MPU9150 output is weird

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1

Hey, I’m doing my final year project and this is what I got for the output of MPU9150 for accelerometer and gyro.

These are the raw data.

DATA               
X_acc   Y_acc   Z_acc   X_gyro   Y_gyro   Z_gyro
416   -16   -16916   -225   4   161
360   120   -16868   -216   -254   124
480   -44   -16688   -226   -17   165
372   -12   -16996   -229   248   129
296   -48   -16872   -510   -2   139
292   -88   -16644   -265   -7   154
304   20   -16788   -223   -36   146
388   -52   -16864   -244   -1   135
376   12   -16892   -226   -1   116
340   -164   -16832   -228   -7   149
408   -256   -16996   -226   0   176
360   48   -16904   -227   15   144
392   32   -16900   -251   -5   143
376   -220   -16884   -250   -28   145
304   -76   -16892   -254   -12   112
452   -40   -17128   -511   255   133
344   36   -16716   -243   1   135
356   -112   -17008   -253   13   132
316   -52   -16676   -201   15   141
364   -172   -16964   -238   -8   134
320   -80   -16856   -243   -7   146
356   -36   -16816   -200   -35   154
384   -112   -17016   -235   -4   144
396   -24   -16900   -212   -42   138
264   -168   -16856   -208   -18   123
300   -492   -16788   -226   -33   156
388   -36   -16820   -214   -29   153
388   -24   -16688   -208   -16   148
344   -20   -16720   -236   5   135
412   -40   -16836   -217   255   147
392   -92   -16980   -235   243   127
452   -24   -16904   -240   -15   158
372   -108   -16852   -226   -11   128
392   -36   -16848   -232   -2   136
436   -20   -16904   -223   -22   140
400   24   -16988   -226   2   141
448   -240   -16876   -242   -256   105
452   -4   -16784   -243   -22   159
380   -28   -16856   -201   -4   138
376   12   -16980   -216   -14   161
340   -24   -16720   -2   -10   119
300   24   -16944   -213   7   110
408   -24   -16744   -234   -24   143
160   -284   -16812   -2   -20   146
748   144   -16856   -214   -18   147
332   -428   -16972   -219   3   162

and I convert it by divide these raw data with 16384 for accelerometer raw data and divide with 131 for gyro raw data. (scale that i used was 2g and 250deg/sec). these are what i got.

ACCELERATION         ANGULAR ACCELERATION      
X_acc   Y_acc   Z_acc   X_gyro   Y_gyro   Z_gyro
0.025390625   -0.000976563   -1.032470703   -1.717557252   0.030534351   1.229007634
0.021972656   0.007324219   -1.029541016   -1.648854962   -1.938931298   0.946564885
0.029296875   -0.002685547   -1.018554688   -1.72519084   -0.129770992   1.259541985
0.022705078   -0.000732422   -1.037353516   -1.748091603   1.893129771   0.984732824
0.018066406   -0.002929688   -1.029785156   -3.893129771   -0.015267176   1.061068702
0.017822266   -0.005371094   -1.015869141   -2.022900763   -0.053435115   1.175572519
0.018554688   0.001220703   -1.024658203   -1.702290076   -0.27480916   1.114503817
0.023681641   -0.003173828   -1.029296875   -1.86259542   -0.007633588   1.030534351
0.022949219   0.000732422   -1.031005859   -1.72519084   -0.007633588   0.885496183
0.020751953   -0.010009766   -1.02734375   -1.740458015   -0.053435115   1.13740458
0.024902344   -0.015625   -1.037353516   -1.72519084   0   1.34351145
0.021972656   0.002929688   -1.031738281   -1.732824427   0.114503817   1.099236641
0.023925781   0.001953125   -1.031494141   -1.916030534   -0.038167939   1.091603053
0.022949219   -0.013427734   -1.030517578   -1.908396947   -0.213740458   1.106870229
0.018554688   -0.004638672   -1.031005859   -1.938931298   -0.091603053   0.854961832
0.027587891   -0.002441406   -1.045410156   -3.900763359   1.946564885   1.015267176
0.020996094   0.002197266   -1.020263672   -1.854961832   0.007633588   1.030534351
0.021728516   -0.006835938   -1.038085938   -1.93129771   0.099236641   1.007633588
0.019287109   -0.003173828   -1.017822266   -1.534351145   0.114503817   1.076335878
0.022216797   -0.010498047   -1.035400391   -1.816793893   -0.061068702   1.022900763
0.01953125   -0.004882813   -1.028808594   -1.854961832   -0.053435115   1.114503817
0.021728516   -0.002197266   -1.026367188   -1.526717557   -0.267175573   1.175572519
0.0234375   -0.006835938   -1.038574219   -1.79389313   -0.030534351   1.099236641
0.024169922   -0.001464844   -1.031494141   -1.618320611   -0.320610687   1.053435115
0.016113281   -0.010253906   -1.028808594   -1.58778626   -0.13740458   0.938931298
0.018310547   -0.030029297   -1.024658203   -1.72519084   -0.251908397   1.190839695
0.023681641   -0.002197266   -1.026611328   -1.633587786   -0.221374046   1.167938931
0.023681641   -0.001464844   -1.018554688   -1.58778626   -0.122137405   1.129770992
0.020996094   -0.001220703   -1.020507813   -1.801526718   0.038167939   1.030534351
0.025146484   -0.002441406   -1.027587891   -1.65648855   1.946564885   1.122137405
0.023925781   -0.005615234   -1.036376953   -1.79389313   1.854961832   0.969465649
0.027587891   -0.001464844   -1.031738281   -1.832061069   -0.114503817   1.20610687
0.022705078   -0.006591797   -1.028564453   -1.72519084   -0.083969466   0.977099237
0.023925781   -0.002197266   -1.028320313   -1.770992366   -0.015267176   1.038167939
0.026611328   -0.001220703   -1.031738281   -1.702290076   -0.167938931   1.06870229
0.024414063   0.001464844   -1.036865234   -1.72519084   0.015267176   1.076335878
0.02734375   -0.014648438   -1.030029297   -1.847328244   -1.954198473   0.801526718
0.027587891   -0.000244141   -1.024414063   -1.854961832   -0.167938931   1.213740458
0.023193359   -0.001708984   -1.028808594   -1.534351145   -0.030534351   1.053435115
0.022949219   0.000732422   -1.036376953   -1.648854962   -0.106870229   1.229007634
0.020751953   -0.001464844   -1.020507813   -0.015267176   -0.076335878   0.908396947
0.018310547   0.001464844   -1.034179688   -1.625954198   0.053435115   0.839694656
0.024902344   -0.001464844   -1.021972656   -1.786259542   -0.183206107   1.091603053
0.009765625   -0.017333984   -1.026123047   -0.015267176   -0.152671756   1.114503817
0.045654297   0.008789063   -1.028808594   -1.633587786   -0.13740458   1.122137405
0.020263672   -0.026123047   -1.035888672   -1.671755725   0.022900763   1.236641221

the MPU9150 was put is a static place but how can the gyro reading didnt become 0?

can anybody teach me please!

2

Output OFFSET ERROR. You need to calibrate the Gyro and the accel for offset errors then subtract these from the raw readings. There could also be noise getting into the chip that is causing the variations in the readings since just an offset error does not explain why the accel and gyro readings are not near constant. Do you have adequate ceramic de-coupling caps very close the each pair of Vdd & Vss pins?

3

The data sheet clearly specifies that the gyro zero offset can be anywhere in the range of +/-20 d/sec.

4

Because the noise spikes have a magnitude of about 256 counts, I suspect that you have overlooked this paragraph from the data sheet:

The data within the gyroscope sensors’ internal register set is always updated at the Sample Rate. Meanwhile, the user-facing read register set duplicates the internal register set’s data values whenever the serial interface is idle. This guarantees that a burst read of sensor registers will read measurements from the same sampling instant. Note that if burst reads are not used, the user is responsible for ensuring a set of single byte reads correspond to a single sampling instant by checking the Data Ready interrupt.