EmBCI Shield

Overview

EmBCI Hardware is a wearable physiological signal amplifier system which can measure up to 8 channels of bio-potential data, including ECG, EEG, EMG and EOG.

Shield Features

  • 8 channels of 24-bit high pricise ADC

  • Configurable pre-processing (e.g. Notch/Bandpass filter, baseline etc.)

  • WiFi data UDP/TCP broadcasting

  • BLE/UART control interface

  • 3Axis accelerometer for physical information

  • Infrared/GPIO trigger system

Platform Features

  • SPI FIFO buffer

  • Rich calculation resources provided by Quad-A53 64bit ARM

  • Misc digital signal processing algorithms

  • WiFi data Lab-Streaming-Layer broadcasting

  • Web-based user interface

  • Websocket EventIO with <1ms latency

Specifications

TODO: list Shield attributes by key:value

Sampling

Analog Input

Accelerometer

Battery

Dimensions

Amplifier Pinout

Analog input OPi0+ Pin-out OPi0+2 Pin-out

Board Connection

  • Communicate with ADS1299 through SPI interface on OrangePi pin CS/PA13, CLK/PA14, MOSI/PA15 and MISO/PA16

  • On shield Atmega328P(Arduino Uno/Nano) connects to OrangePi by UART2_TX/PA00 and UART2_RX/PA01. Deprecated

  • On shield ESP32 is used as Data Buffer to cache raw data from ADS1299 and send out preprocessed data chunk by chunk as SPI slave. Benefit from ESP32’s precise clock cycle and rich calculation resource, many important IO features are implemented.

  • Control SSD1306 0.96’ OLED screen by SPI or ILI9325 2.3’ LCD screen through on shield Arduino by serial. Deprecated

  • EmBCI broadcasts collected biosignal data by two ways: Lab-streaming-layer and TCP Server. Before you fetch data through network, make sure that your device and EmBCI machine are in a same local network. You can create a hotspot for EmBCI or login your device to the hotspots created by it.

Electrodes

Passive electrodes have no inbuit circuitry. You may need paste/gel between it and subject’s skin/scalp for better signal. Electrodes can be round or needle metal things coated with special alloys, for example gold, tin and silver. Ag / AgCl are supposed to be best.

Comparing to passive electrodes, active electrodes work by putting a unity-gain amplifier right next to the electrode up on the scalp. This greatly improves the signal quality and avoids the skin preparation like conductive paste and gel.

A brief history of active eletrodes:

  • Jarek Foltynski created the initial designs and prototypes. Bioera-AE

  • Joerg Hansmann refined the v2 circuit design.

  • Ian Vincent introduced the idea of using multiple-pin electrodes which can pass through the hair easily.

  • Joe Street created a modified design using power cells instead of requiring power from ADC board. Joe-AE

  • Jim Peters constructed a version of Joerg’s design. EEG-AE

  • Pedro Ortega created a simplified version without the shielding/guarding. Peortega-AE