iOS Connect and read major value


Example

  • I'm in a controlled room with a single minew beacon that use IBEACON protocol.
  • BLEController needs to extend CBPeripheralDelegate
  • I'll use the first BLE to connect after the search has stop.
  • Modify the method StopSearchBLE()
class BLEController: CBCentralManagerDelegate, CBPeripheralDelegate{
//...
    func StopSearchMiniewBeacon() {
        let when = DispatchTime.now() + 5 // change 2 to desired number of seconds
        DispatchQueue.main.asyncAfter(deadline: when) {
            self.cb_manager.stopScan()
            self.cb_manager.connect(bles.first)
        }
    }
/...
}
  • In the documention of your BLE device, you should look for the SERVICE UUID and MAJOR UUID CHARACTERISTIC
var service_uuid =  CBUUID(string: "0000fff0-0000-1000-8000-00805f9b34fb")
var major_uuid =  CBUUID(string: "0000fff2-0000-1000-8000-00805f9b34fb")
func centralManager(_ central: CBCentralManager, didConnect peripheral:             
CBPeripheral) {
    peripheral.delegate = self
    peripheral.discoverServices([service_uuid])
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
    print("Service: \(service)\n error: \(error)")
    peripheral.discoverCharacteristics([major_uuid], for: (peripheral.services?[0])!)
}
  • Create a variable 'service_uuid' and 'major_uuid' like code above. '-0000-1000-8000-00805f9b34fb' is part of the standard. 'fff0' is my SERVICE UUID, 'fff2' is my MAJOR UUID characteristic and '0000' are required to fill the 4 bytes uuid 1º block.
  • discoverCharacteristics([major_uuid], for: (peripheral.services?[0])!) will get major characteristic from my device gatt server and it will have NIL as value for now.
  • (peripheral.services?[0])! - 0 beacuse will return a single value once I did peripheral.discoverServices([service_uuid])
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
    for characteristic in service.characteristics! {
        print("Characteristic: \(characteristic)\n error: \(error)")
        if(characteristic.uuid.uuidString == "FFF2"){
            peripheral.readValue(for: characteristic)
        }
    }
}

func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
    print("Characteristic read: \(characteristic)\n error: \(error)")
    let major = UInt16.init(bigEndian: UInt16(data: characteristic.value!)!)
    print("major: \(major)")
}
  • Characteristic value will only be readable after call peripheral.readValue(for: characteristic)
  • readValue will result in func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) with value in Data type.