Add GND as reference option for Neuropixels 2.0

[bparks13]

Currently the only reference options available for Neuropixels 2.0 probes are EXT, and TIP1-4. On commercial probes, GND is a valid option for references.

This would only be an option for non-beta probes. We need to go ensure that the correct bits are being turned on/off in the shank config for GND to properly be activated.

This will only be reflected at the GUI level by an additional entry in the drop-down menu, and all configuration will still be handled by the configuration methods in the base library.

[jonnew]

@jsiegle In order to do this with 100% certainty, we either need the API source code that IMEC is using or we need a i2c trace of probe configuration when GND is selected as the reference. Can you help to provide either of these?

[bparks13]

@jonnew

Adding GND as a Reference Option

Based on the documentation given by IMEC, it looks like the configuration for using GND as reference can be done by setting the referenceBit to 3.

For this library, that can be accomplished by adding an entry to the NeuropixelsV2QuadShankReference
to use GND as a reference, and then adding a line to the referenceBit switch to set it to 3.

Question: What should the displayed name for GND be? Based on the other two names, and how it is represented in the documentation, we have the following options: GND, Gnd, or Ground. Given that we fully write out External as an option, I am leaning towards Ground.

Differentiate Between Beta and Non-Beta Probes

The changes above will automatically propagate to the GUI, as it pulls the possible values of NeuropixelsV2QuadShankReference for the combo box, so these two changes are sufficient to give users full ability to select GND. However, this presents a complication; the GND option is only available for non-beta probes, and currently there is no distinction between the probe configuration for beta vs. non-beta probes. Specifically, both probes use the same dialog (NeuropixelsV2eProbeConfigurationDialog) and the same class (NeuropixelsV2QuadShankProbeConfiguration). So, now we need some way to differentiate between beta and non-beta probes, both at the level of the Bonsai editor and the GUI.

Since there is a lot of overlap between the probe configurations, I don't think it makes sense to create a new class to differentiate between beta and non-beta probes, since as of right now the only difference is whether or not GND can be used as a reference.

Bonsai Editor

Currently in main, there is no way to expand the ProbeConfiguration to see/modify the reference, but there is a PR with a commit that allows expanding of properties such as the ProbeConfiguration, so we should be aware of this and assume that in the near future the editor will need a way of filtering.

Dialogs

The dialogs expose the reference options in a ComboBox by calling Enum.GetValues(typeof(NeuropixelsV2QuadShankReference));. We can modify this in some way so that if it is a beta probe, then instead it becomes:

comboBoxReference.DataSource = Enum.GetValues(typeof(NeuropixelsV2QuadShankReference))
                                   .Cast<NeuropixelsV2QuadShankReference>()
                                   .Where(x => x != NeuropixelsV2QuadShankReference.Ground)
                                   .ToList();

Overlap with Other Issues

Since the scope of the issue is increasing to need some way of differentiating between beta and non-beta, there is overlap with #446, which will require re-working the V2 probe configuration to work with single- and quad-shank probes. I believe it makes sense to work on both of these issues concurrently, by implementing any major changes in the other branch and then using that as a starting point for this issue.

I will expand on my proposal for that issue on the issue itself, but in a nutshell I believe that it will make the most sense to rename NeuropixelsV2QuadShankProbeConfiguration => NeuropixelsV2ProbeConfiguration, and add two new readonly properties; NumberOfShanks and IsBeta. The number of shanks is relevant for #446, but knowing if the probe is a beta probe is relevant for this issue, and could be what is used to decide whether or not to filter the enum list, as shown above.

[bparks13]

Rather than adding fields to the probe configuration and determining if it is a beta probe or not, allow the user to set the bit. Add warnings to the documentation not to do this, but otherwise leave it alone.

Spell out Ground for the enum value.