Cobalt
The CB-91AI board seen from above, with its main components20 mmNordic nRF52840Arm Cortex-M4FprocessorCobalt LinkAntenna of thewireless linkIMUMotion: steps,sleep, gesturesLED RGBLightnotificationsBuzzerAlarms andconfirmationsMicrophoneMEMS, only listenswhile you press
The CB-91AI board seen from above
Nordic nRF52840
Arm Cortex-M4F processor
Cobalt Link
Antenna of the wireless link
IMU
Motion: steps, sleep, gestures
LED RGB
Light notifications
Buzzer
Alarms and confirmations
Microphone
MEMS, only listens while you press

Builders

An open watch, to build.

Assemble your own watch and assemble your own app. Every aspect of the Cobalt Watch project is open source. Everything on this page is there so that you can take part in the development and help bring new features to life.

On the phone side, we give you the first building blocks: Cobalt Link, the link between the watch and the phone.

The watch opened while the board is being fitted Assemble your watchHow to fit the Cobalt board in your watch.The guide $ git clone https://github.com/Cobalt-Watch/CB-91AI.git

# the reference client
firmware/tools/cobalt_link.py
# the test vectors
firmware/tests/vectors/ Code your appGet Cobalt Link and build your app on top.Where to start

Simple to fit at home.

You can replace the board yourself, at home. You only need simple tools. Allow five to ten minutes.

See the nine steps

The code

The code is on GitHub.

Cobalt-Watch / CB-91AIPublishedThe open firmware of the CB-91AI, written for Zephyr. Public repository.
Open on GitHub
firmware/watchthe watch application
firmware/libthe drivers (display, microphone, accelerometer, clock) and the logic
firmware/boardsthe board definition for Zephyr
firmware/toolsthe PC tools: flashing, updates, Cobalt Link client, measurement benches
firmware/tests/vectorsthe test vectors of the protocol and of the note format
firmware/prebuiltthe MCUboot bootloader, ready to flash
APACHE-2.0ZEPHYRC
READMELicenceHistory

The guideFirst version

Fit the board in your watch.

Before you start. You are opening and modifying a watch that you own. You do it at your own risk, and it ends Casio’s warranty on that watch.

  1. A screwdriver on one of the four screws of the watch's back.
    01
    Take off the backUndo the four screws and lift the back. Put the screws and the rubber seal where they won’t roll away.
  2. The empty case, the back, the four screws, the module with its display and the Cobalt board.
    02
    Take the module outThe module comes out in one piece, display included. The buttons stay in the case.
  3. The back of the module, with its CR2016 coin cell.
    03
    Take out the cellRemove the CR2016 and keep it. You will put it back at the end.
  4. The original green board on the left, the black Cobalt board on the right.
    04
    Separate the old boardUnclip the green board from the white plastic frame. The display stays in the frame. Here it is next to ours.
  5. The back of the original board, with a small metal contact blade being lifted off.
    05
    Move the cell contactWith the tweezers, lift the small metal blade that sits on the old board. It is the contact that touches the cell. It goes on our board, in the same place.
  6. The Cobalt board being pressed into the white frame that holds the display.
    06
    Put our board in placeComponents towards the display, gold pads towards you. It must sit flat in the frame.
  7. The module reassembled, with the cell back in place under its white film.
    07
    Put the cell backThe same way round as before, the + side towards you, under its white film. The display comes on.
  8. The module back in the case, and the back about to be put on.
    08
    Close the watchPut the module in the case, check that the seal is in its groove, then close the case and screw the four screws back in.
  9. The watch closed again, with the time on its display.
    09
    Link it to the appOpen the app and follow the pairing. The watch shows a code on its display, and you type it on the phone.

The Casio F-91W is shown here only to illustrate compatibility with our board. We make the board, not the watch.

Technical sheet

CB-91AI

The voice board in the format of the F-91W module. Kit: the board alone, you keep your watch.

Pre-order
Processor
Nordic nRF52840 · Arm Cortex-M4F
Wireless link
Cobalt Link
Microphone
MEMS PDM
Motion
Accelerometer · gestures, steps, sleep
Temperature
Built-in sensor
Display
Original LCD · ROHM BU97930 driver
Indicator light
RGB LED
Sound
Buzzer
Power
The watch’s CR2016 coin cell
Battery life
Up to six months · twenty commands a day
Size
20 mm
Updates
Wireless
Firmware
Zephyr · Apache-2.0
Phones
Android · iOS
Assembly
France

Be told as soon as Cobalt is available.

We only use your address to tell you. Privacy policy

Legal notice

Publisher

Cobalt Watch, a French simplified joint-stock company (SAS) with a share capital of Content missing euros.
Registered office: Content missing, Paris 2e, France.
Paris Trade and Companies Register (RCS): 106 218 159.
VAT number: Content missing.
E-mail: jean@cobalt-watch.com
Telephone: Content missing

Publication director

Jean de Bailliencourt, president of Cobalt Watch.

Host

Hostinger International Limited
61 Lordou Vironos Street, 6023 Larnaca, Cyprus
hostinger.com/contact

Other names

Cobalt Watch and CB-91AI are the names of our company and of our board.

The other company and product names on this site belong to their owners. We name them to say what our board and our app work with, or to compare them with our products.

Licences

The firmware of the watch is published under the Apache-2.0 licence.

The other texts, the photos, the videos and the logo belong to Cobalt Watch. For any other use, ask us.

Credits

Typefaces: Hanken Grotesk, Martian Mono, Instrument Serif and IBM Plex Sans, under the SIL Open Font License. Photos and videos: Cobalt Watch.

The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the Creative Commons 3.0 Attribution License.

Accuracy

We do our best to keep this site accurate and up to date. It can still contain a mistake, and we change it as the project moves. If you spot one, tell us.

Applicable law

This site is governed by French law.

Privacy policy

This site sets no cookie and loads nothing from other companies: no analytics, no advertising, no embedded video. So there is no consent banner. Here is the little we do handle.

Who is responsible

Cobalt Watch SAS, the company that publishes this site. For any question about your data, write to jean@cobalt-watch.com.

What we handle

WhatWhyHow longWhere
The e-mails you send usTo answer you. We have a legitimate interest in doing so.Content missingOur mailboxes, at Hostinger
Your e-mail address, if you subscribed to our newsTo send you the news you asked for. This rests on your consent.Until you unsubscribeBrevo, our mailing provider, in France
The server’s logs: IP address, date, page requested, browserTo keep the site running and secure. We have a legitimate interest in doing so.Content missingHostinger, our host
Your name and your e-mail address, if you join the waitlistTo tell you when the campaign opens, and to contact you if you asked to test. This rests on your consent.Until you ask us to remove you, or Content missingA Google spreadsheet, filled by a Google Apps Script

Content missing

Who receives it

Hostinger, which hosts the site and our mailboxes, Brevo, which sends our news, and Google, which keeps the waitlist. We don’t sell your data and we don’t pass it to anyone else.

In your browser

If you switch language with the FR / EN button, your browser remembers that choice so that you get the same language next time. This choice stays in your browser and is never sent to us. Nothing else is stored there.

Your rights

You can ask us for a copy of your data, have it corrected or deleted, object to its use, and withdraw your consent at any time. Write to jean@cobalt-watch.com: we answer within a month.

If you think we handle your data badly, you can lodge a complaint with the CNIL, the French data protection authority.

The app

The Cobalt Agent app has its own privacy policy, because it handles something else: your voice notes. It is on its own page.

Notice about Casio

We are independent. Cobalt Watch is not affiliated with Casio Computer Co., Ltd. or with any of its subsidiaries. Casio has not endorsed or sponsored our products or this website.

The names. “Casio” and “F-91W” are trademarks of Casio Computer Co., Ltd. We use them for one reason only: to say which watch the CB-91AI board is made for. When a Casio watch appears in a photo or a video on this site, it is there to show that compatibility.

What we make. The CB-91AI is an electronic board that we design ourselves. It replaces the board of a watch that you already own. We don’t make the watch, and we don’t sell Casio watches.

Modifying your watch. Fitting the board means opening and modifying your watch. You do it at your own risk. It ends the manufacturer’s warranty on that watch, and we can’t be held responsible for damage done to it while fitting the board.