Affordable, stackable, and open source 32-channel EEG ADC with Cortex-M7

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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.

Open Source Science

FreeEEG32 is part of an ongoing scientific project to probe working memory in the brain and measure theta and gamma correlations with memory encoding. This project is dedicated to science and discovery and all those who undertake it. It is entirely open access and in the spirit of improving global scientific discourse and community. We endeavor to get these increasingly important tools to the masses so we all may participate in one of the most important scientific projects of our era: solving the brain.

FreeEEG32 is available under the Affero-General Public License (AGPL). Project files are available at:

General Purpose Signal Acquisition

This board is specialized for EEG, meaning all considerations have been made for noise control and power isolation for safety. However, the board works as a general purpose signal acquisition device, meaning you can have 32-channel, 24-bit simultaneous sampling for all your signal analysis needs. For example:

  • Non-EEG bio-signal acquisition and imaging
  • Creating other types of high-channel signal analysis devices
  • Environmental sensing like for industrial process control
  • ELF and ULF radio signal acquitision
  • Smart home management
  • Power/noise measurement

OpenVibe hooked up to output audio for multi channel theta & gamma data, a concert of your mind! PureData support is made possible by a community member.

Up to 256 Channels

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.

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

See Also

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