TTL Event timestamps.npy sporadically not recording properly.

[Adam Harris]

Hi,

I'm having an issue where my timestamps.npy file - that contains info about TTL pulse events - sporadically doesn't save actual TTL pulse times. Instead, it contains only negative numbers with no apparent structure (as in, not just -ve versions of what the pulse times should be). 

This happens around 50% of the time, and I have not been able to figure out any reason why it happens in some cases and not others. 

I am able to see the TTL pulses in the OpenEphys display, and the pulses are being picked up correctly by my camera acquisition setup.

I am acquiring Neuropixels data, and my TTL pulses are being generated by a PyControl board hooked up to the Neuropixels acquisition box directly by a BNC cable.

Does anyone know what might be going on here?

Thanks!

Adam

[Josh Siegle]

Hi Adam,

This can happen when the online synchronizer in the Record Node gets into a weird state. We're not exactly sure what causes this, but it can usually be avoided by stopping and re-starting acquisition, waiting for the sync icons to turn green, then starting recording. We're working on building a richer interface for querying the state of the synchronizer, so situations like these will be more obvious while recording, but it's not ready for release yet.

For the data you've already collected, you can generate the timestamps offline using the TTL sample numbers. An example of how to do that using the `open-ephys-python-tools` library is available here: https://github.com/open-ephys/open-ephys-python-tools/tree/main/src/open_ephys/analysis#synchronizing-timestamps

Josh

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