Find TxPower on iOS Bluetooth Peripheral

Question

I am building an iOS app (in Swift) that acts as both a Core Bluetooth peripheral and central. I need to determine the txPower of the peripheral but I don't necessarily need to send it to the other device's central (though that would be great); I would be happy just determining the txPower of the peripheral on the sending device itself.

I know that I can determine txPower from Manufacturer Specific Data, but I have not been able to figure out how to read my device's Manufacturer Specific Data, and the advertisingData my central is picking up only includes the peripheral's UUID, not the Manufacturer Specific Data.

This is how I set up my peripheral:

peripheral = CBPeripheralManager(delegate: self, queue: nil)
myService = CBMutableService(type: CBUUID(string: "109F17E4-EF68-43FC-957D-502BB0EFCF47"), primary: true)
peripheral.addService(myService)

This is how I set up my central:

centralManager.scanForPeripheralsWithServices([myCustomServiceUUID], options: nil)

Then in peripheralManagerDidUpdateState:

    if peripheral.state == CBPeripheralManagerState.PoweredOn {

        self.peripheral.startAdvertising([CBAdvertisementDataServiceUUIDsKey: [myService.UUID] ])}

... in centralManagerDidUpdateState:

    if central.state == CBCentralManagerState.PoweredOn {

        centralManager.scanForPeripheralsWithServices([myCustomServiceUUID], options: [
            CBCentralManagerScanOptionAllowDuplicatesKey : NSNumber(bool: true)
            ])}

And the resulting advertisementData NSDictionary in didDiscoverPeripheral delegate is:

["kCBAdvDataServiceUUIDs": (
"109F17E4-EF68-43FC-957D-502BB0EFCF47"), "kCBAdvDataIsConnectable": 1]

Again, any solution that allows me to add the Manufacturer Specific Data in my peripheral's advertising packet, or allows me to read the peripheral's Manufacturer Specific Data or txPower on the sending device would be truly awesome. Thanks so much in advance!

Answer 1

From my experience, it is not possible to get the TX power level or any manufacturer data at all from other iOS peripherals using the CoreBluetooth API, because it is stripped away from the scan result you receive on the didDiscoverPeripheral callback. You can however get the RSSI value of the peripheral, maybe you can use that depending on what you want to achieve.

I'm not sure how you would want to determine the TX power level from the manufacturer data though. The BLE specification defines a seperate characteristic for it.

Hope this helps!