【iOS】【Core bluetooth】8バイトのデータをBLEデバイスにwriteしたい

前提・実現したいこと

BLEデバイスにiPhoneからデータを送信するアプリを作っています。ペアリングはできていますが、データ送信がうまくいっていません。データの記述方法と、Charadteristic UUIDの記述方法をご教授いただきたいです。

発生している問題・エラーメッセージ

エラー等は発生していませんが、データ送信ができていません。
下記のソースコードの、
writeValue(data, for: writeChar, type: .withoutResponse)
の引数が正しくないと思われます。
writeChar にUUIDを持たせるのは
self.writeChar = CBMutableCharacteristic(type: characteristicUUID, properties: properties, value: nil, permissions: permissions)
では不可能なのでしょうか？

該当のソースコード

Swift
1import UIKit
2import CoreBluetooth;
3
4class ViewController: UIViewController,CBCentralManagerDelegate, CBPeripheralDelegate {
5    
6    var serviceUUID : CBUUID!
7    var characteristicUUID : CBUUID!
8    
9    var manager : CBCentralManager!
10    var peripheral : CBPeripheral!
11    var characteristic : CBCharacteristic!
12    var writeChar : CBMutableCharacteristic!
13    
14    let properties = (CBCharacteristicProperties.write)
15    let permissions = (CBAttributePermissions.writeable)
16    
17    
18    @IBOutlet var ConnectButton: UIButton!
19    @IBOutlet var DisconnectButton: UIButton!
20    @IBOutlet var OnButton: UIButton!
21    @IBOutlet var OffButton: UIButton!
22    
23    override func viewDidLoad() {
24        super.viewDidLoad()
25        self.serviceUUID = CBUUID(string: Constants.SERVICE_UUID)
26        self.characteristicUUID = CBUUID(string: Constants.CHARACTERISTIC_UUID)
27        self.manager = CBCentralManager(delegate : self, queue : nil)
28        self.ConnectButton.isEnabled = true
29        self.DisconnectButton.isEnabled = true
30        self.writeChar = CBMutableCharacteristic(type: characteristicUUID, properties: properties, value: nil, permissions: permissions)
31        
32        
33    }
34    
35    override func didReceiveMemoryWarning() {
36        super.didReceiveMemoryWarning()
37        // Dispose of any resources that can be recreated.
38    }
39    @IBAction func ConnectClicked(_ sender: Any) {
40        self.manager.scanForPeripherals(withServices: [self.serviceUUID], options: nil)
41    }
42    @IBAction func DisconnectClicked(_ sender: Any) {
43        self.manager.cancelPeripheralConnection(peripheral)
44    }
45    
46    @IBAction func OnClicked(_ sender: Any) {
47        let ondata: [UInt8] = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01];
48        let data = Data(ondata)
49        peripheral.writeValue(data, for: writeChar, type: .withoutResponse)
50        
51    }
52    
53    @IBAction func OffClicked(_ sender: Any) {
54        let offdata: [UInt8] = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
55        let data = Data(offdata)
56        peripheral.writeValue(data, for: writeChar, type: .withoutResponse)
57        
58    }
59    
60
61    func centralManagerDidUpdateState(_ central: CBCentralManager) {
62    }
63    
64    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
65        
66        self.peripheral = peripheral
67        self.peripheral.delegate = self
68        self.manager.connect(peripheral, options: nil)
69        self.manager.stopScan()
70    }
71    
72    func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
73        self.peripheral.discoverServices([self.serviceUUID])
74    }
75
76    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
77        if (error != nil) {
78            return
79        }
80        let services : [CBService]? = peripheral.services
81        for service in services! {
82            if service.uuid.isEqual(self.serviceUUID) {
83                self.peripheral.discoverCharacteristics(nil, for:service)
84            }
85        }
86    }
87    
88    func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
89        if error != nil {
90            return
91        }
92        let characteristics : [CBCharacteristic]? = service.characteristics
93        for c in characteristics! {
94            if c.uuid.isEqual(self.characteristicUUID) {
95                self.peripheral.readValue(for: c)
96            }
97        }
98    }
99
100}
101