BLE scan not finding Android advertisement unless initially paired

Former Member over 5 years ago

Hello all!

I'm running into an issue where my Android service advertisement isn't being detected by my Fenix 5x watch unless I manually pair the watch and Android device. To test this, I'm using the NordicThingy52 sample app on my watch and the nRF Connect app on two Android devices - one that has been paired with the Fenix, and one that has not. On the Android device where the Fenix has been paired, I can create almost any Advertiser in the nRF Connect app and then shortly after starting the advertisement, I am able to see my device advertisement in the NordicThingy52 app on the watch. However, if I run the same (or any other) Advertiser profile on the Android device that has never been paired with the watch, I am unable to see the advertisements on the watch. Oddly enough, even though I cannot see the advertisement on the watch, I am able to see it on the other Android device.

If I select pair phone on the watch and pair it in the Android Bluetooth menu, all of my advertisements that were previously unavailable are now received by the watch. After pairing, I can unpair and the watch is still able to receive advertisements as I would expect should always be the case. I am getting advertisements from other Bluetooth devices in my home so I know that I shouldn't need to pair with the device to receive the broadcasts. Anyone have any idea what might be going on?

Just to be clear, I've confirmed this same issue occurs with a Fenix5x, a Fenix6x pro, and two separate Android devices - A Pixel XL and Galaxy S7.

0 jim_m_58 over 5 years ago

I've never tried this - Just pairing to HR, the thingy52, Raspberry pi, etc, but if I recall,don't you have to be in connections>bluetooth for the phone to send advertisements (it make it "visible" to other devices?

If you are already paired to the phone, maybe a device won't see it.

0 Former Member over 5 years ago in reply to jim_m_58

jim - thanks for the quick response.

To clarify, I am able to see the BLE advertisements if I've already paired with the phone. I am not able able see them if I have not paired with the phone at least once. After the initial pairing, I can see the advertisements without issue regardless of whether or not I am paired with the phone.

I'm not sure what you mean by being in connection>bluetooth. Are you saying that the device needs to show up under that section on the phone? Or I need to have physically navigated to that menu on the phone? AFAIK, I can send advertisements from the phone with the only requirement being bluetooth turned on.

0 jim_m_58 over 5 years ago in reply to Former Member

On android, under settings>Connections there is Bluetooth. I seem to recall the phone is only advertising when you are on the screen (where you are looking to pair with something) and it's not visible at other times.

On the phone, what would you use for GATT?

0 Former Member over 5 years ago in reply to jim_m_58

I'm using the nRF Connect app to advertise on my Android device for the test. I'm fairly certain that the connect app is using BluetoothLeAdvertiser under the hood.

0 jim_m_58 over 5 years ago in reply to Former Member

could be that the advertisement isn't set with LE Discoverable mode.

See https://www.silabs.com/community/wireless/bluetooth/knowledge-base.entry.html/2017/02/10/bluetooth_advertisin-hGsf

So it's for BT and not BLE.