Locator Tag example fails at Fast Pair Validator App test "Provisioning"

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Luca E. — Fri, 19 Dec 2025 14:40:56 GMT

Hi Hung Bui,

thanks for the fast answer, I changed the line and the "Provisioning" test passed. Perfect, thank you very much.

I was looking for that exact fix myself, but was unable to find the specific file, even though I was given the unique Log message "Key discarded (timeout)" from a certain module called fast_pair. Any tips from your experience on how to approach such a problem in the future? Could save you guys from a few questions ;)

Cheers and happy holidays to your team!

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Hung Bui — Fri, 19 Dec 2025 14:19:19 GMT

Hi Luca,
Please find the following feedback:
============

The logs from the FPV app test indicate that the smartphone does not write the Account Key to the Fast Pair Provider (nRF52 DK). The Fast Pair procedure is always concluded with the Account Key write operation, which then starts the FHN provisioning (required for the FHN extension and locator tag use case).

Our implementation expects the Account Key to be provided within 10 seconds. If the operation does not appear on time, we invalidate the temporary session key (public key) and the overall Fast Pair procedure needs to be started from scratch.

[00:00:12.943,145] <dbg> fast_pair: pairing_complete: Bonding complete
[00:00:22.943,298] <inf> fast_pair: Key discarded (timeout)

<- 10 second gap between these two logs (the write passkey operation restarts the timeout)

This is clearly what happens in the customer case. For some reason, the independent operation to read the DIS characteristic is scheduled by the Android OS, which delays the Fast Pair procedure and breaks the assumption that the Account Key write happens within 10 seconds.

It actually happens after 15 seconds, but it is rejected by our DK as the session key and the ongoing FP procedure is already marked as invalid.

[00:00:27.054,962] <wrn> fast_pair: Decrypt failed: err=-13 (Account Key)
[00:00:27.054,992] <dbg> fast_pair: write_account_key: Account Key write: res=-14 conn=0x20002810

To test this hypothesis, you can extend the Fast Pair Key timeout in the following file and line:

https://github.com/nrfconnect/sdk-nrf/blob/main/subsys/bluetooth/services/fast_pair/fp_keys.c#L28

K_SECONDS(10) -> K_SECONDS(20)

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Hung Bui — Fri, 19 Dec 2025 12:28:31 GMT

Hi Luca,
Unfortunately I haven't got a feed back from the team. The problem is that at this time most of team member already take vacation so it will be slow. Please ping me again after 1-2 weeks if you don't see any update from me.

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Luca E. — Fri, 19 Dec 2025 08:52:50 GMT

Hey Hung Bui, did you receive any new insights from the team? Is this possibly a google sided problem with the configuration of the FPV app? However it seems unlikely since I checked with two different phones each with a different Android Version.

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Luca E. — Wed, 17 Dec 2025 15:35:08 GMT

Yes that is the ADB command I was referring to. Good to know that the configuration without bonding is the right one for locator tags. I reinstalled the FPV app and ran the (three in total) ADB commands again but still the same outcome.

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Luca E. — Wed, 17 Dec 2025 15:26:17 GMT

Yes, I did follow the note.

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Hung Bui — Wed, 17 Dec 2025 15:15:23 GMT

Hi Luca,

I got another tip from the team, could you try the following:

"I haven't encountered this particular issue, but it would be good for the customer to check if they follow the network certification criteria:

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

For instance, it seems that the customer uses the Fast Pair procedure without Bluetooth pairing and bonding (logs from pairing with the FMD app). This is the recommended procedure modification for locator tag products and other device types that use the FMDN extension.

However, the FPV app still uses bonding. It seems that they might have missed to execute the following ADB command to configure their test smartphone appropriately:

For locator tags that don't create a bond during pairing, also run the following command:"

adb shell am broadcast \ -a com.google.location.nearby.apps.fastpair.validator.FLAG_OVERRIDE \ --es flag skip_bonding_for_spot_locator_tags \ --es value true \ --es type boolean \ com.google.location.nearby.apps.fastpair.validator

You mentioned that you used ADB command to not using pair, is it the same that what suggested here ?

RE: Locator Tag example fails at Fast Pair Validator App test "Provisioning"

Hung Bui — Wed, 17 Dec 2025 15:01:40 GMT

Hi Luca,

I am checking internally to see if the team can find anything wrong with this.

Btw, have you followed the note here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/samples/bluetooth/fast_pair/locator_tag/README.html#fast_pair_validator_app