How can we change the default setting of gyro and accelerometer sensitivity?

Using Arduino Sensors
1

Hi..
The default is setting for accelerometer is +/-2G and for gyro is +/-250deg/sec. So what are the changes one should make in mpu6050.cpp and mpu6050.h to change default setting?

thanks in advanced.

2 
MPU6050::MPU6050(PinName sda, PinName scl) : connection(sda, scl) {
    this->setSleepMode(false);
    
    //Initializations:
    currentGyroRange = 0;
    currentAcceleroRange=0;
}

I would think that if you change currentGyorRange and currentAcceloRange, in MPU6050.cpp, according to

#define MPU6050_ACCELERO_RANGE_2G   0
#define MPU6050_ACCELERO_RANGE_4G   1
#define MPU6050_ACCELERO_RANGE_8G   2
#define MPU6050_ACCELERO_RANGE_16G  3
 
#define MPU6050_GYRO_RANGE_250      0
#define MPU6050_GYRO_RANGE_500      1
#define MPU6050_GYRO_RANGE_1000     2
#define MPU6050_GYRO_RANGE_2000     3

That would change the default.

3

Since, i an new to arduino, it would be great if you just tell me where should i put the code that you have mentioned.

Here is my code:

#include "I2Cdev.h"
#include "MPU6050.h"
#include "Wire.h"
MPU6050 accelgyro;
int16_t ax, ay, az;
int16_t gx, gy, gz;
#define OUTPUT_READABLE_ACCELGYRO
#define LED_PIN 13
bool blinkState = false;
void setup() {
    
        Wire.begin();
    Serial.begin(38400);
    accelgyro.initialize();
    pinMode(LED_PIN, OUTPUT);
}

unsigned long timer;
void loop() {
    accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
     if((millis() - timer) > 8) // 100Hz
    {
      timer = millis();
      Serial.print(timer);Serial.print("\t");
      // int start=millis();Serial.print(start);Serial.print("\t");
        Serial.print(ax); Serial.print("\t");
        Serial.print(ay); Serial.print("\t");
        Serial.print(az); Serial.print("\t");
        Serial.print(gx); Serial.print("\t");
        Serial.print(gy); Serial.print("\t");
        Serial.println(gz);
    blinkState = !blinkState;
    digitalWrite(LED_PIN, blinkState);
}
}
4 
void setup() {
    
    Wire.begin();
    Serial.begin(38400);
    accelgyro.initialize();

    setFullScaleGyroRange(MPU6050_GYRO_FS_250);  
    setFullScaleAccelRange(MPU6050_ACCEL_FS_2);  

    pinMode(LED_PIN, OUTPUT);
}

#define MPU6050_ACCEL_FS_2 0x00
#define MPU6050_ACCEL_FS_4 0x01
#define MPU6050_ACCEL_FS_8 0x02
#define MPU6050_ACCEL_FS_16 0x03

#define MPU6050_GYRO_FS_250 0x00
#define MPU6050_GYRO_FS_500 0x01
#define MPU6050_GYRO_FS_1000 0x02
#define MPU6050_GYRO_FS_2000 0x03
5

Hi...
Thank you so much for your reply. Now i think its working fine. Here is the code:

#include "I2Cdev.h"
#include "MPU6050.h"
#include "Wire.h"
MPU6050 accelgyro;
int16_t ax, ay, az;
int16_t gx, gy, gz;
#define OUTPUT_READABLE_ACCELGYRO
#define LED_PIN 13
#define MPU6050_ACCEL_FS_2 0x00
#define MPU6050_ACCEL_FS_4 0x01
#define MPU6050_ACCEL_FS_8 0x02
#define MPU6050_ACCEL_FS_16 0x03

#define MPU6050_GYRO_FS_250 0x00
#define MPU6050_GYRO_FS_500 0x01
#define MPU6050_GYRO_FS_1000 0x02
#define MPU6050_GYRO_FS_2000 0x03
bool blinkState = false;
void setup() {
    
        Wire.begin();
    Serial.begin(38400);
    accelgyro.initialize();
    int setFullScaleGyroRange(MPU6050_GYRO_FS_2000);  
    int setFullScaleAccelRange(MPU6050_ACCEL_FS_2);  
    pinMode(LED_PIN, OUTPUT);
}

unsigned long timer;
void loop() {
    accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
     if((millis() - timer) > 8) // 100Hz
    {
      timer = millis();
      Serial.print(timer);Serial.print("\t");
      // int start=millis();Serial.print(start);Serial.print("\t");
        Serial.print(ax); Serial.print("\t");
        Serial.print(ay); Serial.print("\t");
        Serial.print(az); Serial.print("\t");
        Serial.print(gx); Serial.print("\t");
        Serial.print(gy); Serial.print("\t");
        Serial.println(gz);
    blinkState = !blinkState;
    digitalWrite(LED_PIN, blinkState);
}
}

Just wanted to clarify that even though we change the full scale range, the values of sensor remains the same. The only change is now in sensitivity scaling factor. Right?

6

The accel will work like that because when you change the range you are changing the number of bits in the result, the scaling is automatically set for all ranges, I am not sure about the gyro. It has been a while since I used the gyro. Edit: Can you post a link to the MPU6050 datasheet (that you have) so that I know that we are talking about the same part(s).

7

Here is a link for datasheet.
http://www.invensense.com/mems/gyro/documents/PS-MPU-6000A-00v3.4.pdf

I want to change a gyro sensitivity from 250 to 2000 deg/sec.
I observed that the serial monitor output is remain the same. It varies from -32768 to 32768.
so for sensitivity of 250 deg/sec: scaling factor is 250/32768
and for sensitivity of 2000 deg/sec: scaling factor is 2000/32768

Right?

8

Right. I may have been wrong about the a acell gain. You probably have to set the scaling according to range. Check the data sheet.

9