从Swift中读取蓝牙的特性值

Question

我试图从BT设备读取并转换成字符串读取。

<CBCharacteristic: 0x1700a2e80, UUID = 2A9D, properties = 0x20, value = <02ac08e1 07010a14 0029>, notifying = YES> 

基于例如我在网上找到我做

let u16 = (characteristic.value! as NSData).bytes.bindMemory(to: Int.self, capacity: characteristic.value!.count).pointee 

，但我的U16为空，即使characteristic.value包含

(lldb) dp characteristic.value! as NSData 
<02ac08e1 07010a14 0029> 

任何人都可以点我在正确的方向？

Answer 1

这不是很容易。

Weight Measurement

您可能需要编写这样的事：

let data = Data([0x02,0xac,0x08,0xe1,0x07,0x01,0x0a,0x14,0x00,0x29]) 

struct DataReader { 
    var data: Data 
    var offset: Int = 0 

    mutating func read() -> UInt8 { 
     let result = data[offset] 
     offset += MemoryLayout<UInt8>.size 
     return result 
    } 
    mutating func read() -> UInt16 { 
     let subdata = data.subdata(in: offset..<offset+MemoryLayout<UInt16>.size) 
     let result: UInt16 = subdata.withUnsafeBytes {(bytes: UnsafePointer<UInt16>) in 
      bytes.pointee.littleEndian 
     } 
     offset += MemoryLayout<UInt16>.size 
     return result 
    } 
} 

typealias BLEUserID = UInt8 

struct BLEDateTime { 
    var year: UInt16 
    var month: UInt8 
    var day: UInt8 
    var hours: UInt8 
    var minutes: UInt8 
    var seconds: UInt8 
} 
extension DataReader { 
    mutating func read() -> BLEDateTime { 
     let year: UInt16 = read() 
     let month: UInt8 = read() 
     let day: UInt8 = read() 
     let hours: UInt8 = read() 
     let minutes: UInt8 = read() 
     let seconds: UInt8 = read() 
     return BLEDateTime(year: year, month: month, day: day, hours: hours, minutes: minutes, seconds: seconds) 
    } 
} 
struct WeightMeasurement: CustomStringConvertible { 
    struct Flags: OptionSet { 
     var rawValue: UInt8 
     init(rawValue: UInt8) { 
      self.rawValue = rawValue 
     } 
     static let measurementImperial = Flags(rawValue: 1<<0) 
     static let timeStampPresent = Flags(rawValue: 1<<1) 
     static let userIDPresent = Flags(rawValue: 1<<2) 
     static let bmiAndHeightPresent = Flags(rawValue: 1<<3) 
    } 
    var isMeasuremntImperial: Bool 
    var weight: Decimal 
    var timeStamp: BLEDateTime? 
    var userID: BLEUserID? 
    var bmi: Decimal? 
    var height: Decimal? 

    var description: String { 
     return weight.description 
    } 
} 
extension DataReader { 
    mutating func read() -> WeightMeasurement { 
     let flags = WeightMeasurement.Flags(rawValue: read()) 
     let isMeasuremntImperial = flags.contains(.measurementImperial) 
     let weight: Decimal 
     if isMeasuremntImperial { 
      weight = Decimal(read() as UInt16) * Decimal(string: "0.01")! 
     } else { 
      //SI 
      weight = Decimal(read() as UInt16) * Decimal(string: "0.005")! 
     } 
     var timeStamp: BLEDateTime? 
     if flags.contains(.timeStampPresent) { 
      timeStamp = read() 
     } 
     var userID: BLEUserID? 
     if flags.contains(.userIDPresent) { 
      userID = read() 
     } 
     var bmi: Decimal? 
     var height: Decimal? 
     if flags.contains(.bmiAndHeightPresent) { 
      bmi = Decimal(read() as UInt16) * Decimal(string: "0.1")! 
      if isMeasuremntImperial { 
       height = Decimal(read() as UInt16) * Decimal(string: "0.1")! 
      } else { 
       //SI 
       height = Decimal(read() as UInt16) * Decimal(string: "0.001")! 
      } 
     } 
     return WeightMeasurement(isMeasuremntImperial: isMeasuremntImperial, weight: weight, timeStamp: timeStamp, userID: userID, bmi: bmi, height: height) 
    } 
} 

var reader = DataReader(data: data, offset: 0) 
let weightMeasurement: WeightMeasurement = reader.read() 
print(weightMeasurement) //->11.1 
print(weightMeasurement.timeStamp!) //->BLEDateTime(year: 2017, month: 1, day: 10, hours: 20, minutes: 0, seconds: 41) 

（对不起，没有充分测试，你可能需要做一些修改。）