GS - LOC Needle Value in VB.Net - help...

[Foppel]

Hello,

I doesn't get the Values for the Nav1 Loc and GS needle in VB.NET. I got all values (Byte, Word, LongWord, SmallInt, LongInt) but the needed value (shortInt) range from -127 to +127 not.

Dim gsneedle As Integer
Dim MyResult As Short
Dim dwResult As Byte

Call FSUIPC_Read(&HC49, 1, gsneedle, dwResult)
Call FSUIPC_Process(dwResult)
Call FSUIPC_Get(gsneedle, MyResult)

Label2.Text = MyResult.ToString

Any help appreciated...

Regards,

Dirk

[Pete Dowson]

I doesn't get the Values for the Nav1 Loc and GS needle in VB.NET. I got all values (Byte, Word, LongWord, SmallInt, LongInt) but the needed value (shortInt) range from -127 to +127 not.

The value is not a "short" (16 bit) but a signed byte (8 bit).

Dim gsneedle As Integer

Dim MyResult As Short

Dim dwResult As Byte

Call FSUIPC_Read(&HC49, 1, gsneedle, dwResult)

Call FSUIPC_Process(dwResult)

Two odd things there:

1: dwResult is a 32-bit result code, it won't fit into a byte.

2: You are correctly reading the 1 byte at offset 0C49, but into a 32-bit integer. You need to set that to zero first, or it is likely to contain rubbish in the unused 24 bits.

If you correct (2) then you will not see negative numbers -- the range will be 0 to 255. This is because the negative sign is in the single byte you have read, and will not be propagated into the other 24 bits. So to correct this you would need to OR into the 32-bit integer hex FFFFFF00 is the byte value is >= 128.

Regards,

Pete

[Foppel]

Hello Pete,

thanks for your quick response and help.

The VB.Net code

Dim gsneedle As Integer
Dim MyResult As Integer
Dim dwResult As Integer

Call FSUIPC_Read(&HC49, 1, gsneedle, dwResult)
Call FSUIPC_Process(dwResult)
Call FSUIPC_Get(gsneedle, MyResult)

If MyResult > 127 Then
    MyResult -= 256
End If
Label2.Text = MyResult

Regards,

Dirk

[Pete Dowson]

thanks for your quick response and help.

The VB.Net code

Does that work? Shouldn't you set "gsneedle" to zero before the Read, or are all variables in VB.NET zeroed for you?

Pete

[petdocvmd]

The value is not a "short" (16 bit) but a signed byte (8 bit).

Two odd things there:

1: dwResult is a 32-bit result code, it won't fit into a byte.

2: You are correctly reading the 1 byte at offset 0C49, but into a 32-bit integer. You need to set that to zero first, or it is likely to contain rubbish in the unused 24 bits.

If you correct (2) then you will not see negative numbers -- the range will be 0 to 255. This is because the negative sign is in the single byte you have read, and will not be propagated into the other 24 bits. So to correct this you would need to OR into the 32-bit integer hex FFFFFF00 is the byte value is >= 128.

Pete,

VB.net has no signed byte data type. You have to use a short which covers -32768 to +32767.

VB.net "number" variables are initialized to zero implicitly upon declaration (and booleans to false, strings to 'Nothing', etc)(yeah I know, programmers should be allowed to fall on their own swords ).

I've been buried in 8051-variant assembler these days - feels kinda good mucking around in the"down 'n' dirty" stuff :-)

Scott

Scott L. Fausel, VMD

Integrated Flight Systems

[Pete Dowson]

VB.net "number" variables are initialized to zero implicitly upon declaration (and booleans to false, strings to 'Nothing', etc)(yeah I know, programmers should be allowed to fall on their own swords ).

Ah, right. I was only being careful because, in C, only static (global) storage is initialised, the dynamic (local) stuff is just space reserved on the stack.

Regards,

Pete