The CTandroidACL Android smartphone app streams accelerometer data (3 axes, up to 100Hz) to CloudTurbine files via FTP. Settings are configured in the Android user interface, shown on the right. Supply the host name where the FTP server is running, the FTP server username and password and the folder where data should reside. The default FTP port (21) is used. Data is flushed at the selected periodic interval (0.5, 1, 2 or 5 seconds).
Data is written to disk as a series of ZIP files. From the timestamps on the ZIP files in the figure below, you can see that in this case we had selected the “0.5s” flush period (i.e., a new ZIP file is written to disk nominally every 0.5 seconds). Each ZIP contains 3 data files, one for each channel: ax.f32, ay.f32 and az.f32. The figure below provides a peek into one of the ZIP files.
Each of the 3 sensor data files contains “packed” data – a concatenation of binary, single-precision floating point values. The number of samples in each data file depends on the flush interval that was specified in the user interface. For a 0.5 second flush interval and accelerometer data collected at 100Hz, each “.f32” file will contain 50 samples/200 bytes. The figure below shows an “octal dump” of one of the sensor data files; a single sensor reading is shown in the right-hand column of each row of output.
A more convenient way to view this data is with WebScan. The figure below shows an example displaying 10 seconds worth of data for all 3 channels.