I've been stuck on this problem for quite some time and couldn't find a clear answer anywhere, so posting here.

Here's my setup:

- Android app acts as a scanner

- Multiple BLE sensors are placed in the same room

- When a sensor receives a SCAN_REQ from the phone, it starts advertising its data

- App receives that advertisement, parses it and displays it

The problem is — when the phone starts active scanning, SCAN_REQ goes to every nearby scannable sensor at the same time. All sensors trigger at once. I need only one specific sensor to trigger at a time.

What I tried:

1. ScanFilter with specific MAC address:

I passed the target sensor's MAC in ScanFilter like this:
<

val filter = ScanFilter.Builder()
    .setDeviceAddress("XX:XX:XX:XX:XX:XX")
    .build()
val settings = ScanSettings.Builder()
    .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
    .build()
bluetoothLeScanner.startScan(listOf(filter), settings, scanCallback)>

But I'm not sure if this actually restricts the SCAN_REQ at the hardware level or just filters results on the app side.

2. Sensor-side whitelisting:

Tried making the sensor respond only to my phone's MAC. But Android's BLE Advertisement API randomizes the MAC address periodically — so the sensor can never maintain a reliable whitelist.

3. GATT connection:

Not suitable for my case. Need advertisement-based communication only — no connections.

My questions:

1. Does ScanFilter with setDeviceAddress() restrict SCAN_REQ at the controller level or only on the app side?

2. Is there any Android API to control which device gets the SCAN_REQ?

3. Can we set a fixed public MAC when using Android BLE Advertisement API?

4. Is sensor firmware-side filtering the only real solution?

I believe this is a hardware/OS level limitation but would love a confirmation from someone who knows BLE internals well.

Thanks!