New Part Day: A Hackable Smart Ring

A closeup of the ring, inner electronics including a lit green LED seen through the inner transparent epoxy, next to the official app used to light up the LED for a demo.

We’ve seen prolific firmware hacker [Aaron Christophel] tackle smart devices of all sorts, and he never fails to deliver. This time, he’s exploring a device that seems like it could have come from the pages of a Cyberpunk RPG manual — a shiny chrome Bluetooth Low Energy (BLE) smart ring that’s packed with sensors, is reasonably hacker friendly, and is currently selling for as little as $20.

The ring’s structure is simple — the outside is polished anodized metal, with the electronics and battery carefully laid out along the inside surface, complete with a magnetic charging port. It has a BLE-enabled MCU, a heartrate sensor, and an accelerometer. It’s not much, but you can do a lot with it, from the usual exercise and sleep tracking, to a tap-sensitive interface for anything you want to control from the palm of your hand. In the video’s comments, someone noted how a custom firmware for the ring could be used to detect seizures; a perfect example of how hacking such gadgets can bring someone a brighter future.

The ring manufacturer’s website provides firmware update images, and it turns out, you can upload your own firmware onto it over-the-air through BLE. There’s no signing, no encryption — this is a dream device for your purposes. Even better, the MCU is somewhat well-known. There’s an SDK, for a start, and a datasheet which describes all you would want to know, save for perhaps the tastiest features. It’s got 200 K of RAM, 512 K of flash, BLE library already in ROM, this ring gives you a lot to wield for how little space it all takes up. You can even get access to the chip’s Serial Wire Debug (SWD) pads, though you’ve got to scrape away some epoxy first.

As we’ve seen in the past, once [Aaron] starts hacking on these sort of devices, their popularity tends to skyrocket. We’d recommend ordering a couple now before sellers get wise and start raising prices. While we’ve seen hackers build their own smart rings before, it’s tricky business, and the end results usually have very limited capability. The potential for creating our own firmware for such an affordable and capable device is very exciting — watch this space!

We thank [linalinn] for sharing this with us!

34 thoughts on “New Part Day: A Hackable Smart Ring

          1. Small was meant in a generall way not as “not fitting small” :)

            The size 11 is just a little to big for my kinda big hand so now i orderen a size 10 pair which should fit better. to give an idea.

            That ring is crazy small for what it can do, with now tested 5 days of battery runtime

  1. Awesome. Not just OpenSource…but OpenData.
    Do you/anyone know of a smart ring with this level of hackability that ALSO has vibration.
    I talk too fast and want gadget bridge bridging to the smart right and the ring gathering SpO2 + HR back to an app on my phone (androwish) that is not only measuring voice pitch but also the HR/SpO2 and when it realizes I’m going to fast to be an effective communicator or talking too long…then the app will vibrate the smart ring. 1st it’s a warning, then it could send pacing 1 every second? that I would know to slow down breath, …
    Assistive technology.

    So any hackable ring with vibration?

    1. Vibration is a BIG ask on something this compact.

      Frankly, being able to fit enough battery in this volume to get a day of use from it is astonishing.

      You might be able to make one that could give you a tiny shock as haptic feedback. That could physically fit in the space. But it would probably not work within reasonable battery constraints unless it only needed to go off 2-3 times in an emergency.
      Or maybe once it goes off it no longer matters if the ring runs out of charge? I could see that being on the very far end of useful for something like a medical emergency alert or something.

      1. Fingers are very sensitive, so you’d need orders of magnitude less power than a vibrator that has to be felt in a bag or pocket. I suspect an electric shock could be detectable at very low power with some experimentation, although it might be tricky to account for variations in ring orientation and skin conductivity.

        It would also be worth trying a piezo vibrator, or perhaps something involving a tiny loop of memory wire that pokes you for attention.

        Of course, at this scale, adding even the simplest hardware would be very challenging unless the manufacturer did it.

        1. It’s possible that one of the mems microphones that are coming to market might be able to do this, just plug its sound hole. I’m not super familiar with them, though, and don’t know if there’s one that’s tiny enough.

          I was thinking a curved mems device would be great, and while theoretically possible, it would require basically a whole new packaging scheme, which would be cost prohibitive until you get into probably tens of millions of devices. Maybe there’s a clever solution that I don’t see, though.

          Googling shows *just* such a device in a research paper!! So I take it all back, “just” requires tons more engineering effort to further miniaturize (it would currently take up most of the Ring’s perimeter), strengthen Haptic forces (discrimination test were done while the subject pinched the bare actuator, it would need a lot more force when buried in a ring and not pinched), and industrialize it. see “Haptic MEMS based on novel ultra-thin MEMS Technology”, Kobayashi and Takeshita, AIST 2021.

          Maybe the ring is thick enough that a planar device with a more traditional MEMS manufaipricess could be used. Hopefully this thing takes off, stimulates the maker, and someone develops a solution. It definitely won’t be easy, though.

    2. Get the “adult toy” industry interested?
      Plenty of capitol, there, to fund something that makes a ring buzz. ;)
      Possibly adapt/hack an existing item with the ring shape?
      Perhaps adapt to a bracelet or watch band sort of gadget.

    3. I feel like it’s not really necessary to cram everything into the ring. It’s perfectly valid to have a larger device somewhere else that does the vibration and syncs with the ring over ble.
      Although then that device could also do the tracking so not even a ring needed 🤔
      An ankle strap might work as a hidden device.

    4. I suspect using your phone to do the vibration would be more practical. You’d just need a pattern that was recognizable for this specific notification so you’d know not to look at your phone.

  2. I have a ‘hack’ for when a ring is a bit large for your fingers: apply some hot glue. Yes, it’s a bit tricky as you need to ‘flatten’ it before it becomes solid. This method worked for me on a ring that was a bit too large. Don’t worry the hot glue wont be permanent there

  3. When the oura ring was launched, I remember thinking “man this is amazing tech, but I don’t think it’ll become affordable anytime soon”

    Lo and they’re 20$ now

  4. why not revert this ring?
    I need encrypt text. Simple read the barcode (hanging ring over paper with barcode) and encrypt (read)/decrypt data simple 8 bit (octet) diode screen? Simple way read data or encrypt it without computer. Meybe in future read data directly from text or 2d code or…. simple way. Big (size) | when 1 and | for 0 I can siple write any data on paper using only pen or pencil. fat line and normal line. Add xor on end line or crc.
    Simple idea and I can send without computer solid encrypted message.Just put aes+twofis+eliptic mathematic curve (like veracrypt) data and I can storage my password on paper.

  5. I am disappointed that the company does not provide prices for this item on their web page. Nor, for that matter, on any of the dozens of smart watches they sell. “I’ll tell you the price after you’ve given lots of contact information” seems a prelude to having one’s phone number and email passed around for spammers to enjoy.

    Might reconsider when they put up actual prices.

    1. Fairly certain their website is for businesses to get quotes for bulk orders. Try places like AliExpress for consumer purchases, just got mine on special for $12 AUD

  6. Also noticed that the Colmi app is absent from Mac app store as well as the Google Play store. Would it be unreasonable to ask if that is because the app contains malware or spyware? If it is not unreasonable, then is there a compatible app that is safe? Something on github or linux?

  7. Does anyone have any idea on how to access IO for the accelerometer and hr/o2 sensor? I don’t see how any hack can be useful without that data. I assume looking at the existing code would be useless without some way to reverse engineer it. In other words, what can be done with this hack?

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