FRESH

Hacker News

Show HN: ESPectre – Motion detection based on Wi-Fi spectre analysis

203 points by francescopace

by francescopace

5 subcomments

Fun fact: I’m working on turning ESPectre into a Wi‑Fi Theremin (the musical instrument you play by moving your hands near an antenna).
The idea of “playing” by simply moving around a room sounds a bit ridiculous… but also kind of fun.
The key is the Moving Variance of the spatial turbulence: this value is continuous and stable, making it perfect for mapping directly to pitch/frequency, just like the original Theremin. Other features can be mapped to volume and timbre.
It’s pure signal processing, running entirely on the ESP32. Has anyone here experimented with audio synthesis or sonification using real-time signal processing?

by roger_

1 subcomments

Been working on this very idea casually for couple years with ESP-IDF and I could never get the statistical signal processing just right (by my definition). Things I've tried: adapting filtering (LMS, Kalman), kernel methods (NEWMA, MMD), detectors (CUSUM, GLR), dimensionality reduction (random projection, online PCA), whitening, etc.
I use a single ESP32 in STA/AP mode which sniffs ACK packets with a specific destination mac, which come from any server on my WiFi network (uses a special sniffing mode IIRC). This way I can receive regular CSI packets originating from a fixed location and doesn't need another device running.
I'll have to look at this code, maybe I just overlooked the obvious or my requirements were too high!

by jstanley

1 subcomments

> The system does NOT use Machine Learning, it relies purely on Math.
You may be surprised to find out how machine learning works!

by tetris11

1 subcomments

Amazing stuff!
Am I right in understanding that only a single ESP32 device is needed (plus a router)?

by Gys

3 subcomments

Interesting! Are you familiar with tommysense.com? I think it doing something similar? Did not yet have time to try it.

by sert_121

1 subcomments

This jogged some memories! Was working on something that used radio waves to detect objects and humans ~5 years ago, I see that we've come a long way since then.
One of our goals(abandoned) was to also extend to wifi routers, so I am excited to see continued interest in this space!
https://www.sensorsportal.com/HTML/ST_JOURNAL/PDF_Files/P_32...

by sgc

1 subcomments

I see you have done a fair amount of work to document calibration for various scenarios. Have you tried to calibrate to ignore cats? Can you prioritize different algorithms to focus on size rather than speed of movement?
Also, I use an ebay purchased ruckus router designed for commercial settings. Will the stronger signal and beam forming from the router provide better or worse performance, or is that mainly down to the esp32?

by TGower

1 subcomments

Using two ESP32-S3 modules you can get ~6000 packets per second with CSI data. I'm using this as a cheap replacement for specialty high-G gyroscope modules, but it could see use for this type of motion detection as well.

by acl

1 subcomments

by culi

1 subcomments

The surveillance implications for this technology are fascinating and frightening.

by raggi

1 subcomments