读取 BLE 外设特性并检查其值? [英] Reading a BLE Peripheral Characteristic and checking its value?

问题描述

我正在 Xcode 上使用 Swift 编写一个应用程序，该应用程序连接到蓝牙 BLE 外设.我已经建立了与设备的连接，并想从特定特征(特别是服务 UUID FFF0 中的 FFF1)读取一些数据.

I'm writing an app using Swift on Xcode that connects to a bluetooth BLE peripheral. I've established a connection to a the device, and want to read some data from a specific characteristic (specifically FFF1 in service UUID FFF0).

如果我要查找信息的特征是 characteristicx，我可以使用以下代码请求读取特征:

I'm able to request a read of characteristics using the following code if the characteristic that I want to find info for is characteristicx:

peripheral.readValueForCharacteristic(charactericsx)

我想知道的是:如何检查此读取值是否是我要查找的值.我希望能够执行 if 语句来根据该特征的发现值检查我的值.

What I want to know is this: How do I check that this read value is what I'm looking for. I want to be able to do an if statement to check my value against the discovered value for that characteristic.

例如:如果发现的值为 X 则做某事，否则如果发现的值为 Y 则做其他的事情.

Eg: If discovered value is X then do something, else if discovered value is Y then do something else.

这不是我想要做什么的一个很好的解释，但我希望你明白要点.

That's not a very good explanation of what I want to do, but I hope you get the gist.

有人知道怎么做吗?

推荐答案

已针对 Swift3 更新

执行该方法后，外围设备的delegate 将异步接收peripheral(_:didUpdateValueFor:error:) 方法.在该方法中，您可以查询传递的 characteristic 参数的 value.value 将是一个 NSData，您可以从中提取字节.例如

After you execute that method, the delegate of your peripheral is going to asynchronously receive the peripheral(_:didUpdateValueFor:error:) method. In that method you can query the value of the passed characteristic parameter. value will be an NSData which you can pull the bytes out of. E.g.

// MARK: - CBPeripheralDelegate
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
    if let e = error {
        print("ERROR didUpdateValue (e)")
        return
    }
    guard let data = characteristic.value else { return }
    ...
}

value 方法实际上在预期的 Data 周围返回了一个 Optional，所以要使用 let 守卫.

The value method actually returns an Optional around the expected Data, so a let guard is the way to go.

通常，一个特性会有一个简单的值编码在它的最多 20 字节的 Data 负载中.例如.也许这是一个简单的 UInt16 计数器.到

Usually a characteristic will have a simple value encoded in it's up-to-20-byte Data payload. E.g. maybe it's a simple UInt16 counter. To

要在这些 Data 数据和有意义的数字之间进行转换，请查看 往返 Swift 数字类型到/从数据(我在下面包含了我自己的实现).

To convert between these Data glumps and meaningful numbers, have a look at the answer to round trip Swift number types to/from Data (I've included my own implementation of that below).

因此，例如，如果您知道感兴趣的特征是某个旨在作为 UInt16 提取的计数器，我将使用以下内容填写上面的示例:

So for example, if you know that the characteristic of interest is some counter that is a meant to be extracted as a UInt16, I would fill out the above example with something like:

// MARK: - CBPeripheralDelegate
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
    if let e = error {
        print("ERROR didUpdateValue (e)")
        return
    }
    guard let data = characteristic.value else { return }
    print("counter is (UInt16(data:data))")
}



// Data Extensions:
protocol DataConvertible {
    init(data:Data)
    var data:Data { get }
}

extension DataConvertible {
    init(data:Data) {
        guard data.count == MemoryLayout<Self>.size else {
            fatalError("data size ((data.count)) != type size ((MemoryLayout<Self>.size))")
        }
        self = data.withUnsafeBytes { $0.pointee }
    }

    var data:Data {
        var value = self
        return Data(buffer: UnsafeBufferPointer(start: &value, count: 1))
    }
}

extension UInt8:DataConvertible {}
extension UInt16:DataConvertible {}
extension UInt32:DataConvertible {}
extension Int32:DataConvertible {}
extension Int64:DataConvertible {}
extension Double:DataConvertible {}
extension Float:DataConvertible {}

这篇关于读取 BLE 外设特性并检查其值?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！