Is there a VISA driver for vb.net yet?

[saikey]

I actually haven't tried to use the events yet. But looking in the help index for callback function showed :

using System;
using System.Runtime.InteropServices;

public delegate bool CallBack(int hwnd, int lParam);

public class EnumReportApp {

[DllImport("user32")]
public static extern int EnumWindows(CallBack x, int y);

public static void Main()
{
CallBack myCallBack = new CallBack(EnumReportApp.Report);
EnumWindows(myCallBack, 0);
}

public static bool Report(int hwnd, int lParam) {
Console.Write("Window handle is ");
Console.WriteLine(hwnd);
return true;
}
}

Looks pretty straight forward. Just declare a new instance of viEventHandler passing your function to th
e constructor. Then pass the instance of viEventHandler to viInstallHandler.

Also for the viStatusDesc you should have been able to declare it this way:

[DllImport("visa32.dll")] public static extern
System.Int32 viStatusDesc (System.UInt32 vi, System.UInt32 status,[MarshalAs(UnmanagedType.VBByRefStr)] ref System.String desc);

[Electroman]

Thank you so much for this example. I will try it out immidiately. I tried looking through the help for an example like this but to no avail. I should have used "callback" in the search criteria as you did. This looks pretty straight forward now that I see it in black and white but as I tried doing it on my own, for some reason it didn't seem that intuitive. Thanks again. Yes the viStatusDesc works that way as well, I just preffer the byte array method because that is what I am used to.

[Electroman]

saikey,
I just can't seem to get the viEnableEvent function to work correctly. It returns a VI_ERROR_SYTEM_ERROR. I have a feeling that it has to do with the original function requiring a void* data type. Do you have any ideas.

Thanks again for your help.

[saikey]

Change the return type for the delegate to System.Int32.
Make sure that your event handler is declared static.
Should work fine now.

uint defRM = 0, vi = 0;
int stat = 0;
VISA.viOpenDefaultRM(ref defRM);
VISA.viOpen(defRM, "GPIB0::23::INSTR", 0, 2000, ref vi);
viEventHandler SRQ = new viEventHandler(Form1.fSRQ);
VISA.viInstallHandler(vi, VISA.VI_EVENT_SERVICE_REQ, SRQ, 0);
stat = VISA.viEnableEvent(vi, VISA.VI_EVENT_SERVICE_REQ, VISA.VI_HNDLR, 0);

switch(stat) {
case VISA.VI_ERROR_INV_OBJECT:
listBox1.Items.Add("INV_OBJECT");
break;
case VISA.VI_ERROR_INV_EVENT:
listBox1.Items.Add("INV_EVENT");
break;
case VISA.VI_ERROR_INV_MECH:
listBox1.Items.Add("
INV_MECH");
break;
case VISA.VI_ERROR_INV_CONTEXT:
listBox1.Items.Add("INV_CONTEXT");
break;
case VISA.VI_ERROR_HNDLR_NINSTALLED:
listBox1.Items.Add("HNDLR_NINSTALLED");
break;
case VISA.VI_ERROR_NSUP_MECH:
listBox1.Items.Add("NSUP_MECH");
break;
case VISA.VI_SUCCESS:
listBox1.Items.Add("SUCCESS");
break;
default:
listBox1.Items.Add("UNK");
break;
}

VISA.viClose(vi);
VISA.viClose(defRM);
}

public static System.Int32 fSRQ(System.UInt32 vi, System.UInt32 eventType, System.UInt32 viEvent, System.UInt32 userHandle) {
return VISA.VI_SUCCESS;
}

this returns VI_SUCCESS on viEnableEvent.
don't know if it really gets the event or not.

Thanks for your help with the debugging.

[Mark_BlueMax]

Excellent postings here saikey

Exactly the jump start I was looking for.

[expediter]

I 2nd that!!

Thanks,
Ken M/A-COM

[mbaker]

Thanks for files. It was big help