Non power-of-two sampling freq. and sample count (OpenBCI)

Obtaining data from various hardware devices
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a1eks
Posts: 6
Joined: Sun Jan 21, 2018 6:26 pm

Non power-of-two sampling freq. and sample count (OpenBCI)

Post by a1eks »

Hi all,

Recently I have received OpenBCI Cyton+Daisy set (16ch version) and I have noticed that the device does not have power-of-two sampling rate. In particular, OpenBCI by Bluetooth connection I can set sampling rate to 250hz if I have 8ch or 125hz if I use all 16.

In the example of 16ch I cannot set the "sample per count" variable so that sampling_rate/sample_per_count is an integer. If I want to use 8 samples per count, I get 125/8= 15.625

Does that influence performance anyhow?

jtlindgren
Posts: 778
Joined: Tue Dec 04, 2012 3:53 pm
Location: INRIA Rennes, FRANCE

Re: Non power-of-two sampling freq. and sample count (OpenBC

Post by jtlindgren »

Hi, what do you mean by sample per count? The buffer (chunk) size in openvibe? I'm not sure if anything bad happens if the chunk size doesn't divide the sampling rate neatly. Its just the blocksize that acquisition server uses to pass out the samples.

Very small chunks cause more processing overhead to the cpu.

If you find some concrete and specific issues, let us know!


Cheers,
Jussi

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