如何使用 BLE OBDII 外设

Question

我正在尝试创建一个将从 OBDII 蓝牙 4 (LE) 设备读取的 iOS 应用程序。我购买了 Vgate icar3 蓝牙（4.0）elm327 OBDII。我把它插到我的车里，发现 IOS-VLink 外围设备宣传了一些服务。然后我可以获得这些服务的特征。这些是我找到的服务：

<CBService: 0x1780729c0, isPrimary = YES, UUID = Battery>
<CBService: 0x178072a80, isPrimary = YES, UUID = 1803>
<CBService: 0x178072ac0, isPrimary = YES, UUID = 1802>
<CBService: 0x178072b00, isPrimary = YES, UUID = 1811>
<CBService: 0x178072b40, isPrimary = YES, UUID = 1804>
<CBService: 0x178072b80, isPrimary = YES, UUID = 18F0>
<CBService: 0x178072bc0, isPrimary = YES, UUID = Device Information>
<CBService: 0x178072c00, isPrimary = YES, UUID = E7810A71-73AE-499D-8C15-FAA9AEF0C3F2>

但我不知道1803、1802、1811、1804和18F0服务是什么，也不知道如何使用它们。这是我的简单程序，用于找出正在宣传的内容。

class ViewController: UIViewController, CBCentralManagerDelegate, CBPeripheralDelegate {

var centralManager = CBCentralManager()
var peripherals = [CBPeripheral]()
@IBOutlet weak var outputTextView: UITextView!

override func viewDidLoad() {
    super.viewDidLoad()
    centralManager.delegate = self
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
    print("connected to \(peripheral.name ?? "unnamed")")
    peripheral.delegate = self
    peripheral.discoverServices(nil)
}

func centralManagerDidUpdateState(_ central: CBCentralManager) {
    if central.state == .poweredOn {
        central.scanForPeripherals(withServices: nil, options: nil)
    }
}

func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
    if peripheral.name == "IOS-Vlink" {
        peripherals.append(peripheral)
        print(peripheral.name ?? "peripheral has no name")
        print(peripheral.description)
        central.connect(peripheral, options: nil)
        central.stopScan()
    }

}

func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
    guard let services = peripheral.services else {
        return
    }
    for service in services {
        print(service.description)
        peripheral.discoverCharacteristics(nil, for: service)
    }
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
    guard let chars = service.characteristics else {
        return
    }
    for char in chars {
        print(char.description)
    }
}
}

Answer 1

我想到了。“E7810A71-73AE-499D-8C15-FAA9AEF0C3F2”服务的特征是uuid为“BEF8D6C9-9C21-4C9E-B632-BD58C1009F9F”。如果您向该特征写入 AT 命令，则它会调用peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?)并在 value 属性中获取结果。这是发送简单 ATZ 命令的代码。此时它只是使用正确的 OBDII ELM327 命令。

class ViewController: UIViewController, CBCentralManagerDelegate, CBPeripheralDelegate {

var centralManager = CBCentralManager()
var peripherals = [CBPeripheral]()
@IBOutlet weak var outputTextView: UITextView!

override func viewDidLoad() {
    super.viewDidLoad()
    centralManager.delegate = self
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
    print("connected to \(peripheral.name ?? "unnamed")")
    peripheral.delegate = self
    peripheral.discoverServices([CBUUID(string:"E7810A71-73AE-499D-8C15-FAA9AEF0C3F2")])
}

func centralManagerDidUpdateState(_ central: CBCentralManager) {
    if central.state == .poweredOn {
        central.scanForPeripherals(withServices: nil, options: nil)
    }
}

func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
    if peripheral.name == "IOS-Vlink" {
        peripherals.append(peripheral)
        print(peripheral.name ?? "peripheral has no name")
        print(peripheral.description)
        central.connect(peripheral, options: nil)
        central.stopScan()
    }

}

func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
    guard let services = peripheral.services else {
        return
    }
    for service in services {
        peripheral.discoverCharacteristics([CBUUID(string:"BEF8D6C9-9C21-4C9E-B632-BD58C1009F9F")], for: service)
    }
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
    guard let chars = service.characteristics else {
        return
    }
    guard chars.count > 0 else {
        return
    }
    let char = chars[0]
    peripheral.setNotifyValue(true, for: char)
    peripheral.discoverDescriptors(for: char)

    print (char.properties)
    peripheral.writeValue("ATZ\r\n".data(using: .utf8)!, for: char, type: CBCharacteristicWriteType.withResponse)

    peripheral.readValue(for: char)
    if let value = char.value {
        print(String(data:value, encoding:.utf8) ?? "bad utf8 data")
    }
}

func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
    if let value = characteristic.value {
        print(String(data:value, encoding:.utf8)!)
    }
}
func peripheral(_ peripheral: CBPeripheral, didDiscoverDescriptorsFor characteristic: CBCharacteristic, error: Error?) {
    print(characteristic.descriptors ?? "bad didDiscoverDescriptorsFor")
}
func peripheral(_ peripheral: CBPeripheral, didWriteValueFor characteristic: CBCharacteristic, error: Error?) {
    if let error = error {
        print(error)
    }
    print("wrote to \(characteristic)")
    if let value = characteristic.value {
        print(String(data:value, encoding:.utf8)!)
    }
}
}