[Shimmer-users] Different Sampling Rates in Matlab API

[Nick Bianco]

Hi,

I've been working with Shimmer3 units for a few weeks now and I'm trying to
nail down the extent of their capabilities. My goal is to simultaneously
collect inertial data around 64 Hz and EMG data around 1000 Hz with
multiple units. I was unsatisfied with the Multi Shimmer Sync software
since it restricts all sensors to a common sampling rate. I have since
moved on to the Matlab API which has more flexibility in setting individual
sampling rates for individual sensors. However, I am not sure that I'm
getting the results that I'm looking for.

After manually setting the inertial sensors to the value closest to 64 Hz
and the EMG channels to 1000 Hz, I use the GETDATA command to retrieve the
data from the buffer. If I capture data for 5 seconds I would expect to
data in columns of varying length based on each samping rate, however this
is not the case. Instead, I receive a matrix with columns of equal length
resampled to a time stamp that is not consistent with any of the sampling
rates I set (512 Hz).

What is going on here? Does the real data get collected at these rates and
then repackaged within the CAPTUREDATA function as it is retreived from the
buffer? Or something else? I am having difficulty seeing where this happens
within the ShimmerHandleClass. Forgive me if I'm unclear, I'm relatively
new to this technology.

Any help on this would be appreciated!

Regards,
Nick