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32-channel EEG ADC with Cortex-M7 ----FreeEEG32

by: Sep 30,2020 3937 Views 0 Comments Posted in Activities

32-channel EEG ADC Cortex-M7 FreeEEG32 open source STM32H7 microcontroller

What is FreeEEG32?

FreeEEG32 is a stackable, open source 32-channel (4 ADCs x 8 channels ea.), 24-bit, sigma-delta, simultaneous sampling board meant to satisfy scientists and hackers who want research-grade equipment without breaking the bank. NeuroIDSS has been developing this EEG for several years now as the definitive open source answer to expensive, proprietary EEG technology.

The FreeEEG32 mixes four AD7771 ADCs with ultra-low noise sources and references (<0.22 μV measured) and a powerful STM32H7 ARM Cortex-M7-based chipset to drive them and perform pre-processing. This is sensitive enough for high-quality EEG data acquisition and much, much more.

Board stacking for 64-256 channels or more makes FreeEEG32 the most affordable high density EEG system on the market. Stacking is done vertically in order to maximize stability and accessibility.

FreeEEG32 is part of an ongoing scientific project to probe working memory in the brain and measure theta and gamma correlations with memory encoding. It is available under the Affero-General Public License (AGPL).

Project files are available at: https://github.com/neuroidss/FreeEEG32-beta

Features & Specifications:

Four AD7771 Analog-to-Digital Converters

  • 24-bit, up to 128 kSPS simultaneous sampling*
  • Eight channels per ADC
  • Up to 8x programmable gain
  • 107 dB dynamic range at 32 kSPS
  • Onboard SAR (Successive-Approximation-Register) ADC for diagnostics

STM32H7 ARM Cortex M-7 Microcontroller

  • 480 MHz CPU
  • 1027 DMIPS (Dhrystone Million Insturctions Per Second)
  • 2 MB flash, 1 MB SRAM, 16 kB L1-cache
  • Double-precision floating point unit (FPU) for deep learning, etc.
  • Chrom-ART graphics acceleration
  • Dozens of communication protocols

Separate USB ports for power and data

  • With isolated power and logic

SD card slot for data collection or extended program storage

We're also testing an accelerometer for basic movement tracking when the device is head-mounted

* To meet EEG standards, FreeEEG32’s firmware is optimized for 512 SPS per channel when running all 32 channels simultaneously

FreeEEG32 is currently in development. It will coming soon on CrowdSupply, go to support it!

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