Knight Board Specs

Knight Board

The Knight Board is NeuroPawn’s core biopotential acquisition PCB. It is designed for 8-channel EEG, EMG, ECG, EOG, and general ExG acquisition over a USB-C connection.

EEG Sensors

Parameter	Value
Channels	8, adjustable gain (1 – 12)
Reference	Auricular (ear clip)
Electrode types	Dry spike, wet spike, gold-cup, EMG, ECG, active

EEG Signals

Parameter	Value
Sampling method	Referential or bipolar montage, 8 × 16-bit ADC
Supported sample rates	125 / 250 / 500 SPS
Default sample rate	125 SPS
Detection range	±333 mV
Detection step	10.2 µV (at gain = 12)
Bandwidth	1 – 62.5 Hz
Filtering	Common-mode noise filter, 50/60 Hz notch (2nd order)
CMRR	−120 dB
Software	BrainFlow, LSL, NeuroPawn EXG Visualizer

Connectivity & Power

Parameter	Value
Connection	USB-C (bus-powered)
Operating voltage	5 V
Streaming	Real-time

Channel Switches

Each of the 8 input channels has a dedicated slide switch on the board.

• Switch toward the header — channel OFF (common reference input disconnected)
• Switch away from the header — channel ON (common reference input active)

Channels are labelled 1 – 8 on the silkscreen. Unused channels should be switched off to minimise crosstalk and noise on adjacent active channels. For simplicity, we say that switches “turn off” channels, in reality this is not what is happening. Switching toward the headers routes the channel’s negative input directly to the header instead of the common reference pin. In some instances, users may want to have individually addressable references for experiments that involve capturing 2 different types of biosignals (example: EEG, and EoG).

Electrode Connector Pinout

Each channel exposes a negative (N) and a positive (P) input. Channels are labelled on the board in the form N X P, where:

• N is the negative input on the left rail,
• X is the channel number (1 – 8),
• P is the positive input on the right rail.

For example, channel 3’s inputs are labelled N3 (left) and 3P (right).

Pin label	Description
N1 – N8	Negative input for channels 1–8 (left rail)
1P – 8P	Positive input for channels 1–8 (right rail)
COMM	Common reference input (connect to reference electrode, e.g. ear clip)
RLD	Right-leg drive output (connect to driven reference electrode for noise reduction)

Tip

For most EEG setups, connect the ear clip to COMM and optionally to RLD. Enabling RLD in software reduces power-line interference significantly.

Gain Settings

The Knight Board supports per-channel programmable gain. The default gain is 12. Available values are 1, 2, 3, 4, 6, 8, 12.

The voltage scale factor — the number of microvolts represented by each raw count — is derived from the ADC’s full-scale reference, its 16-bit signed resolution, and the selected gain:

$$\text{Scale Factor}\;(\mu V/\text{count}) = \frac{4}{2^{15}-1} \times \frac{1}{\text{gain}} \times 10^6$$

At the default gain of 12, this works out to an ADC step voltage of ≈ 10.2 µV/count.

Gain	Scale factor
1	122.4 µV/count
2	61.2 µV/count
3	40.8 µV/count
4	30.6 µV/count
6	20.4 µV/count
8	15.3 µV/count
12 (default)	10.2 µV/count

In firmware/driver code the same calculation appears as:

Knight Board EEG scale factor

float eeg_scale = 4 / float ((pow (2, 15) - 1)) / 12 * 1000000.;

To select a gain in BrainFlow, pass it through other_info:

Setting gain via BrainFlow

params.other_info = '{"gain": 6}'  # any value from: 1, 2, 3, 4, 6, 8, 12