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May 23, 2020


RebbleOS is an open-source reimplementation of the firmware for the devices formerly manufactured by Pebble Technologies, Inc. The firmware is based on FreeRTOS, and aims to be binary-compatible with applications that were written for the original Pebble OS, as well as radio-compatible with smartphone applications that are designed to work with Pebble.


Supported Feature Matrix

Feature TinTin (Pebble 1) Snowy (Time, Time Steel) Chalk (Round) Silk (Pebble 2) Asterix Vla-52840
Display: N Y N N Y Y
Flash: Y Y Y N Y Y
Buttons: Y Y Y N Y Y
Accel: N N N N N N
Gyro: N N N N N n/a
Magnetometer: N N N n/a N n/a
HRM: n/a n/a n/a N n/a N
Vibrate: N Y Y N N N
Backlight: Y Y Y N N N
Power Management: N N N N N N
Bluetooth: N Y (Alpha) N N WIP WIP
Overall (%): 5% 20% 10% 0% 15% 15%


Q: Do you have a list of work to do?

A. Sadly not yet. Get the code up and running, and see what is obviously missing that you would like to do. Check with the channel first on what we have We also have a list of issues

Q: Can anyone do this?

A. Sure. Make a change to the code, docs etc and submit a pull request

Q: How much works?

A. Basic hardware and some apps will work ok. Bluetooth is coming along slowly. We are writing the core functions at the moment.

Q: Can I run it on hardware?

A. Snowy, yes. But it's experimental and whatnot. Be careful. We are not liable for eaten dogs.

Q: Where is the FPGA. It complains when I build.

A. It's pinned in the Discord channel for download. Click the pin icon on the top right and you should see a post with two links to .bin files.


RebbleOS needs your help! This section discusses what you need to know to get started working on the project.


RebbleOS currently can be built for snowy (Pebble Time and Pebble Time Steel) and tintin (Pebble and Pebble Steel). To build RebbleOS, follow these steps:

  • Obtain a checkout of the RebbleOS source code. Ensure that you have also checked out the submodules required to build the resource tree: git submodule update --init --recursive
  • Create a if your cross-compiler is in an unusual location. For instance, if you have the SDK installed in /home/me, add the following line to your PEBBLE_TOOLCHAIN_PATH=/home/me/Pebble/SDK/pebble-sdk-4.5-linux64/arm-cs-tools/bin. For more information on variables, consult the Makefile.
  • Build the firmware: make
  • If you wish to run the firmware in qemu, copy the resources necessary into Resources/. Take a look at Utilities/ for more information on that.
  • To run the firmware in qemu, try make snowy_qemu.

Building on Debian Stretch

Building on Arch Linux/Parabola

Building on macOS

Building on Windows

If you wish to build firmware to run on your device, you may also wish to consider a script like Utilities/ Running RebbleOS on hardware is currently out of scope for this document.

You need the snowy_fpga.bin and chalk_fpga.bin files to compile on their respective firmwares. They can be found on the #firmware channel in the Rebble Discord.

Code structure

(This section is, admittedly, somewhat aspirational. Do not be surprised if code within RebbleOS does not necessarily conform to this structure yet!)

RebbleOS is composed of four major components: the hardware abstraction layer, the core operating system, the PebbleOS compatibility layer, and system applications. We break down these components as follows:

  • Hardware abstraction layer. This subsystem provides a unified interface for the rest of the system, and abstracts away platform-specific elements. The HAL lives in the directory hw/; symbols that the HAL exports to the rest of the system are prefixed with hw_. The main entity that the HAL works on is a "platform"; for an example, take a look at hw/platform/snowy/ A platform depends on various chip components, and potentially other driver components; it exports a platform.h that includes all defines that the rest of the system may need. The HAL is, in theory, independent of the rest of the OS; it does not call into the rest of the system other than through debugging mechanisms and through callbacks that it is provided.

  • Core OS. This subsystem provides basic services that any smartwatch OS, even if not implementing a Pebble-like API, might need. HAL accesses are marshalled through concurrency protection; higher-level power management takes place; and, flash wear leveling and filesystem management happens in the core OS. The core OS lives in rcore/, and symbols exported from the core OS are prefixed with rcore_. It calls on FreeRTOS, which lives in FreeRTOS/.

  • Pebble compatibility layer. The core OS provides basic isolation between threads and framebuffer management primitives, but the Pebble compatibility layer provides higher level operations, like Pebble-style layers, input management and routing, and UI services. The Pebble compatibility layer lives in rwatch/, and symbols exported from it are prefixed with rwatch_. (Functions that are exactly analogous to Pebble APIs may be named with their exact name.)

  • System applications. We'll, uh, get there when we have some. Yeah.

Code style guide


  • DRV_LOG for hw
  • KERN_LOG for rcore drivers
  • SYS_LOG for rcore/rwatch processes
  • APP_LOG is for logging from apps, internal or otherwise

No style wars.

Do what's best.

Reuse and contact

RebbleOS is an open-source project licensed (primarily) under a BSD-style license. For more information, please see the LICENSE and AUTHORS files. Additionally, contributors and members of the RebbleOS community are expected to abide by our code of conduct; for more information on that, please see the file. Reuse of this project is not only permitted, but encouraged! If you do something cool with RebbleOS, please get in touch with us. The easiest way to do so is through the Rebble Discord server, channel #firmware. We look forward to meeting you!


open source operating system for low-power smartwatches



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