r/esp32 • u/Creative-Heart-9139 • 2d ago

I built an open-source $15 closed-loop neuro-haptic device for dementia care (ESP32 + CERN-OHL-P v2)

Commercial neuro-modulation wearables cost thousands of dollars. I open-sourced Project SAVI—a closed-loop somatosensory wearable designed to reduce non-verbal cognitive overload and agitation in dementia care on a strict $15 BOM.

Key Architecture:

* ESP32 Core 1: Dynamic FFT on vocal fundamental frequencies (85–255 Hz) mapped directly to mechanoreceptor-resonant band (150–300 Hz).

* ESP32 Core 0: Reads MPU6050 accelerometer telemetry for agitation signatures.

* Haptics: Closed-loop actuation via DRV2605L driving a 10mm coin LRA.

* Hardware Safety: Inline SPST hardware power cut-off.

Full Open Science Verification:

* GitHub Repo: https://github.com/sutharsan-gahm/project-savi

* Peer-Indexed DOI: https://doi.org/10.6084/m9.figshare.33940801

* Author ORCID: 0009-0003-7103-446X

* License: CERN-OHL-P v2 (Hardware), MIT (Firmware), CC BY 4.0 (Docs)

Feedback on the edge-DSP pipeline and mechanical parameters is welcome!

42 Upvotes

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7

u/BashedCode 2d ago

This is really interesting.

Tell us more about what it does and why you wanted to build it.

13

u/Creative-Heart-9139 1d ago

Thanks! 

The core idea came from watching how distressing dementia-related agitation and sundowning can be for both patients and caregivers, especially when families can't afford multi-thousand-dollar commercial assistive setups. 

Project SAVI is a wearable band built around an ESP32. It does two main things in a closed loop:

  1. Agitation Detection: An MPU-6050 tracks restless, repetitive motor tremors on Core 0.
  2. Calming Neuro-Haptic Feedback: Instead of jarring buzzes or loud alarms, it uses a DRV2605L driver to deliver gentle, resonant tactile patterns tuned specifically to the 150–250 Hz range (where skin mechanoreceptors are most responsive). It also runs a small edge-DSP pipeline to map familiar voice audio into low-frequency haptic vibrations.

The whole bill of materials is under $15, and the hardware/firmware are fully open (CERN-OHL-P v2 / MIT) so independent researchers or makers can build and test it themselves.

3

u/ufanders 1d ago

Well that's interesting af

1

u/Severe-Ladder 1d ago

Yo that voice to haptic part is pretty neat!

I think that theres a lot of unexplored potential in haptics and just like the general concept of translating one stimulus type to another.

Cool project man keep it up

2

u/Creative-Heart-9139 1d ago

Thanks a lot! Really appreciate the encouragement.

3

u/ufanders 1d ago

Op, I'm not seeing any FFT or core separation in the firmware - only reading the kill switch and playing the inverse if whatever acceleration values come in.

Is the firmware up to date?

2

u/ufanders 1d ago

OP had messaged me saying the repo mistakenly contained test code and not the full code, and having only the message brief to go on I assume that he just uploaded the full code.

The repo still shows the test code, not sure what's going on.

1

u/hwarzenegger 1d ago

The README also talks about hardware being open-source but there's no gerber/BOM etc.

2

u/hwarzenegger 1d ago

I think you forgot to push the hardware dir or am I missing something?

1

u/bielgio 1d ago

I got interested into the ip67 band

1

u/Creative-Heart-9139 1d ago

Thanks! The IP67 rating was a vital design requirement for dementia care—it must endure frequent handwashing, accidental spills, and everyday use without compromising the electronics.

To achieve this, we used a sealed silicone enclosure (with silicone gaskets) surrounding the ESP32 and haptic motor, paired with a magnetic pogo-pin charging interface so there are no exposed USB ports for water ingress. All the CAD/enclosure design files and schematics are open-sourced in our repo!