Hi Ken,

>   Dim bytUART_Byte As Byte
>
>   bytUART_Byte = CType(AxMSComm1.Input(), Byte())(0)

VB.NET is now a 'true' object orientated language like java or C#. 

Lets break it down..

AxMSComm1.Input() returns an Object which is actually a System.Array object
which is actually an array of Bytes.. If you think of it in terms of say
pointers Object -> System.Array -> Byte() -- this is conceptual not literal
but it should help think 'object's

So if we think about what the underlying .NET Virtual Machine is doing by
replacing the AxMSComm1.Input() we can see

Eval 1:  bytUART_Byte = CType( Object -> System.Array -> Byte() , Byte())(0)

Ok. So now what Ctype( object, Type) does it to convert or cast, or really
in this case traverse the pointer heirachy looking for the matching Byte()
array that we are interested in so it basically trims off the
Object->System.Array   and just returns the Byte Array Byte()

Eval 2: bytUART_Byte = Byte()(0)

So now you can more easily see what the (0) is.. It is the zeroth index into
the Byte Array 


This is equivalent to this code

   Dim InputObject as Object
   Dim InputByteArray() As Byte
   Dim bytUART_Byte as Byte

	InputObject    = AxMSComm1.Input()
	InputByteArray = CType(AxMSComm1.Input(), Byte())
	bytUART	   = InputByteArray(0)

So to understand physically what is happening..

Say you send 'HI' on the serial connection you can imagine the Serial
InputBuffer having

MSComm.InputBuffer = {'H','I'}

Now because you are settings are to read only a single byte at a time,
executing AxMSComm1.Input() returns only a single element array, and leaves
the other byte in the InputBuffer for next time

--
InputObject    = AxMSComm1.Input()

MSComm.InputBuffer = {'I'}
InputObject        = Object->System.Array->ByteArray->{'H'}

--

So now you only have an Object reference but you want to get access to the
ByteArray so this is where you you CType

InputByteArray = CType(AxMSComm1.Input(), Byte())
Which gives
InputByteArray = Byte(){'H'}

--

So Finally you want to get the first ( and only ) element from this array
and keep it as bytUART_Byte

byteUART	   = InputByteArray(0)

Which gives

byteUART = 72 ' 'H' = 72


Hope this helps :-)

Cheers,

James Caska
www.muvium.com
uVM - 'Java Bred for Embedded'



-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Ken Pergola
Sent: Friday, October 01, 2004 9:40 PM
To: Microcontroller discussion list - Public.
Subject: RE: [EE] Serial port control under VB.NET 2002/2003



James Caska wrote:

> If you have Strict Mode on then you will need to explicitly cast the 
> Input to a Byte Array. I think someone said something like this
earlier also.
>
>
>   Dim bytUART_Byte As Byte
>
>   bytUART_Byte = CType(AxMSComm1.Input(), Byte())(0)


Hi James,

Thanks kindly James -- yes that's it. I don't quite understand it yet, but
I'll have to research the CType and read up on it. The '(0)' suffix gives me
a buzz cut -- not sure what that is doing. Any chance you can point me to a
link that describes that?

In any event, the simple project showing how to use the MSCOMM control in
BINARY mode under VB.NET works. Thanks to all who helped me out to convert
the simple demo MSCOMM project to VB.NET. We have thread closure.

I wanted to post the zip file of the VB.NET project in this post for the
benefit of anyone who is interested, but the file size is 54 kilobytes --
rather large for the PICList -- I don't want to upset anyone, but if the
PICList administrators say it's ok, I'll post it as an e-mail attachment.

Thanks for everyone's help and time. You all are very kind -- and patient!

Much obliged,

Ken Pergola




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