STEVAL WESU1 understanding logged data

[abhi1new]

Posted on October 26, 2016 at 16:43

Hi , 

I have STEVAL WESU module  and logged acelerometer data using android app. (plz see attached file)

My settings are: 

Timer: 512 Hz, 10Hz, 1Hz

MEMS Accelerometer output data rate: 416 Hz , 833 Hz, 100Hz

In the logged data host time stamps and node time stamps are available. 

My  observation:

All the time stamps are in milliseconds.

Host, stamp time on data at 100Hz if Timer value > 100Hz otherwise at Timer value. 

Node, stamp time on data at 1000Hz irrespective of ''MEMS Accelerometer output data rate'' settings. 

If Host time stamp rate  lower than node time stamp,  then are we losing data? What is allowable max. data rate at which we can log accelerometer data considering BLE protocol? As per sensor data sheet 1Hz- few kHz data rate is allowed. 

thank you, 

#steval-wesu

[abhi1new]

Posted on November 03, 2016 at 13:38

******Bump

Any one from moderators plz comment^^^^

[Adriano BASILE]

Posted on February 01, 2017 at 11:44

Hi

 NodeTimeStamp is a Counter to permit host to re-order data frames, in fact the BLE HW (from both sides: Smartphone and WeSU) could not respect the correct time sequence. Since the frequency set in 'Node Configuration Setting' in the App is the one you have to consider.

What is the maximum frequency?

Answer: it depends by how many data you are transmitting, you can act on Settings -> Node Configuration Setting -> Data Read GROUP A & Data Read GROUP B activating only the data you need and configure the Timer increasing the frequency.

Furthermore you have to modify Advanced MEMS Settings -> Output Data Rate of sensor you would retrieve accordantly with Timer Frequency.

Please Note: Output Data Rate accept any digit rounding it to the next available setting.

Final Note: also the phone model could affect the maximum data rate.