Disable and Reenable Locator Tag FMDN frame after provisioning

[BIPIN]

Hi,

I am working on Google fast pair locator tag using NCS sample code. For final product, we need one function in device for certification that is to disable and reenable FMDN frame (locating functionality) using button action. Can you guide me how can I do it in sample code example. Below guideline from Nordic given this option by direct power ON/OFF switch. I want this without power ON/OFF and using button press pattern. 

https://docs.nordicsemi.com/bundle/ncs-3.0.2/page/nrf/samples/bluetooth/fast_pair/locator_tag/README.html

Regards,

Bipin Patel

[Amanda Hsieh]

Hi, 

we need one function in device for certification that is to disable and reenable FMDN frame (locating functionality) using button action.

What certification do you mean? Could you provide the document or link? Do you mean the Fast Pair Validator app on the Android device? If so, please refer to the steps in the Testing/Fast Pair Validator app section. 

Regards,
Amanda H.

[BIPIN]

Hi Amanda,

I am talking about UL certification. There are two kind of tests. Automated (Using Fast Pair Validator app) and Manual (Using Find Hub app).  I am talking about one of test from Manual self test. Below is a link for that and sharing screen shot for your reference. By this test Device should stop sharing its location and also reenable it based on button action.

https://developers.google.com/nearby/fast-pair/early-access/fmdn-certification-guideline#manual-tests

Regards,

Bipin Patel

[BIPIN]

Hi Amanda,

Now I can disable and reenable FMDN frame. But one question regarding the clock synchronization.

On power up, Fast Pair not discoverable advertisement started due to clock sync enable. Can you please explain me how clock sync occur and this not discoverable frame disabled. I have tried to perform clock sync test as per below link but I am not getting below debug log message. Is clock sync happened with only with owner phone or other surrounding phone can also do it?

FMDN: clock information synchronized with the authenticated Bluetooth peer

https://docs.nordicsemi.com/bundle/ncs-3.0.2/page/nrf/samples/bluetooth/fast_pair/locator_tag/README.html#clock_synchronization

Regards,

Bipin Patel

[BIPIN]

Hi Amanda Hsieh 

Can you please help with above question?

Regards,

Bipin Patel

[Amanda Hsieh]

HI, 

This power-up behaviour is in line with the FHN specification: 

https://developers.google.com/nearby/fast-pair/specifications/extensions/fmdn#fast-pair

 

After a power loss, the device should advertise non-discoverable Fast Pair frames until the next invocation of read beacon parameters.

 

The clock synchronization must be performed by the owner's phone, as the owner's Account Key is used to authenticate this Beacon Actions command

[BIPIN]

Hi Amanda,

I have below questions if you can help.

1) If device advertise non-discoverable fast pair frames in case of power loss or restart for clock synchronization and there is no owner phone around then will it continue advertise on-discoverable forever till clock sync occur? Is any timeout for this on-discoverable frame to save battery life? asking this because if on-discoverable advertisement at 100ms interval takes around 120uA and if no clock sync happen then it can drain battery early.

2) Once in 24 hours clock sync logic for non-discoverable fast pair frames is at device side or android phone side?

3) Can we modify it by some way just for fast testing of clock synchronization?

4) If owner lost tag and tag HW is restarted or power cycle for some reason and clock drift occurs. In this case clock sync will not happen as owner phone will be not available so in such cases how clock sync happen and the owner can get location?

Regards,

Bipin Patel

[Amanda Hsieh]

Hi, 

Ad 1. There is no timeout - this is a critical feature to prevent the locator tag from losing synchronisation with the owner device permanently. If you have any scheduled reboots (e.g., during the DFU), you can refrain from starting not discoverable advertising after such a scheduled reboot

 

Ad 2. Don't really understand the question here.

 

Ad 3. Yes, you can disable auto clock synchronisation on reboot and manage it on your own:

CONFIG_BT_FAST_PAIR_ADV_MANAGER_USE_CASE_LOCATOR_TAG_CLOCK_SYNC_TRIGGER=n

https://github.com/nrfconnect/sdk-nrf/blob/main/subsys/bluetooth/services/fast_pair/adv_manager/loc…

(see how the clock sync trigger is managed with the CONFIG_BT_FAST_PAIR_ADV_MANAGER_USE_CASE_LOCATOR_TAG_CLOCK_SYNC_TRIGGER set to y)

You can create the clock sync trigger at the application level and manage it as needed.

 

Ad 4. If clock drift is really long (e.g., more than 24 hours), the locator tag won't be mapped correctly with the owner account, and the location updates will not show up for it

[BIPIN]

Hi Amanda,

Thanks for reply.

Let me clarify my question 2. Please look on below screen shot. It says "The Android device uses a throttling mechanism to prevent the beacon clock synchronization from happening more than once every 24 hours."  Is this 24 Hrs time is configured to phone or locator tag? Can we reduced this interval of 24 hrs for fast synchronization of clock and to save battery life so non-discoverable advertisement can be stopped as soon as possible? 

Regards,

Bipin Patel

[Amanda Hsieh]

Ad 2. It is the internal configuration of the Android OS. It is controlled by the Google team, and you cannot change it

[BIPIN]

Hi Amanda,

Thanks for clarity.

Regards,

Bipin Patel