Hey guys, I am trying to read the angles from a mpu6050 gyroscope and accelerometer module.
I took this code from the internet
///////////////////////////////////////////////////////////////////////////////////////
//THIS IS A DEMO SOFTWARE JUST FOR EXPERIMENT PURPOER IN A NONCOMERTIAL ACTIVITY
//Version: 1.0 (AUG, 2016)
//Gyro - Arduino UNO R3
//VCC - 5V
//GND - GND
//SDA - A4
//SCL - A5
//INT - port-2
#include <Wire.h>
//Declaring some global variables
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;
long loop_timer;
int temp;
void setup() {
Wire.begin(); //Start I2C as master
setup_mpu_6050_registers(); //Setup the registers of the MPU-6050
for (int cal_int = 0; cal_int < 1000 ; cal_int ++){ //Read the raw acc and gyro data from the MPU-6050 for 1000 times
read_mpu_6050_data();
gyro_x_cal += gyro_x; //Add the gyro x offset to the gyro_x_cal variable
gyro_y_cal += gyro_y; //Add the gyro y offset to the gyro_y_cal variable
gyro_z_cal += gyro_z; //Add the gyro z offset to the gyro_z_cal variable
delay(3); //Delay 3us to have 250Hz for-loop
}
// divide by 1000 to get avarage offset
gyro_x_cal /= 1000;
gyro_y_cal /= 1000;
gyro_z_cal /= 1000;
Serial.begin(115200);
loop_timer = micros(); //Reset the loop timer
}
void loop(){
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)
angle_pitch += gyro_x * 0.0000611; //Calculate the traveled pitch angle and add this to the angle_pitch variable
angle_roll += gyro_y * 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_pitch += angle_roll * sin(gyro_z * 0.000001066); //If the IMU has yawed transfer the roll angle to the pitch angel
angle_roll -= angle_pitch * sin(gyro_z * 0.000001066); //If the IMU has yawed transfer the pitch angle to the roll angel
//Accelerometer angle calculations
acc_total_vector = sqrt((acc_x*acc_x)+(acc_y*acc_y)+(acc_z*acc_z)); //Calculate the total accelerometer vector
//57.296 = 1 / (3.142 / 180) The Arduino asin function is in radians
angle_pitch_acc = asin((float)acc_y/acc_total_vector)* 57.296; //Calculate the pitch angle
angle_roll_acc = asin((float)acc_x/acc_total_vector)* -57.296; //Calculate the roll angle
angle_pitch_acc -= 0.0; //Accelerometer calibration value for pitch
angle_roll_acc -= 0.0; //Accelerometer calibration value for roll
if(set_gyro_angles){ //If the IMU is already started
angle_pitch = angle_pitch * 0.9996 + angle_pitch_acc * 0.0004; //Correct the drift of the gyro pitch angle with the accelerometer pitch angle
angle_roll = angle_roll * 0.9996 + angle_roll_acc * 0.0004; //Correct the drift of the gyro roll angle with the accelerometer roll angle
}
else{ //At first start
angle_pitch = angle_pitch_acc; //Set the gyro pitch angle equal to the accelerometer pitch angle
angle_roll = angle_roll_acc; //Set the gyro roll angle equal to the accelerometer roll angle
set_gyro_angles = true; //Set the IMU started flag
}
//To dampen the pitch and roll angles a complementary filter is used
angle_pitch_output = angle_pitch_output * 0.9 + angle_pitch * 0.1; //Take 90% of the output pitch value and add 10% of the raw pitch value
angle_roll_output = angle_roll_output * 0.9 + angle_roll * 0.1; //Take 90% of the output roll value and add 10% of the raw roll value
Serial.print(" | Angle = "); Serial.println(angle_pitch_output);
while(micros() - loop_timer < 4000); //Wait until the loop_timer reaches 4000us (250Hz) before starting the next loop
loop_timer = micros();//Reset the loop timer
}
void setup_mpu_6050_registers(){
//Activate the MPU-6050
Wire.beginTransmission(0x68); //Start communicating with the MPU-6050
Wire.write(0x6B); //Send the requested starting register
Wire.write(0x00); //Set the requested starting register
Wire.endTransmission();
//Configure the accelerometer (+/-8g)
Wire.beginTransmission(0x68); //Start communicating with the MPU-6050
Wire.write(0x1C); //Send the requested starting register
Wire.write(0x10); //Set the requested starting register
Wire.endTransmission();
//Configure the gyro (500dps full scale)
Wire.beginTransmission(0x68); //Start communicating with the MPU-6050
Wire.write(0x1B); //Send the requested starting register
Wire.write(0x08); //Set the requested starting register
Wire.endTransmission();
}
void read_mpu_6050_data(){ //Subroutine for reading the raw gyro and accelerometer data
Wire.beginTransmission(0x68); //Start communicating with the MPU-6050
Wire.write(0x3B); //Send the requested starting register
Wire.endTransmission(); //End the transmission
Wire.requestFrom(0x68,14); //Request 14 bytes from the MPU-6050
while(Wire.available() < 14); //Wait until all the bytes are received
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();
}
When the serial communication baud rate is 115200, the output works perfectly.
If i change it to 9600, the output range becomes half.
I think it has something to do with the loop timer(which i dont understand its purpose).
Can someone help.
Thanks.
EDIT:
I did some experimenting with the code. It dosen't work properly if i add in any delay or try to change something which has something to do with the 250 hertz loop. I think the loop is responsible to keep the values correct. If someone could explain it i would be able to make changes to it. Thanks.