5 replies to this topic

[Stefan]

Second sample, a bit more complex, using events:

Imports Microsoft.SPOT
Imports Microsoft.SPOT.Hardware
Imports SecretLabs.NETMF.Hardware
Imports SecretLabs.NETMF.Hardware.Netduino

Module Module1

    Public led As OutputPort = New OutputPort(Pins.ONBOARD_LED, False)

    Sub Main()
        Dim button As InterruptPort = New InterruptPort(Pins.ONBOARD_SW1, False, Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeBoth)
        AddHandler button.OnInterrupt, AddressOf ButtonChange
        button.EnableInterrupt()

        Thread.Sleep(Timeout.Infinite)

    End Sub

    Sub ButtonChange(ByVal data1 As UInteger, ByVal data2 As UInteger, ByVal time As Date)
        If data2 = 0 Then led.Write(False) Else led.Write(True)
    End Sub

End Module

When pushing the onboard button, the onboard led is emitting.

Attached Files

•  VB.NETMF Events.zip   2.44K   30 downloads

[Joe Griffith]

For what it is worth I tried declaring the button WithEvents and putting a Handles clause at the end of the ButtonChange method. This would be my prefered syntax and it is accepted by the IDE but, alas, it doesn't work.

[Stefan]

True, as far as I know that's still in progress. I've reported it as a bug which was confirmed.

[rhamer]

Has anybody come accross a problem where the events stop firing?

I have an application that has an event tied to an input and after a while it stops firing.

The way the event handler is written is exactly as shown in the example above, and it works properly for the first 10 or so pin level changes, then suddenly just stops firing.

I have tried the sample program above, and the problem does not happen, so it is difficult for me to identify exactly what is the problem.

Stripping down the application is not an easy task as it is quite a big complex application, and the latest thing added was the use of the events to monitor one of the digital inputs, which is actually driven by the interrupt pin of a MCP23017 port expander.

When this problem occurs, the rest of the application keeps running fine, the event handler just never gets called.

If I run a poll timer in the background that manually calles the same event handler after a few minutes, then all the code inside it runs correctly.

I have also used a logic analyser to monitor the state of the pin, and it is actually being pulled low by the MCP23017 as it should.

Regards

Rohan

[Chris Walker]

Hi Rohan,

Is it possible that something is going out of scope and getting garbage collected? Also, are you calling the event from a background thread by any chance (which could itself have crashed)?

I haven't seen event handlers just stop working in the background, so I'm really interested in finding out what's going on.

Chris

[rhamer]

Yes you were spot on, the event handler definition was in a thread that was going out of scope.

It seems to be working ok now.

Thanks for your help.

Regards

Rohan