Only z-acceleration incorrect

[YasinnnA]

Hello community,

I hope it's okay if I ask a question about my project here. I'm encountering an false value in my z acceleration when I rotate the MPU 180 degrees. This issue is specific to the Z acceleration. Normally, it should result in approximately 0 (instead of 14800).

I hope someone can help me.

Best regards

Output:

accX: 56  accY: -32  accZ: 16320
accX: 92  accY: -32  accZ: 16372
accX: 4  accY: -140  accZ: 16320
accX: -76  accY: -64  accZ: 16380
accX: 8672  accY: 164  accZ: 16056
accX: 16016  accY: -72  accZ: 15216
accX: 16104  accY: -368  accZ: 14940
accX: 16160  accY: -544  accZ: 14904
accX: 16132  accY: -440  accZ: 14824

Code:

#include <unistd.h> 
#include "MPU6050.h"
#include "stdio.h"
#include "I2Cdev.h"
#include <iostream>

MPU6050 accelgyro(0x68);

int16_t ax, ay, az, ox, oy, oz;
float  dax, day, daz,dox, doy, doz;


void setup()
{
    I2Cdev i2cDevice(2); 
    accelgyro.initialize();


// ....................    XAccel                  YAccel                          ZAccel                  XGyro                   YGyro                   ZGyro
//                      [-31,-30] --> [-13,3]      [3839,3841] --> [-14,2] [1929,1930] --> [16375,16402]   [174,175] --> [-2,1]    [240,241] --> [-3,1]    [41,42] --> [0,4]
// .................... [-31,-30] --> [-11,3]      [3839,3840] --> [-14,1] [1929,1930] --> [16383,16402]   [174,175] --> [-3,1]    [240,241] --> [-3,1]    [41,42] --> [-1,4]
// .................... [-31,-30] --> [-9,3]       [3839,3840] --> [-19,1] [1929,1930] --> [16381,16402]   [174,175] --> [-2,1]    [240,241] --> [-3,1]    [41,42] --> [0,4]
// -------------- done --------------

    accelgyro.setXAccelOffset(-31);
    accelgyro.setYAccelOffset(3839);
    accelgyro.setZAccelOffset(1929);
    
        printf("Offset:");
        printf("%i \t %i \t %i \t %i \t %i \t %i\n", 
	 accelgyro.getXAccelOffset(),
	 accelgyro.getYAccelOffset(),
	 accelgyro.getZAccelOffset(),
	 accelgyro.getXGyroOffset(),
	 accelgyro.getYGyroOffset(),
	 accelgyro.getZGyroOffset());
}

int main() {  

    setup();    

    while (true)
    {

        accelgyro.getAcceleration(&ax,&ay,&az);
        printf("accX: %d  accY: %d  accZ: %d \n",ax,ay, az);
        usleep(500* 1000);


    }
    

	return 0;


}

[jrowberg]

Hello @YasinnnA,

That's pretty significant. Does the raw Z accel data ever go outside of that range, e.g. if you flip the IMU upside-down? There's a possibility that you have a faulty device, but that's most easily checked by swapping in a different one. Do you happen to have another one available to test with?

[YasinnnA]

Hello @jrowberg,

Thank you so much! I checked it today with a new MPU, and it worked.
Cheers!