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FIG. 27: The Configure tab contains miscellaneous
controls and text fields that are appended to
saved data files.
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SOFTWARE
Configure Tab
The software also contains a feature that allows the user to lock DAC 1 to the currently selected electrode channel. This may be useful when examining
many amplifier channels while using an audio monitor.
Additionally, users have the ability to set thresholds for the each of the signals routed to a DAC. The FPGA on the USB interface board implements
low-latency comparators that generate digital signals on Digital Output Lines 0-7 indicating when a particular signal exceeds the selected threshold
level. This feature can be used to trigger external events based on the detection of neural spikes, for example. The typical latency from electrode to
comparator digital output is less than 200 μs. If low-frequency signals (e.g., local field potentials) are present in the waveforms, the software/DAC filter
can be used to isolate the spikes while preserving the wideband waveforms in the saved data (see the “Bandwidth” tab for software/DAC filter set-
tings). Using this filter in concert with the audio noise slicer function will maximize the audibility of neural spikes.
Clicking on the small buttons labeled with question marks brings up help windows that explain the operation of these features in more detail.
The “Configure” tab contains a variety of miscellaneous tools for working with amplifier boards connected
to the USB interface board (see FIG. 27). The “Rescan Ports A-D” button causes the USB interface board to
search for connected amplifier boards on all SPI ports, and to account for any signals delays due to long in-
terface cables on these ports. This function is automatically executed when the GUI starts, but if any boards
are unplugged or reconnected, or cable lengths are changed, then this button should be clicked to update
the status of all ports. If noisy, discontinuous data is observed on one of the SPI ports, this may be due to an
inaccurate compensation of signal delay. The automatic signal delay estimation algorithm may be overridden
by clicking the “Manual” button to bring up a dialog box allowing the delay compensation for selected SPI
cables to be set manually. RHD2164 64-channel amplifier chips use a double-data-rate SPI protocol and are
particularly sensitive to this delay setting, so it is sometimes necessary to adjust the delay manually when
using these chips.
The “Auxiliary Digital Output Pins” box contains a button that brings up a dialog box allowing the user to
configure real-time control of the auxiliary digital output pin (
auxout
) on each SmartProbe
™
connected to
the SmartBox
™
. This pin is brought out to a solder point labeled DO on some amplifier boards, and can drive
p.18