question regarding Ganglion sample index and timestamps

wmmzbwmmzb beijing
edited May 2025 in Ganglion

I have the following several questions。
1、Why is the Sample Index repetitive, such as 2 2?
2、Why is the time on the right also repetitive?
3、The top left corner shows "Sample Rate = 200 Hz". Why is the sampling frequency obtained by subtracting the time from the right corner different

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Hi Wmm,

    Each Ganglion radio packet contains TWO sample values. This is why the Sample Index repeats once for each sample pair.

    Timestamps are assigned NOT at the Ganglion board, but when the radio packets travel through the USB or Bluetooth OS interface and arrive at the Brainflow library / GUI. So expect some buffering delays. Timestamps cannot be used for precise timing. Sample rate of Ganglion is 200.xx Hz, which stays constant, but the offset from 200.000 stays constant. For example the actual sample rate may be 200.02 Hz, or 199.98, etc.

    William

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