iPad连接RPP02热敏打印机打印失败问题求助

我需要在iPad设备上向RPP02型号（VRTEC热敏打印机）打印内容。该打印机在我的安卓项目中可正常使用，且我了解到它支持蓝牙4.0。我创建了一个包含扫描设备及打印按钮的简单项目，但始终无法成功打印，怀疑是CBCharacteristic使用有误。以下是项目代码及调试信息：

import UIKit
import CoreBluetooth

fileprivate func < <T : Comparable>(lhs: T?, rhs: T?) -> Bool {
  switch (lhs, rhs) {
  case let (l?, r?):
    return l < r
  case (nil, _?):
    return true
  default:
    return false
  }
}

extension String {
    struct GBEncoding {
        public static let GB_18030_2000 = String.Encoding(rawValue: CFStringConvertEncodingToNSStringEncoding(CFStringEncoding(CFStringEncodings.GB_18030_2000.rawValue)))
    }
}


class BluetoothConnect: UIViewController, CBCentralManagerDelegate,  CBPeripheralDelegate, UITableViewDelegate, UITableViewDataSource {
    
    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var buttonTestPrint: UIButton!
    
    @IBAction func onClickBarItemClose(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true, completion: nil)
    }
    
    @IBAction func onClickButtonTestPrint(_ sender: UIButton) {
        dataToSend = "TEST PRINT GOOOOO".data(using: String.Encoding.utf8)
        sendDataIndex = 0
        sendData()
        
        let line = "FORMFEED"
        peripheral?.writeValue(line.data(using: .utf8)!, for: service.characteristics![3], type: .withResponse)
        peripheral?.writeValue(line.data(using: String.GBEncoding.GB_18030_2000)!, for: service.characteristics![3], type: .withResponse)
        peripheral?.writeValue(Data(Array(line.utf8)), for: service.characteristics![3], type: .withResponse)

    }
    
    var centralManager: CBCentralManager!
    var peripheral: CBPeripheral!
    var service: CBService!
    var characteristic: CBCharacteristic!

    var dataPeripheral: [CBPeripheral] = [CBPeripheral]()
    var dataPrinterDevice: [Any] = [Any]()

    var bluetoothAvailable = false

    override func viewDidLoad() {
        super.viewDidLoad()

        self.centralManager = CBCentralManager(delegate: self, queue: .main)
        
        self.tableView.delegate = self
        self.tableView.dataSource = self
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        self.centralManager.stopScan()
    }
    

    // MARK: - Table View Delegate
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.dataPrinterDevice.count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "DevicePrinterCell", for: indexPath)
        return cell
    }
    
//    // MARK: - Central Manager Delegate
    func centralManager(_ central: CBCentralManager, didDisconnectPeripheral peripheral: CBPeripheral, error: Error?) {
        print("disconnect \(String(describing: peripheral.name))")
    }

    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
        if (!self.dataPeripheral.contains(peripheral)) {
            if (String(describing: peripheral.name) != "nil" || peripheral.name != nil) {
                if let power = advertisementData[CBAdvertisementDataTxPowerLevelKey] as? Double {
                    guard let uniqueIDs = advertisementData[CBAdvertisementDataServiceUUIDsKey] as? [CBUUID], let uniqueID = uniqueIDs.last  else { return }

                    var objPeripheral: [AnyHashable: Any] = [AnyHashable: Any]()
                    objPeripheral.updateValue(power, forKey: "power")
                    objPeripheral.updateValue(peripheral.name!, forKey: "name")
                    objPeripheral.updateValue(uniqueID.uuidString, forKey: "uuid")

                    self.dataPeripheral.append(peripheral)
                    self.dataPrinterDevice.append(objPeripheral)
                    self.tableView.reloadData()

                    print("Name : ", peripheral.name!)
                    print("UUID : ", uniqueID.uuidString)
                    
                    self.centralManager?.connect(peripheral, options: nil)
                }
            }
        }

    }

    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        print("Checking state")
        switch (central.state) {
            case .poweredOn:
                print("CoreBluetooth BLE hardware is powered on and ready")
                self.bluetoothAvailable = true;

            @unknown default:
                print("Central State None Of The Above")
        }


        if bluetoothAvailable == true {
            self.discoverDevices()
        }
    }

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


    // MARK: - Peripheral Delegate
    func peripheral(_ peripheral: CBPeripheral, didWriteValueFor characteristic: CBCharacteristic, error: Error?) {
        print("sent \(characteristic)")
    }

    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        
        for service in peripheral.services! {
            print("Service \(service)\n")
            print("Discovering Characteristics for Service : \(service.uuid)")
            print(service.characteristics as Any)

            self.service = service
            self.peripheral.discoverCharacteristics(nil, for: service )
        }
    } 
    
    func discoverDevices() {
        print("Discovering devices")
        self.centralManager.scanForPeripherals(withServices: nil)
    }
}

调试信息 #

点击打印按钮获取的peripheral信息：

<CBPeripheral: 0x28260dfe0, identifier = 2B2A97C8-F3A3-AD56-19C1-0CA2E011712D, name = BlueTooth Printer, mtu = 185, state = connected>

服务对应的characteristic信息：

<__NSArrayI 0x281800270>(
<CBCharacteristic: 0x28335f300, UUID = Serial Number String, properties = 0x2, value = (null), notifying = NO>,

<CBCharacteristic: 0x28335d860, UUID = Software Revision String, properties = 0x2, value = (null), notifying = NO>,

<CBCharacteristic: 0x28335d980, UUID = Hardware Revision String, properties = 0x2, value = (null), notifying = NO>,

<CBCharacteristic: 0x28335c480, UUID = Manufacturer Name String, properties = 0x2, value = (null), notifying = NO>
)

内容的提问来源于stack exchange，提问作者MrX