滚动平均值，vb.net

Question

我有一个传感器（实际上是 Quartzonix 压力传感器）通过串口输出数据，大约每秒 3 次。我想设置一些代码，根据 x 样本量给我一个平均读数。

输出看起来像这样：

01+   1.502347091823e01
01+   1.501987234092e01
01+   1.50234524524e01
01+   1.502123412341e01
01+   1.502236234523e01
01+   1.50198345e01
01+   1.502346234523e01

.. 并将一直持续下去，直到 com 端口关闭或传感器收到另一个命令。

这是我目前拥有的代码，该代码向我展示了传感器实际输出的内容：

Private Sub btnStart_Click(sender As Object, e As EventArgs) Handles btnStart.Click
    Dim a As String
    a = "MC" & Chr(13)
    MyComPort.WriteLine(a)

    Do
        Dim Incoming As String = MyComPort.ReadLine()
        Dim incomingtext As String = Incoming.Remove(0, 3)

        If Incoming Is Nothing Then
            Exit Do
        Else
            txtRawData.Text = Incoming
            boxPSIA.Text = Format(Val(incomingtext), "##0.000")

        End If
        Application.DoEvents()
    Loop

End Sub

“$01MC”是传感器开始吐出数据所需的命令。当我点击开始按钮时，我发生了一些奇怪的超时事件，但那是另一个节目（可能需要调整 .readtimeout，不确定）。

我有一个文本框 txtReadingsToAvg，用于输入平均读数的数量。我只是没有思考如何真正让它计算平均值（比如，单击按钮然后随地吐痰它输出到一个消息框，甚至另一个文本框）。

Answer 1

不确定您的代码是如何工作的。你说你得到值 @ 大约 3 赫兹？那么直线上升 Do...Loop 就太快了。当串行端口接收到数据时会引发一个事件。好好利用它。

您可能需要稍微更改一下以满足您的需要

' WithEvents allows events to be handled with "Handles" keyword
Private WithEvents myComPort As SerialPort
Private dataQueue As Queue(Of Double)
Private numReadingsToAvg As Integer = 0

Private Sub btnStart_Click(sender As Object, e As EventArgs) Handles btnStart.Click
    ' make a new queue here to initialize or clear an old queue
    dataQueue = New Queue(Of Double)()
    ' read the num avgs text box. you may want to change on the fly also
    numReadingsToAvg = Integer.Parse(Me.txtReadingsToAvg.Text)
    myComPort.WriteLine("MC" & Chr(13))
End Sub

Private Sub myComPort_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) Handles myComPort.DataReceived
    Dim incomingLine As String = myComPort.ReadLine()
    ' DataReceived event happens on its own thread, not the UI
    ' must invoke call back to UI to change properties of controls
    txtRawData.Invoke(Sub() txtRawData.Text = incomingLine)
    Dim incomingValue As String = incomingLine.Remove(0, 3).Trim()
    If Not String.IsNullOrWhiteSpace(incomingValue) Then
        Exit Sub
    Else
        Dim measurement As Double = Double.Parse(incomingValue)
        boxPSIA.Invoke(Sub() boxPSIA.Text = Format(measurement, "##0.000"))
        dataQueue.Enqueue(measurement)
        ' if there are too many items, remove the last one
        If dataQueue.Count > numReadingsToAvg Then
            dataQueue.Dequeue()
        End If
        Dim average As Double = dataQueue.Average()
        ' you need to add this textbox
        anotherTextBox.Invoke(Sub() anotherTextBox.Text = Format(average, "##0.000"))
    End If
End Sub

顺便说一句，Application.DoEvents() should rarely (never) be used, as there's always a better way to remedy whatever problem you are bandaging with DoEvents。您的原始示例在 UI 上因永无止境的循环运行ning 阻塞了 UI 线程。如果你需要运行这样的循环，它应该几乎总是运行在与 UI 线程不同的线程上。在我的例子中，没有环路，时间由端口自己决定。无需在 UI 线程上发生任何此类情况。

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