[HN Gopher] Show HN: Open-Source 8-Ch BCI Board (ESP32 and ADS12...
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Show HN: Open-Source 8-Ch BCI Board (ESP32 and ADS1299 and OpenBCI
GUI)
Hi HN, I recently shared this on r/BCI and wanted to see what the
engineering community here thinks. A while back, I got frustrated
with the state of accessible BCI hardware. Research gear was wildly
unaffordable. So, I spent a ton of time designing a custom board,
software and firmware to bridge that gap. I call it the Cerelog
ESP-EEG. It is open-source (Firmware + Schematics), and I designed
it specifically to fix the signal integrity issues found in most
DIY hardware. I believe in sharing the work. You can find the
Schematics, Firmware, and Software setup on the GitHub repo: GITHUB
LINK: https://github.com/Cerelog-ESP-EEG/ESP-EEG For those who
don't want to deal with BGA soldering or sourcing components, I do
have assembled units available:
https://www.cerelog.com/eeg_researchers.html The major features:
Forked/modified OpenBCI GUI Compatibility as well as Brainflow API,
and LSL Compatibility. I know a lot of us rely on the OpenBCI GUI
for visualization because it just works. I didn't want to reinvent
the wheel, so I ensured this board supports it natively. It works
out of the box: I maintain a forked modified version of the GUI
that connects to the board via LSL (Lab Streaming Layer). Zero
coding required: You can visualize FFTs, Spectrograms, and EMG
widgets immediately without writing a single line of Python. The
"active bias" (why my signal is cleaner): The TI ADS1299 is the
gold standard for EEG, but many dev boards implement it
incorrectly. They often leave the Bias feedback loop "open"
(passive), which makes them terrible at rejecting 60Hz mains hum. I
simply followed the datasheet: I implemented a True Closed-Loop
Active Bias (Drive Right Leg). How it works: It measures the
common-mode signal, inverts it, and actively drives it back into
the body. The result: Cleaner data Tech stack:
ADC: TI ADS1299 (24-bit, 8-channel). MCU: ESP32 Chosen
to handle high-speed SPI and WiFi/USB streaming
Software: BrainFlow support (Python, C++, Java, C#) for those who
want to build custom ML pipelines, LSL support, and forked version
of OpenBCI GUI support This was a huge project for me. I'm
happy to geek out about getting the ESP32 to stream reliably at
high sample rates as both the software and firmware for this
project proved a lot more challenging than I expected. Let me know
what you think! SAFETY NOTE: I strongly recommend running this on
a LiPo battery via WiFi. If you must use USB, please use a laptop
running on battery power, not plugged into the wall.
Author : simontheHWguy
Score : 44 points
Date : 2026-01-05 17:46 UTC (5 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| simontheHWguy wrote:
| If you want an independent look at the specs, CNX Software and
| Hackster just wrote about the board here:
|
| https://www.cnx-software.com/2025/12/26/cerelog-esp-eeg-a-lo...
|
| And here
|
| https://www.hackster.io/news/this-open-source-eeg-board-brin...
| dang wrote:
| I'm a mod here - just wanted to let you know that I edited your
| text to fit HN conventions a bit and moved it to the top of the
| thread.
|
| Welcome to HN! I hope your project gets some good discussion.
| legitronics wrote:
| This is very interesting. I was looking into the viability of
| something like this a few months ago and started seeing eye
| watering prices and closed off ecosystems. And many gotchas when
| looking into diy, more than I could justify learning about.
| simontheHWguy wrote:
| Thank you! It was quite the project, definitely learned a lot
| from it though!!
| evanjrowley wrote:
| What is your goal with the Cerelog ESP-EEG?
|
| During my mid-teens, I got this wild idea that I could reproduce
| the experience of psilosybe cubensis by learning to mimic the
| brainwave patterns through the practice of neurofeedback. I
| didn't have an EEG, but I learned about the OpenEEG project.
| Eventually I bought an OpenEEG-based MonolithEEG[0] during a
| summer where I was fortunate enough to be in west Europe.
|
| Shortly thereafter, I realized I had no experience at all with
| electronics assembly, and the fever dream quickly evaporated. The
| MonolithEEG PCB was lost to time.
|
| [0] http://www.shifz.org/moosec/index-Dateien/Page431.htm
| simontheHWguy wrote:
| That's a great story about the Monolith.
|
| To answer your question: My primary goal right now is simply
| reliable, high fidelity data collection. However, I think
| neurofeedback is a fascinating application. I've been
| interested in eventually mixing this tech with tACS in a closed
| loop control system to train the brain to enter specific mental
| states.
|
| Regarding the MonolithEEG, it's wild to look back at that tech.
| It is a shame it was limited to 2 channels at 10 bit
| resolution, but it was a pioneer. With the ADS1299, we are now
| getting 24 bit resolution across 8 channels. That difference in
| dynamic range makes a huge difference, especially for precision
| applications like SSVEP where the noise floor really matters.
| PaulHoule wrote:
| Won't work. Those drugs blockade this receptor
|
| https://en.wikipedia.org/wiki/5-HT2A_receptor
|
| and flatline
|
| https://en.wikipedia.org/wiki/Median_raphe_nucleus
|
| and if you wanted to measure that you would have to stick
| electrodes deep into your brain, no way are you going to see
| what is going on there from the surface.
|
| Stuff I was doing last month got me interested in biofeedback
| again, I have some talent for it, I can make those mood rings
| change color at will.
|
| Most of the EEG-based biofeedback devices have three electrodes
| around the temple and cost about $300 and don't really work
| because those alpha, beta, theta and delta waves all appear in
| different parts of the brain and can't be read out of the same
| electrodes. I hear you can do better with five electrodes but
| the five-electrode headsets I see don't advertise a price.
|
| I wound up getting a Polar H10 heart rate monitor which can be
| used with HRV software
|
| https://en.wikipedia.org/wiki/Heart_rate_variability
|
| but the "biofeedback" apps I have seen so far seem to be
| breathing exercises that you could do without any hardware. I
| have electronics for EMG (muscles) and GSR (skin resistance) to
| hook up to an Ardunio and will probably try making a setup. I'm
| still looking for a soup-to-nuts answer for EEG biofeedback.
| simontheHWguy wrote:
| tFUS is a really interesting new stimulation technique for
| deep brain. Still emerging tech though so who knows where it
| will go
| ekr wrote:
| Such a striking similarity to my own path. But I was in early
| 20s-mid 20s, going through some more difficult times and after
| a lot of research and study of the nervous system and trauma, I
| came to the conclusion that neurofeedback seems like the magic
| wand that had the biggest chance to actually produce a
| transformative effect.
|
| I was experienced with soldering and electronics (mostly board
| repairs so not design), but not at a professional level.
| Initially I got an Analog Devices ADC, which they sent for free
| as I was still registered as a student at the time. I was
| trying to replicate some existing open source projects, but on
| an extremely low cost. Ultimately I got stuck in the weeds, and
| eventually gave up and just bought the ADS1299EEGFE-PDK
| evaluation board (upon which the original OpenBCI is based
| iirc). But eventually, again, postponed that, I was in the
| process of converting the LabView software to C, and to support
| real-time signal processing. After a short while I moved to the
| opposite corner of Europe and all those boards are sitting
| somewhere in my parent's attic. So the question in my mind
| still remains. Because neurofeedback does sound a bit too good
| to be true. But evidence is solid as well.
|
| I will definitely give it another go at some point when life
| gives me more slack/spare time and space.
| MrBuddyCasino wrote:
| > _I'm happy to geek out about getting the ESP32 to stream
| reliably at high sample rates_
|
| Please do.
| simontheHWguy wrote:
| The biggest challenge was the SPI communication during the
| initialization phase. I had a timing violation in the register
| set sequence that caused the IC to enter unpredictable states.
|
| Because the ESP32 is so fast, I was driving the SPI lines
| without adequate delay between bytes during configuration. The
| ADS1299 would technically "communicate" but then behave crazily
| during data acquisition. I had to go back to the datasheet's
| SPI timing diagrams and strictly enforce the timing constraints
| in firmware to get it stable. I wish SPI was a more strictly
| defined standard
| willbeddow wrote:
| Cool project! How does this compare to something like the OpenBCI
| cyton?
| simontheHWguy wrote:
| To be honest, the two biggest drivers for this project were
| Cost and Signal Integrity. 1. Cost: This was my main
| frustration. The Cyton is currently priced at 1,249.I managed
| to get the Cerelog ESP-EEG down to 299 (assembled). I really
| wanted to lower the barrier to entry for individual researchers
| and hackers who can't drop a grand on a hobby board.
|
| 2. The Bias/Noise Implementation: While we both use the same
| high-end ADC (TI ADS1299), I implemented the Bias (Drive Right
| Leg) differently. I designed a true closed-loop feedback
| system. By actively driving the inverted common-mode signal
| back into the body, the board follows the TI spec aggressively
| for helping cancel out 60Hz mains hum
|
| Regarding the analog front-end: The current version keeps the
| inputs flexible (firmware configurable) for different montages.
| However, I've found that most researchers just stick to a
| single standard montage configuration. Because the Cyton tries
| to be a "jack of all trades" for every possible montage, it
| compromises on physical filtering. For future revisions, I plan
| to trade some of that flexibility for dedicated common-mode and
| differential hardware filtering to lower the noise floor even
| further. I already had this on a previous revision prototype
| but decided to take not out for simplified testing. I'd like to
| add it back in to a future revision after some more prototype
| testing.
|
| 3. Connectivity: I'm using the ESP32 to stream over WiFi rather
| than a proprietary USB dongle. Ive been trying to get BLE SW
| working as well but noticed MAC drivers aren't the most
| friendly to my implementation.
| Curiositry wrote:
| This is a super cool project! Probably the most interesting
| neurotech hardware I've run across since OpenBCI was released.
|
| It would be great to see a side-by-side comparison of Cerelog and
| OpenBCI data from the same session/patient.
|
| A few questions:
|
| - Could you clarify which parts of the project are licenced MIT,
| which are CC-BY-SA, and which are CC-BY-NC-SA? It seemed like the
| guide and the README had more restrictive language than the
| actual license file.
|
| - What made you decide to start fresh, rather than adding the
| features you needed to the OpenBCI?
| simontheHWguy wrote:
| Thanks for the kind words! About the Side by side comparison,
| that is high on my to do list!
|
| Regarding licensing, sorry about the confusion between my repo
| init and the docs. I have updated the repo to clarify the
| distinction: Firmware & Software: MIT License. I want people to
| build whatever they want on top of the stack. Hardware
| Schematics: CC-BY-NC-SA (Non-Commercial). Why the split? Since
| I am a solo bootstrapper, I need to protect the hardware from
| low-effort commercial clones while I get the business off the
| ground. But I strongly believe in "Source Available" schematics
| so researchers and engineers can debug, learn, and modify their
| own units, hence the CC-BY-NC-SA choice for the board files.
|
| Why start fresh? It was an architecture decision. The Cyton
| uses a PIC32 + RFduino stack. I wanted to handle everything
| natively on the ESP32 for high-bandwidth WiFi streaming, which
| required a ground-up redesign. I also wanted to add onboard
| LiPo charging and the ability to experiment with different
| filter topologies. Building it from scratch helped me uncover a
| lot of subtle design constraints that aren't obvious until you
| dig into the layout.
| Curiositry wrote:
| Ah, makes sense. Thank you! I will update my blogpost with
| these clarifications.
| khr wrote:
| Thanks for making this! I'm very tempted to get one of these to
| do some ssVEP stuff.
|
| Do you have plans to make a 16-channel (or 32-channel?) board in
| the future? In my area of research, 32 channels tends to be the
| recommended minimum for studies.
| simontheHWguy wrote:
| I'm glad you like it! I actually made an ssvep pong game a
| while back with this, was kinda hard to play as the paddle was
| really small but was a cool concept demonstration. I am working
| on a video for this device to show off its capabilities with
| more depth as the current video on the site is very old.
|
| With regards to higher channel count, yes I was thinking about
| this however it will likely not be released for a few months or
| longer. The firmware/software rules change a lot when you start
| daisy chaining the ADC so dev time takes long and I need to
| reincorporate back into these software ecosystems. Hardware
| config is also a bit different.
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(page generated 2026-01-05 23:01 UTC)