Uneven sampling and false zero-motion values of the accelerometer readings (better read to understand)
Firstly, I don't know why I wanted to start working with smartphone sensors. The real fact is that in principle I thought that woking with IMUs and smartphones would have been roughly the same thing, well it seems not.
The problem I am facing is related to the movement I am trying to observe/measure. Imagine you hold your smartphone in one hand horizontally and meanwhile you are walking with the Y-axis of the body (smartphone) reference system pointing in the same direction of motion, you swing that smartphone producing like a number of 8 movements around the Y-axis (so around the pitch), for about 10 seconds in total.
PROBLEM: The data log shows strange jumps not only in the time stamp (as expected due to the smartphone platform/OS), but also in the readings of the accelerometer which as it is clearly shown in the image here attached, produces new steady values between different swings. I cannot explain myself how the accelerometer could measure different values than the expected due to the uneven sampling of the smartphone sensors (since it seems to occur whenever there is a jump on the time stamp). The same holds for the magnetometer.