Question: how heart rate function behave when display is OFF?

[Denson]

Is heart rate data stored in Fitbit device and Fitbit iOS App even if the function to switch off heart rate sensor  is included? (refer following official doc.)

https://dev.fitbit.com/build/guides/sensors/heart-rate/

I didn't figure out which behavior device would take when above function would be deployed. 

1. No heart rate data is stored in fitbit device, and so data during display OFF will be missed.

2. Heart rate date itself is stored even when display OFF, but I would not be able to get the data from sensor API. The heart rate data is able to be see in Fitbit iOS app including term of display OFF.

[Gondwana · Accepted solution]

My understanding is that the API simply allows your clockface/app to subscribe to the HR data. It doesn't actually turn the sensor on or off, so HR data is still stored, synced and available in Fitbit app, dashboard, Web API, etc.

When display goes off, I think that clockfaces are supposed to stop using sensors.

Some devices allow the HR sensor to be turned off in their Settings app.

[Denson]

Thank you for quickly reply!

So, it's better to include to switch off to get HR during display OFF in order to reduce battery consumption, right?

[Gondwana]

Yep. .stop() in display change listener.

[Denson]

Thank you!