Hi, i am trying to calibrate my MPU-6050 and GY-271 (magnetometer) for use in an AHRS.
Here is the code i used to find the offsets for the MPU-6050:
// 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.
// Code website: http://wired.chillibasket.com/2015/01/calibrating-mpu6050/
/* ========== ====== ==================================
NOTE: In addition to connection 3.3v, GND, SDA, and SCL, For this
connect the pin labelled as SDA on the MPU 6050
to the arduino’s (A4) analog pin 4 (SDA). And the pin labelled as SCL on the MPU
6050 to the arduino’s (A5) analog pin 5 (SCL).
=========================================================
*/
// 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();
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;
}
}
I uploaded the code and it gave me some offsets for the accelerometer and gyroscope, which i then used in my own code here:
mpu.setXAccelOffset(-2333);
mpu.setYAccelOffset(371);
mpu.setZAccelOffset(5050);
mpu.setXGyroOffset(114);
mpu.setYGyroOffset(-30);
mpu.setZGyroOffset(-5);
Here are the offset gyroscope readings:
Gyro: X,Y,Z -0.02, -0.15, -0.24
Gyro: X,Y,Z 0.09, -0.11, -0.37
Gyro: X,Y,Z -0.01, -0.02, -0.21
Gyro: X,Y,Z 0.02, 0.02, -0.14
Gyro: X,Y,Z 0.18, 0.08, -0.18
Gyro: X,Y,Z 0.06, -0.08, -0.44
Gyro: X,Y,Z 0.17, 0.02, -0.28
Gyro: X,Y,Z 0.07, -0.05, -0.25
Gyro: X,Y,Z -0.16, 0.11, -0.31
Gyro: X,Y,Z 0.00, 0.08, -0.41
Gyro: X,Y,Z -0.12, 0.01, -0.29
Gyro: X,Y,Z 0.20, -0.02, -0.43
Gyro: X,Y,Z 0.28, 0.07, -0.25
Gyro: X,Y,Z 0.00, -0.13, -0.37
Gyro: X,Y,Z 0.05, 0.04, -0.29
Gyro: X,Y,Z -0.06, 0.01, -0.58
Gyro: X,Y,Z -0.09, -0.08, -0.40
Gyro: X,Y,Z -0.15, -0.18, -0.30
Gyro: X,Y,Z -0.04, -0.01, -0.28
Gyro: X,Y,Z -0.10, -0.15, -0.42
Gyro: X,Y,Z -0.02, -0.02, -0.41
Gyro: X,Y,Z -0.02, 0.15, -0.44
Gyro: X,Y,Z 0.05, 0.18, -0.25
Gyro: X,Y,Z -0.07, -0.04, -0.23
Gyro: X,Y,Z -0.09, -0.10, -0.33
Gyro: X,Y,Z 0.01, -0.06, -0.42
Gyro: X,Y,Z -0.10, 0.08, -0.43
Gyro: X,Y,Z 0.01, -0.14, -0.43
Gyro: X,Y,Z 0.06, 0.00, -0.34
Gyro: X,Y,Z 0.08, -0.16, -0.51
Gyro: X,Y,Z 0.01, 0.05, -0.62
Gyro: X,Y,Z 0.01, -0.06, -0.49
Gyro: X,Y,Z -0.02, 0.15, -0.41
Do these look correct? I know that the offset gyro readings should about 0 but in some instances the readings are going all the way up to +-0.6. Is this normal? Or did i do something wrong?
I have attached the graph plots of the offset gyroscope readings along with the non-offset gyroscope readings.
