Page 1 of 1

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

Posted: Thu May 03, 2018 2:16 pm
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?

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

Posted: Fri May 04, 2018 2:14 pm
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