1 This directory contains a simple python script for visualizing 2 the behavior of the WindowOrientationListener. 3 4 5 PREREQUISITES 6 ------------- 7 8 1. Python 2.6 9 2. numpy 10 3. matplotlib 11 12 eg. sudo apt-get install python-numpy python-matplotlib 13 14 15 USAGE 16 ----- 17 18 The tool works by scaping the debug log output from WindowOrientationListener 19 for interesting data and then plotting it. 20 21 1. Plug in the device. Ensure that it is the only device plugged in 22 since this script is of very little brain and will get confused otherwise. 23 24 2. Enable the Window Orientation Listener debugging data log. 25 adb shell setprop debug.orientation.log true 26 adb shell stop 27 adb shell start 28 29 3. Run "orientationplot.py". 30 31 32 WHAT IT ALL MEANS 33 ----------------- 34 35 The tool displays several time series graphs that plot the output of the 36 WindowOrientationListener. Here you can see the raw accelerometer data, 37 filtered accelerometer data, measured tilt and orientation angle, confidence 38 intervals for the proposed orientation and accelerometer latency. 39 40 Things to look for: 41 42 1. Ensure the filtering is not too aggressive. If the filter cut-off frequency is 43 less than about 1Hz, then the filtered accelorometer data becomes too smooth 44 and the latency for orientation detection goes up. One way to observe this 45 is by holding the device vertically in one orientation then sharply turning 46 it 90 degrees to a different orientation. Compared the rapid changes in the 47 raw accelerometer data with the smoothed out filtered data. If the filtering 48 is too aggressive, the filter response may lag by hundreds of milliseconds. 49 50 2. Ensure that there is an appropriate gap between adjacent orientation angles 51 for hysteresis. Try holding the device in one orientation and slowly turning 52 it 90 degrees. Note that the confidence intervals will all drop to 0 at some 53 point in between the two orientations; that is the gap. The gap should be 54 observed between all adjacent pairs of orientations when turning the device 55 in either direction. 56 57 Next try holding the device in one orientation and rapidly turning it end 58 over end to a midpoint about 45 degrees between two opposing orientations. 59 There should be no gap observed initially. The algorithm should pick one 60 of the orientations and settle into it (since it is obviously quite 61 different from the original orientation of the device). However, once it 62 settles, the confidence values should start trending to 0 again because 63 the measured orientation angle is now within the gap between the new 64 orientation and the adjacent orientation. 65 66 In other words, the hysteresis gap applies only when the measured orientation 67 angle (say, 45 degrees) is between the current orientation's ideal angle 68 (say, 0 degrees) and an adjacent orientation's ideal angle (say, 90 degrees). 69 70 3. Accelerometer jitter. The accelerometer latency graph displays the interval 71 between sensor events as reported by the SensorEvent.timestamp field. It 72 should be a fairly constant 60ms. If the latency jumps around wildly or 73 greatly exceeds 60ms then there is a problem with the accelerometer or the 74 sensor manager. 75 76 4. The orientation angle is not measured when the tilt is too close to 90 or -90 77 degrees (refer to MAX_TILT constant). Consequently, you should expect there 78 to be no data. Likewise, all dependent calculations are suppressed in this case 79 so there will be no orientation proposal either. 80 81 5. Each orientation has its own bound on allowable tilt angles. It's a good idea to 82 verify that these limits are being enforced by gradually varying the tilt of 83 the device until it is inside/outside the limit for each orientation. 84 85 6. Orientation changes should be significantly harder when the device is held 86 overhead. People reading on tablets in bed often have their head turned 87 a little to the side, or they hold the device loosely so its orientation 88 can be a bit unusual. The tilt is a good indicator of whether the device is 89 overhead. 90
