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cortex-lab / neuropixels

Information about Neuropixels electrode arrays
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Basestation grounding #12

Open brykko opened 7 years ago

brykko commented 7 years ago

Hi all,

I want to test using TTL between the neuropixels basestation and another piece of hardware, and presumably it's necessary for both systems to share a common ground. I would prefer to do this test without connecting the probe flex ground, so I wondered, does the basestation have a ground connection I could use instead? The manual seems to state that it does (on p.25):

Grounding of the basestation connect board to earth ground, prior to connecting the probe flex to the headstage (as indicated in Figure 34 and Figure 36)

Has anyone else done anything like this? Any advice is appreciated! Rich

apfdomanski commented 7 years ago

Hi Rich, To share a digital sync pulse you could ground your TTL line against any of the breakout pins marked Vss in Fig 13/table 1, (i.e. pins 5,10,15,20,23,24). hope that helps. Cheers, Aleks

apfdomanski commented 7 years ago

Also speaking of shared systems, I should add, I've had some success integrating chronic Neuropixel probe recordings with LFP wire and skull screw recordings (Open Ephys), synchronising via a shared TTL strobe pattern between the two systems. If anyone goes this route, tread carefully and make sure there's no offset potential between the grounds of the two systems. I use the shell of the SMA connector next to the headstage Omnetics connector on the Neuropixel basestation's FMC breakout for this purpose. There's some residual noise, putatively from a residual ground loop and/or altered CMR based on different electrode impedances. Powering the FPGA dev board and the OE system from the same DC source helps further reduce this, as well as standard good noise hygiene regarding ground loops, shielding and the orientation of crossing supply cables.

brykko commented 7 years ago

Thanks a lot, Aleks – I had wondered what those Vss pins were for! Should the Vss pins and the shell of the "to headstage" SMA connector work the same for grounding purposes?

Actually I'm also trying to set up simultaneous recording from Neuropixels and an Intan RHD2000 board. I'm totally new to Open Ephys, but it at first glance it seems to run smoothly when acquiring from both systems. However, one thing that I miss from SpikeGLX is the handy tool for viewing spike rates across the whole probe – do you know if there's anything like this available in Open Ephys?

nsteinme commented 7 years ago

I'm not aware of such a visualization in open-ephys. If Aleks knows this then great - otherwise you might try the open-ephys github page: https://github.com/open-ephys/GUI/