Cerelog BCI/EEG Board User Guide

1. Critical Safety & Legal Notices

2. Prerequisites: What You'll Need

Hardware & Accessories (Not Included)

The following links point to recommended third-party vendors. Cerelog Inc. is not affiliated with these vendors and assumes no liability for their products.

• Power Source: A 3.7V LIPO battery is recommended for portable, untethered use. (Qty: 1, Recommended)
• Data Cable: A high-quality USB-C cable rated for data transfer. (Qty: 1)
• EEG Electrode Cap: A professional cap for placing electrodes on the scalp. (Qty: 1)
• Electrode Gel/Paste: Conductive gel for a low-impedance connection. (Qty: 1)
• Touch-Proof Adapters: Essential for connecting the electrode cap to the board. (Qty: 2, for default setup)

  IMPORTANT: Adapter Requirements

  • The board's default firmware (Sequential Montage) requires TWO (2) Adapters to use all 8 channels.
  • To use the board with only ONE (1) adapter, you must switch to Referential Montage by modifying the firmware (See Section 6).

Software & Development Tools

• A code editor, like VS Code.
• Python (version 3.7 or newer).
• Git for cloning software repositories.
• For Advanced BrainFlow use (Method B):
• Microsoft C++ Build Tools (on Windows) or equivalent build essentials on Mac/Linux.
• CMake.

3. Hardware Overview

• USB-C Port: For data streaming, powering the board, and charging a connected LIPO battery.
• JST-PH Battery Connector: 2.0mm pitch connector for an optional 3.7V LIPO battery.
• Electrode Header Pins: Two 10-pin headers for connecting the touch-proof adapters. The SRB1 pin on the ADC is used for referential montage mode (requires firmware change).
• Power LED (Green): Located below the Status LED, this indicates the board is receiving power from USB or a battery.
• GPIO17 Status LED (Green): This LED indicates the firmware status:
  • SOLID ON: Firmware has finished loading, and the board is ready to connect and stream data.
  • OFF: Board is not powered, or firmware has not loaded.
• Battery Charge Status LED: Located to the left of the power switch (not labeled on the diagram). This LED indicates the charging status of a connected LIPO battery: RED when charging, and GREEN when fully charged.
• Onboard Motor: A tactile feedback motor that can be controlled via custom firmware. Note that activating it will introduce noise into EEG signals.

4. Software Setup & First Data Stream

This section guides you through installing software to visualize your EEG data.

Step 1 (Optional): Install Drivers if Needed

Modern operating systems like Windows 10/11 and recent versions of macOS/Linux should recognize the board automatically. Only follow this step if your computer fails to detect the board or assign it a COM port.

Step 2: Choose and Configure Your Visualization Method

import time
import numpy as np
import matplotlib.pyplot as plt

from brainflow.board_shim import BoardShim, BrainFlowInputParams, BoardIds, BrainFlowError

def main():
    """
    A simple script to connect to a BCI, collect data for a few seconds,
    and then plot the EEG data.
    """
    # Board and acquisition parameters
    board_id = BoardIds.CERELOG_X8_BOARD
    duration_seconds = 10

    # --- 1. SETUP THE BOARD ---
    # BrainFlow uses a params object to configure the board
    params = BrainFlowInputParams()
    
    # Create the BoardShim object
    board = BoardShim(board_id, params)

    # Use a try/finally block to ensure session is always released
    try:
        # Get board info using static methods
        eeg_channels = BoardShim.get_eeg_channels(board_id)
        timestamp_channel = BoardShim.get_timestamp_channel(board_id)
        sampling_rate = BoardShim.get_sampling_rate(board_id)

        print(f"Connecting to {board.get_board_descr(board_id)['name']}...")
        print(f"EEG Channels: {eeg_channels}")
        print(f"Sampling Rate: {sampling_rate} Hz")

        # Prepare the session (finds the board and establishes connection)
        board.prepare_session()

        # --- 2. ACQUIRE DATA ---
        print(f"\nStarting stream for {duration_seconds} seconds...")
        board.start_stream()
        time.sleep(duration_seconds)
        
        # Stop the stream and get the data from the internal buffer
        board.stop_stream()
        print("Stream stopped. Getting data...")
        data = board.get_board_data()

        if data.size == 0:
            print("Error: No data was collected.")
            return

        # --- 3. PROCESS AND PLOT DATA ---
        # Get the specific data streams from the data array
        eeg_data = data[eeg_channels]
        timestamps = data[timestamp_channel]

        # Create a time axis starting from 0
        time_axis = timestamps - timestamps[0]

        print("Plotting data...")
        plt.figure(figsize=(15, 8))

        # Plot each EEG channel with a vertical offset for clarity
        offset_value = 150 # µV
        for i, channel_data in enumerate(eeg_data):
            plt.plot(time_axis, channel_data + i * offset_value, label=f'Channel {eeg_channels[i]}')

        # Add titles and labels for clarity
        plt.title(f'{duration_seconds} Seconds of Cerelog EEG Data')
        plt.xlabel('Time (s)')
        plt.ylabel('Voltage (µV) - Channels are offset for clarity')
        plt.legend(loc='upper right')
        plt.grid(True)
        plt.tight_layout()

        # Show the plot
        plt.show()

    except BrainFlowError as e:
        print(f"BrainFlow Error: {e}")
    except Exception as e:
        print(f"An unexpected error occurred: {e}")
    finally:
        # --- 4. CLEAN UP ---
        # Always release the session to free the COM port
        if board.is_prepared():
            print("\nReleasing session.")
            board.release_session()

if __name__ == "__main__":
    main()

5. Running an EEG Session

1. Hardware Assembly: Connect your EEG cap cable(s) to the required touch-proof adapter(s), then plug the adapter(s) into the electrode headers on the Cerelog board.
2. Prepare the Subject: Fit the EEG cap on the subject's head. Apply a small amount of conductive gel into each electrode cavity to ensure good skin contact.
3. Connect Bias Probe: Securely attach the bias drive (BIAS) electrode. A poor connection on this probe is a common cause of noisy data.
4. Connect and Stream: Connect the board to your computer via USB-C. Launch your chosen software or script, and start the data stream.

   ⚠️ Safety Reminder

   As per the notice in Section 1, only connect to a laptop running on its own battery power. **DO NOT** use this device if the laptop is charging or connected to a desktop computer plugged into a wall outlet.

5. Check Signal Quality: Observe the incoming data. If a channel is flat or excessively noisy, check the corresponding electrode's position and consider re-applying a small amount of gel.

6. Advanced Usage: Firmware Customization

Modifying the firmware is necessary to:

• Change Electrode Montage: Switch from the default Sequential mode to Referential mode. This enables the SRB1 pin on the ADC as a common reference, allowing you to use a single 10-pin adapter.
• Adjust Gain: Change the Programmable Gain Amplifier (PGA) setting (1, 2, 4, 6, 8, 12, or 24).
• Control Peripherals: Write custom code to activate the haptic feedback motor or use the debug LEDs.
• Change Sample Rate: This is a highly advanced modification. Altering the sample rate or resolution will change the data stream format and will require you to rewrite the data parsing logic in your software.

7. Troubleshooting Guide

Problem: Board not detected (no COM port appears).

- First, try a different USB port and ensure you are using a USB-C data cable, not a charge-only one.
- If it's still not detected, proceed with the optional CP210x driver installation in Section 4.
- Check for the green power LED on the board. If it's not on, there is a power issue.

Problem: My script fails to connect.

- Make sure the green status LED is on before running your script. This indicates the firmware is loaded and ready.
- Try a full power cycle. Disconnect the USB-C cable, wait a few seconds, and plug it back in before re-running your script.
- Make sure no other program is already connected to the board's COM port. Only one application can use the port at a time.
- If you recently flashed new firmware, see the "Procedure After Flashing" notes in Section 6.

Problem: Data is extremely noisy or flat.

- Poor electrode connections are the most common cause of bad signal quality. Ensure that all electrodes, especially the **BIAS probe**, have a secure, low-impedance connection.
- Ensure you are not near sources of high electromagnetic interference (e.g., power bricks, fluorescent lights, powerful fans).
- Re-apply conductive gel to the problematic electrodes.

8. Product Demonstrations

See the Cerelog ESP-EEG board in action. These demos showcase the real-time data streaming and BCI control capabilities.

9. Applications & Possibilities

This board is a versatile tool for developers and researchers. With custom software, you can explore a wide range of applications.

• Multimodal Signal Acquisition: Capture data for EEG (brain), EMG (muscle), ECG (heart), and EOG (eye movement).
• Neuroscience Paradigms: Design experiments based on P300, Event-Related Potentials (ERP), and Steady-State Visually Evoked Potentials (SSVEP).
• BCI & Control Systems: Develop systems to quantify cognitive or emotional states, or to control robotics and other external devices.

10. Appendix: Pinout & Technical Details

Electrode Header Pinout

Technical Specifications

Understanding Electrode Montages

The board can be configured in two primary ways:

• Sequential / Bipolar Montage (Default): Each channel measures the potential difference between a positive input (INxP) and a negative input (INxN). For example, Channel 1 is (IN1P - IN1N). This is the default firmware configuration and requires two 10-pin adapters to use all 8 channels.
• Referential Montage (Requires Firmware Mod): Each channel measures the potential difference between a positive input (INxP) and a common reference. To enable this, the firmware must be modified to internally connect all negative inputs (INxN) to the SRB1 pin. This configuration requires only a single 10-pin adapter.