hmi_enable_input_clock Property

In This Topic

Description

Controls if HMI input signals are transmitted to JavaScript in real-time or latched.

Property type

Read-write property

Syntax

Visual Basic
Public Property hmi_enable_input_clock As Boolean

Remarks

With WebKitX you can create HMI Dash Boards by forwarding sensor data to HTML and JavaScript for rendering. The input signals are latched and the clock frequency is controlled by Settings.hmi_input_clock_frequency_hz which defaults to 2Hz. This means that input signal values are buffered by WebKitX and are flushed to HTML/JavaScript every 500 milliseconds. If no input signals are registered since last flush then no emission takes place. You can disable the input latch and pass the input signal values at real-time by setting the Settings.hmi_enable_input_clock to False.

Example

Example (Visual Basic)

Option Explicit

Private Sub Form_Resize()
    On Error Resume Next
    WebKitX1.Move 0, 0, ScaleWidth, ScaleHeight
    Err.Clear
End Sub

Private Sub Form_Load()
    
    ' Load Human Machine Interface markup
    WebKitX1.HMI_URL = "file:///" + App.Path + "/index.html"
    
End Sub

Private Sub WebKitX1_OnCreate(ByVal Settings As WebKitXCEF3Lib.ISettings, CommandLineSwitches As String)
            
    ' Set WebKitX HMI values to flush/refresh at rate 1Hz (every 1sec).
    Settings.hmi_enable_input_clock = True
    Settings.hmi_input_clock_frequency_hz = 1
    
End Sub

Private Sub WebKitX1_OnPageComplete(ByVal url As String)
               
    ' We use a timer at 60Hz to simulate high-frequency sensors.
    Timer1.Interval = (1000 / 60)
    Timer1.Enabled = True
    
End Sub

Private Sub Timer1_Timer()
    
    ' We read values from "sensors" and pass them to six (6) different HMI I/O channels.
    ' We read sensor values 60 times per second (every ~16ms). WebKitX uses input latches
    ' to retain input values and flush them to HTML at a rate of 1Hz (every 1sec).
    
    WebKitX1.HMI_VALUE_001 = Rnd * 1560
    WebKitX1.HMI_VALUE_002 = Rnd * 1560
    WebKitX1.HMI_VALUE_003 = Rnd * 1560
    WebKitX1.HMI_VALUE_004 = Rnd * 1560
    WebKitX1.HMI_VALUE_005 = Rnd * 1560
    WebKitX1.HMI_VALUE_006 = Rnd * 1560
            
End Sub

Private Sub WebKitX1_OnHMIControlSignal(ByVal Index As Long, ByVal Data As String)

    Debug.Print Format(Time, "HH:MM:SS") & " > HMI_VALUE_" & Format(Index, "000") & " = " & Data

End Sub

Guides

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