报告的Android随机传感器值

我正试图分析来自Galaxy Nexus的Android传感器数据，我遇到了一些奇怪的模式。例如，我得到磁场传感器的重复值8，屏幕方向传感器的随机值255。在我阅读的文档中，这些值似乎没有任何特殊意义，但它们会反复出现。有人知道为什么吗

我包括了传感器数据输出的样本，以防有人需要，0表示在监听时间段1分钟内没有返回数据。每行5分钟不同：

MPU6500 Acceleration Sensor AK09911C Magnetic field Sensor  AK09911C Magnetic Sensor UnCalibrated   MPU6500 Gyroscope Sensor    MPU6500 Uncalibrated Gyroscope Sensor   Barometer Sensor    TMG399X Proximity Sensor    TMG399X RGB Sensor  MPL Rotation Vector MPL Game Rotation Vector    SAMSUNG Step Detector Sensor    SAMSUNG Step Counter Sensor SAMSUNG Significant Motion Sensor   MAX86900    Screen Orientation Sensor   HRM Sensor  Orientation Sensor  Gravity Sensor  Linear Acceleration Sensor
-0.7918822  -1.44   8   -0.0010652645   0   0   0.027657    -0.00831    107.56043   0   0   255 0   0   -0.79049826 0.005798638 344.4021    -0.7916513  0.012937188
-1.6178818  18.66   -1.14   8   8   0   0.028444    -0.008315   0   0   0   255 0   0   -1.6365771  0.04024315  110.17886   -1.6392937  0.029791594
-1.638831   8   8   -2.66E-04   0   0.047552    -0.03045    0   0   0   255 0   0   0   -1.6823589  0.04951334  352.47757   -1.6795416  0.03173232
-1.6753427  -1.08   8   -0.0026631611   0   0.048844    -0.030235   0   1   0   255 0   0   0   -1.7105712  0.07293725  103.25511   -1.7080178  0.043449044
-1.721431   8   8   0.0013315806    0.0013315806    0.044273    -0.03007    0   0   0   255 0   0   0   -1.7184123  0.013740659 358.64462   -1.7213204  0.008867621
-1.7154455  18.72   -1.08   8   0.046393    -0.030042   0   0   0   255 0   0   0   0   -1.7471539  0.020335913 97.08981    -1.7468109  0.036153793
-1.8076223  -1.08   8   -0.0034621095   -0.0034621095   0   0.032184    -0.052209   0   0   0   255 0   0   -1.8572613  0.07178533  9.031282    -1.849128   0.043301344
-1.7962499  -1.08   8   8   -0.051598   -0.050319   1   0   0   255 0   0   0   0   -1.8097965  0.018933535 98.16796    -1.8121501  0.0069220066
-1.7830818  14.4    8   8   0   0   0.031865    -0.051793   0   0   0   0   0   255 -1.8501818  0.051537752 6.3113422   -1.8480959  0.033290982
-1.8968062  -1.02   8   8   0   0.035205    -0.051669   0   0   0   0   255 0   0   -1.9285302  0.06584132  9.900935    -1.9213988  0.02040255
-1.846528   15.06   8   8   0   0   0   88.72001    -0.0386 -1.8738624  255 0   0   0   -1.8782147  0.009540319 13.564674   -1.8787019  0.023794174
-1.2557588  18.6    8   8   0.002130529 -0.056822   -0.059393   0   0   255 0   0   1   0   -1.2829624  0.013437033 99.33356    -1.2816399  0.024684072
-1.2449849  18.6    8   0.014114754 0   0   0   85.962204   0.003289    -0.057907   -1.2985611  0   0   255 -1.2931483  0.042776465 14.364091   -1.2938662  0.037508845
-1.2443863  18.54   -1.26   8   8   0   0   -0.054567   -0.056251   2.5835018   0   0   255 0   -1.2474166  -0.011933446    93.84088    -1.2518827  -0.0062702894
-1.1426327  18.72   8   8   0   -0.052494   -0.056559   1   0   0   255 0   0   0   -1.1527904  0.017340302 6.746513    -1.1546664  0.01502645
-1.1492168  18.6    8   8   0.002396845 0   -0.048156   -0.04867    0   0   255 0   0   0   -1.1757433  0.03131497  99.13985    -1.1777196  0.019524574
-1.4927847  8   -2.66E-04   0   0   0.031505    -0.028662   0   0   255 0   0   1   0   -1.5062454  0.024833083 7.337884    -1.5073864  0.029565454
-1.5041572  18.78   0.005060006 8   8   0   0   -0.023542   -0.027803   5.926271    0   0   255 0   -1.5276097  0.030635118 91.725334   -1.527528   0.038933158
-1.5143325  -1.08   8   8   5.33E-04    0   0   0   0   -0.027872   0.04729855  85.258766   -1.529908   0   255 -1.5293596  0.009041548 -1.5280322  0.033451796
-1.4993688  14.52   8   8   0   -0.023884   -0.026326   0   0   255 0   0   0   0   -1.5211747  0.03198123  93.13916    -1.526189   0.013652086
-0.9816227  18.48   -1.32   8   8   0   0   0   -0.020971   -0.0265 -1.526189   0.5559387   7.78904 255 -1.0139774  0.030559063 85.279945   -1.0111967  0.031968236
-0.9756372  18.6    -1.2    8   8   0   0   -0.006156   -0.011322   0   0   255 0   1   -0.9895226  -0.0034725666   11.263685   -0.9939272  0.0069175363
-0.9923966  18.54   8   8   -0.0037284256   0   -0.010102   -0.010804   0   0   0   0   255 0   -1.011731   0.015144587 95.325294   -1.0129408  0.02712822
-0.7445967  0.12    8   8   0   -0.007972   -0.010841   0   0   255 0   0   0   0   -0.76289475 0.030269027 99.85943    -0.7639039  0.028285444
-0.18794483 19.62   -0.18   8   0   0   0.029863    0.031101    0   0   255 0   0   0   -0.19251534 0.0069647133    22.254642   -0.19720303 0.021827757

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对于我的三星Galaxy S5 G900I，当设备的方向已知时，屏幕方向传感器会在[0,3]范围内返回设备的方向。方向不确定时返回255

例如，如果设备正面或背面平坦，传感器报告255。类似地，如果设备处于纵向和横向两个方向之间的中间位置，则传感器报告255

这一切都是基于我自己的观察，而不是文件，因为屏幕方向传感器似乎不是标准的。我不记得在Android开发者文档中看到过任何关于该传感器的引用，SDK似乎也没有提及它