Scanning for Peripherals
Once the CBCentralManager is up and powered on, you can create a function that scan for peripherals around us.
Create a function called startScanning. Call the method scanForPeripherals(withServices:).
This method scans for peripherals that are advertising services. Now since the unique identifier is set up, add that reference to the method.
func startScanning() -> Void {
// Start Scanning
centralManager?.scanForPeripherals(withServices: [CBUUIDs.BLEService_UUID])
}
Now add the startScanning() function to the centralManagerDidUpdateState to scan as soon as the app opens.
extension ViewController: CBCentralManagerDelegate {
func centralManagerDidUpdateState(_ central: CBCentralManager) {
switch central.state {
case .poweredOff:
print("Is Powered Off.")
case .poweredOn:
print("Is Powered On.")
startScanning()
case .unsupported:
print("Is Unsupported.")
case .unauthorized:
print("Is Unauthorized.")
case .unknown:
print("Unknown")
case .resetting:
print("Resetting")
@unknown default:
print("Error")
}
}
}
When you run your app, your device will start scanning for peripherals.
Discovering Peripherals
Now that scanning is started, what happens when a peripheral is discovered?
Every time a peripheral is discovered, the CBCentralManager will notify you by calling the centralManager(_:didDiscover:advertisementData:rssi:) function on its delegate.
This function provides the following information about the newly discovered peripheral:
- The discovered peripheral is recognized and can be stored as a CBPeripheral.
- The discovered peripheral has stored advertisement data.
- The current received signal strength indicator (RSSI) of the peripheral, in decibels.
Since you are interested in connecting to one peripheral, create an instance of a peripheral.
private var bluefruitPeripheral: CBPeripheral!
Call the didDiscover function. This tells the delegate the central manager discovered a peripheral while scanning for devices.
func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral,advertisementData: [String : Any], rssi RSSI: NSNumber) {
bluefruitPeripheral = peripheral
bluefruitPeripheral.delegate = self
print("Peripheral Discovered: \(peripheral)")
print("Peripheral name: \(peripheral.name)")
print ("Advertisement Data : \(advertisementData)")
centralManager?.stopScan()
}
The implementation of this function performs the following actions:
- Set the
bluefruitPeripheralvariable to the new peripheral found. - Set the peripheral's delegate to self (ViewController)
- Printed the newly discovered peripheral's information in the console.
- Stopped scanning for peripherals.
Next up - actually connect to that peripheral.
Page last edited March 08, 2024
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