Isuru Isuru - 1 year ago 112
iOS Question

Receive string data via Bluetooth

I'm creating a simple BLE app that communicates with a single peripheral. The phone acts as the central. I have an iPad which I'm using as the peripheral for testing. It has the app LightBlue installed to simulate a peripheral. The peripheral is supposed to send a string of data in this format.


TEM:25.11 | HUM:70 | PM10:43 | PM25:32


So I created a blank virtual peripheral in LightBlue with one service.

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enter image description here

Below is my code for Bluetooth connectivity handling.

import UIKit
import CoreBluetooth

class ViewController: UIViewController {

fileprivate let serviceUUID = CBUUID(string: "19B10010-E8F2-537E-4F6C-D104768A1214")
fileprivate let characteristicUUID = CBUUID(string: "19B10011-E8F2-537E-4F6C-D104768A1214")

fileprivate var manager: CBCentralManager!
fileprivate var peripheral: CBPeripheral!
fileprivate var characteristic: CBCharacteristic!

override func viewDidLoad() {
super.viewDidLoad()
manager = CBCentralManager(delegate: self, queue: nil)
}

override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
stopScan()
}

fileprivate func startScan() {
manager.scanForPeripherals(withServices: [serviceUUID], options: nil)
}

fileprivate func stopScan() {
manager.stopScan()
}

fileprivate func disconnectFromDevice() {
guard let peripheral = peripheral else { return }
manager.cancelPeripheralConnection(peripheral)
}

fileprivate func restoreCentralManager() {
manager.delegate = self
}

}

// MARK: - CBCentralManagerDelegate
extension ViewController: CBCentralManagerDelegate {
func centralManagerDidUpdateState(_ central: CBCentralManager) {
switch central.state {
case .unsupported:
print("Unsupported")
case .unauthorized:
print("Unauthorized")
case .poweredOn:
print("Powered On")
startScan()
case .resetting:
print("Resetting")
case .poweredOff:
print("Powered Off")
case .unknown:
print("Unknown")
}
}

func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
print("Discovered \(String(describing: peripheral.name)) at \(RSSI)")

if peripheral.name == nil || peripheral.name == "" {
return
}

if self.peripheral == nil || self.peripheral.state == .disconnected {
stopScan()

self.peripheral = peripheral
central.connect(peripheral, options: nil)
}
}

func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
peripheral.delegate = self
peripheral.discoverServices([serviceUUID])
}

func centralManager(_ central: CBCentralManager, didDisconnectPeripheral peripheral: CBPeripheral, error: Error?) {

self.peripheral = nil
central.scanForPeripherals(withServices: nil, options: nil)
}

func centralManager(_ central: CBCentralManager, didFailToConnect peripheral: CBPeripheral, error: Error?) {
self.peripheral = nil
}

func centralManager(_ central: CBCentralManager, willRestoreState dict: [String : Any]) {
}
}

// MARK: - CBPeripheralDelegate
extension ViewController: CBPeripheralDelegate {
func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
guard let services = peripheral.services else { return }
print("No. of services: \(services.count)")

for service in services {
print(service.uuid)
if service.uuid == serviceUUID {
peripheral.discoverCharacteristics(nil, for: service)
}
}
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
guard let characteristics = service.characteristics else { return }

for characteristic in characteristics {
print("characteristic: \(characteristic.uuid)")
if characteristic.uuid == characteristicUUID {
self.characteristic = characteristic
peripheral.setNotifyValue(true, for: characteristic)
peripheral.readValue(for: characteristic)
}
}
}

func peripheral(_ peripheral: CBPeripheral, didWriteValueFor characteristic: CBCharacteristic, error: Error?) {
print(error)
}

func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
if characteristic.uuid == characteristicUUID {
print("Got reply from: \(characteristic.uuid)")
print(characteristic.value)
if let data = characteristic.value, let string = String(data: data, encoding: String.Encoding.utf8) {
print(string)
} else {
print("No response!")
}
}
}

}


The discovering and connecting part works just fine. The problem is I don't receive that data string from the peripheral.

The method
peripheral(_:didUpdateValueFor:error:)
does get fired. I get the Got reply from: 19B10011-E8F2-537E-4F6C-D104768A1214 output in the console. However when I tried to see if there's any data by printing out the
characteristic.value
, it returns
nil
.

Not sure if it's something wrong with my code. Or I've configured the peripheral on LightBlue wrong. Does LightBlue send out data automatically? I don't see any Send button or anything anywhere either.

I uploaded a demo project here as well.

Answer Source

Your LightBlue configuration showing that you can only write value on that particular characteristic You have to make this read also

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