Frequently asked questions

When can I install PaceOS?

We do not know yet. PaceOS already runs on a real watch, but only as PaceOS live: booted into RAM from a computer over USB, with nothing written to the watch. Permanent installation is not done yet, and the browser installer is not published yet. A locked bootloader (unlocked: no) refuses booting from RAM; the watch PaceOS runs on has an unlocked one. There is no guarantee that this works on every watch. The status and the planned path are on the Install page.

Which phones and browsers work with PaceOS Connect?

Over Bluetooth (the page at paceos.lukaskovar.com) only browsers with Web Bluetooth work:

• Chrome and Edge on Windows, macOS, ChromeOS and Android – yes.
• Chrome on Linux – only after enabling chrome://flags/#enable-experimental-web-platform-features.
• iPhone and iPad (any browser), Firefox and Safari – no, they have no Web Bluetooth.

After a page reload you pick the watch in the browser again. The first time, the browser pairs with the watch using a 6-digit code shown on the watch.

Over the USB cable or Wi-Fi any ordinary browser works, without Web Bluetooth: the watch serves the Connect page itself at http://172.16.42.1/connect/ (cable) or at the address shown in Menu → PaceOS Connect (Wi-Fi). Over Wi-Fi it is reachable only while that screen is open on the watch.

The phone for notifications and music is an Android phone with the Gadgetbridge app (see the next question). There is no such app for the iPhone.

Does Gadgetbridge work?

The watch speaks the Bangle.js protocol, which Gadgetbridge (a free Android app) already supports. Through it the watch gets notifications, calls, the time and time zone, and the weather for the clock face; it controls the phone's music and reports its battery. The phone can also find the watch (it vibrates), and the watch can make the phone ring (Menu > Phone > Find my phone).

The last 20 notifications stay on the watch (Menu > Phone, or tap the envelope on the clock face) and can be read in full, dismissed (on the phone too) or answered with a quick reply where the app allows it (set the replies in Connect). A call gets its own page: reject, accept or mute; the button rejects. The list is kept in memory only – never written to the watch's storage or its log.

Notifications during a run follow a policy: by default calls and texts only; the watch counts the rest and tells you after the run. During quiet hours, notifications outside a run neither vibrate nor light the screen.

The protocol is tested with messages in Gadgetbridge's format and in the emulator. Bluetooth on the watch works (PaceOS Connect from Chrome), but Gadgetbridge on a phone has not been tested yet. The pairing steps will be added after that.

Gadgetbridge does not transfer runs; they go to Strava and intervals.icu over Wi-Fi, or you download them in Connect.

How do Strava and intervals.icu work?

The watch uploads runs itself over Wi-Fi, with no phone and no PaceOS server in between: after a run is saved, or with Menu → Sync now. Each run is uploaded once.

• Strava: create your own app at strava.com/settings/api and enter its Client ID, Client Secret and a refresh token with the activity:write scope in Connect (Accounts). PaceOS has no server of its own to hold the login for you.
• intervals.icu: your athlete ID and API key from Settings → Developer Settings. The watch also fetches the workouts planned for the next 8 days; they appear in the Workouts menu by name and day.

You can also download the FIT files by hand (Connect → Runs) and upload them anywhere, Garmin Connect for example.

The uploads are tested against mock Strava and intervals.icu servers. They will be verified with real accounts in the field test.

How long does the battery last?

Not measured on the watch yet. The manufacturer quotes about 11 days as a watch and 35 hours with GPS for the stock system. Whether PaceOS gets close will only be known from measurements on the watch.

The only measurements so far are the ones an emulator allows: on the clock face the system suspends between minutes and is asleep 95 % of the time. That is processor behaviour in the emulator, not current draw – the emulator cannot measure the display, GPS or radios.

What saves battery already: Wi-Fi stays off until you switch it on; GPS and the heart-rate sensor run only during a run and on the GPS screen (without a start they switch off after 5 minutes); the backlight comes on only after a press, a touch or a notification. Still open: whether the processor can also sleep between GPS fixes during a run.

Menu → System shows the measured drain and an estimate of the battery life once the charger is unplugged.

Can I go back to the stock firmware?

That is the plan. Before anything else, the watch's whole storage is backed up and the backup verified. The test boot from RAM writes nothing to the watch, and a restart brings back the stock system. Installing will be offered only with a tested way back from the backup.

On a real watch, the backup and the RAM boot with a restart back to stock have been tested. Restoring from the backup has not.

Is it safe?

Today there is nothing to install, so nothing can happen to your watch. Changing a watch's system is always a risk, though – hence the backup, the RAM boot and the checks before each further step. Once installing is possible, it is at your own risk.

What PaceOS does for security:

• Updates are signed. Before writing, the watch checks the signature, the model, that the version is newer, and every checksum. Even a server someone has taken over cannot install anything on the watch.
• Wi-Fi passwords and the Strava and intervals.icu tokens go into the watch one way only: Connect can write them but never read them back.
• The watch's interface refuses any foreign web page. Over Wi-Fi it is reachable only while the PaceOS Connect screen is open.
• A browser pairs over Bluetooth with a code shown on the watch, and the link is encrypted.

Not there yet: the data on the watch is not encrypted (someone with the watch and a computer can read the runs), and the bootloader does not check the kernel's signature.

Does PaceOS work on other watches?

No. PaceOS is only for the Amazfit Pace (A1602/A1612).