The difference between two timestamps of the logged data is not constant
We tried using the Metawear App to log the accelerometer data at 400hz. We logged it for a few seconds and exported the data as CSV. In theory, the difference between two adjacent timestamps should be 2.5ms (1000ms / 400 = 2.5ms), right? But we looked at it closely, the difference is not constant, sometime 1ms, sometime 2ms and 3ms. We understand that the resolution of the timestamp is 1ms, so it makes sense for them(the timestamp difference) to be 2ms or 3m, due to rounding. But they shouldn't be 1ms.
We are just checking, when we log the accelerometer data at 400hz, is the sampling/collecting interval precisely and constantly at 2.5ms (we assume it has some internal precise 400hz trigger to trigger the SPI comm with the accelerometer)? If you can confirm that, we can ignore the time stamp.