the calibration deltas into the IC.
 
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