[Shimmer-users] Different sampling rates for the accelerometer and the gyroscope

[Tifenn Rault]

Hello,

I am using Shimmer2 and I would like to sample the accelerometer at a
different rate than the gyroscope (e.g.: Accelerometer at 100 Hz and
Gyroscope at 50Hz).

In order to do this, is it correct to reset the shimmerAnalogSetup
before every sample, then add the corresponding channels (using either
addAccelInputs or addGyroInputs) and finally trigger the conversion and
get the values in DMA0.transferDone.

The objective to sample at different rates is to save energy through
adaptive sampling and to be able to enable/disable the gyroscope
dynamically independently of the accelerometer. Is it still efficient to
reset the shimmerAnalogSetup configuration before every sample?

Thank you for your help.

Tifenn

[mike healy]

Hi Tifenn,

The easiest thing to do would be to just power off the gyro every second
sample, but still sample those ADC lines (while discounting the results).
Actually sampling the 3 extra ADC channels will be insignificant in terms
of power compared with what the gyro itself is drawing.

But you should probably keep in mind that according to the datasheet for
the gyro chip the power on-time is up to 200ms (typical 50ms), so powering
it off for the 20ms between samples (sampling at 50Hs) is not going to be
advisable.

Mike

Hello,****
I am using Shimmer2 and I would like to sample the accelerometer at a
different rate than the gyroscope (e.g.: Accelerometer at 100 Hz and
Gyroscope at 50Hz).****
In order to do this, is it correct to reset the shimmerAnalogSetup before
every sample, then add the corresponding channels (using either
addAccelInputs or addGyroInputs) and finally trigger the conversion and get
the values in DMA0.transferDone.****
The objective to sample at different rates is to save energy through
adaptive sampling and to be able to enable/disable the gyroscope
dynamically independently of the accelerometer. Is it still efficient to
reset the shimmerAnalogSetup configuration before every sample? ****
Thank you for your help.****
Tifenn
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