Understanding the "create_string_buffer" Digital_UART Statement

[Lesiastas]

Greetings,

Forgive me, but I'm not that knowledgeable in python and I'm having trouble understanding the "create_string_buffer" argument in the Digital_UART.py sample code. 
How do you declare this "create_string_buffer" statement into its VB6 equivalent?

Sincerely yours, 

Lesiastas

[attila]

Hi @Lesiastas

You can convert between VB String and byte arrays like this:
https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/strings/how-to-convert-strings-into-an-array-of-bytes
https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/strings/how-to-convert-an-array-of-bytes-into-a-string

You could also change the argument declaration in the wrapper to:
<MarshalAs(UnmanagedType.LPStr)> ByVal szRx As StringBuilder

[Lesiastas]

Hi @attila

Thanks for the advice about the VB String and Byte Arrays. I'm still having a hard time in understanding how to apply the "create_string_buffer" in VB6. Here's the code that I'm working on:
 

 Dim handle As Integer
        Dim rgRx() As Byte
        Dim cRx As Integer
        Dim pParity As Integer
        'Opening Device
        Call AD2_FDwfDeviceOpen(-1, handle)

        'Digital_Uart Rx Parameters
        Call AD2_FDwfDigitalUartRateSet(handle, 9600)
        Call AD2_FDwfDigitalUartRxSet(handle, 0)  '9.6kHz
        Call AD2_FDwfDigitalUartBitsSet(handle, 8) '8 bits
        Call AD2_FDwfDigitalUartParitySet(handle, 0) '0 none, 1 odd, 2 even
        Call AD2_FDwfDigitalUartStopSet(handle, 1) '1 bit stop length
        Call AD2_FDwfDigitalUartRx(handle, rgRx, (101 - 1), cRx, pParity) 'initialize RX reception

        'Done
        Call AD2_FDwfDeviceCloseAll()

I was just wondering, is it possible to use the Digital_UART for Receiving only?
What I mean by this is I only want to enable the Rx capability of the Digital_UART in receiving ASCII characters.

Regards

 

[Lesiastas]

Hi @attila

Sorry to be a bother, but can you help me understand how to declare this in VB6 format?

rgRX = create_string_buffer(101)
dwf.FDwfDigitalUartRx(hdwf, rgRX, c_int(sizeof(rgRX)-1), byref(cRX), byref(fParity))

Regards,

Lesiastas

[attila]

Hi @Lesiastas

Here you have a simple VB UART loopback example, TX = RX = DIO-0

Dim hdwf As Long
        
If FDwfDeviceOpen(-1, hdwf) = False Then
    Dim szError As String
    Call FDwfGetLastErrorMsg(szError)
    MsgBox("Device open failed" & vbCrLf & szError, vbExclamation + vbOKOnly)
    End
End If

Dim szTx = "Hello\n"
Dim rgTx = System.Text.Encoding.ASCII.GetBytes(szTx)
Dim rgRx(512) As Byte
Dim fParity As Integer
Dim cRx As Integer

Call FDwfDigitalUartTxSet(hdwf, 0)
Call FDwfDigitalUartRxSet(hdwf, 0)
Call FDwfDigitalUartTx(hdwf, Nothing, 0) ' initialize TX
Call FDwfDigitalUartRx(hdwf, Nothing, 0, Nothing, Nothing) ' initialize RX

Call FDwfDigitalUartTx(hdwf, rgTx, rgTx.Length)
Call FDwfDigitalUartRx(hdwf, rgRx, rgRx.Length, cRx, fParity)

Dim szRx = System.Text.Encoding.ASCII.GetString(rgRx, 0, cRx)
System.Console.WriteLine(szRx)

 

[Lesiastas]

Hi @attila

Thank you so much for that sample codes. I'll study it well to see how I can apply the Digital_Uart to be used only to Receive ASCII characters.

Regards, 

Lesiastas

[attila]

Hi @Lesiastas

For reception you only need the lines with RX.
See the other UART options, like FDwfDigitalUartRateSet, in the Python examples or the manual.

[Lesiastas]

Hi @attila

The UART project for serial reception is now working. Thank you so much for all of your help.
I just added some APIs that I need to replicate what was being done in the WaveForms GUI.
Here's the VB6 code made with your guidance:
 

Dim handle As Long
        'Dim szTx = "Try lang"
        'Dim rgTx = System.Text.Encoding.ASCII.GetBytes(szTx)
        Dim rgRx(512) As Byte
        Dim fParity As Integer
        Dim cRx As Integer

        'Opening Device
        Call AD2_FDwfDeviceOpen(-1, Handle)

        'Initializing UART
        Call AD2_FDwfDigitalUartRateSet(handle, 9600) '9.6kHz
        'Call AD2_FDwfDigitalUartTxSet(handle, 1)
        Call AD2_FDwfDigitalUartRxSet(handle, 0)
        Call AD2_FDwfDigitalUartBitsSet(handle, 8) '8 bits
        Call AD2_FDwfDigitalUartParitySet(handle, 0) '0 none, 1 odd, 2 even
        Call AD2_FDwfDigitalUartStopSet(handle, 1) ' 1 bit stop length
        'Call AD2_FDwfDigitalUartTx(handle, Nothing, 0) ' initialize TX
        Call AD2_FDwfDigitalUartRx(handle, Nothing, 0, Nothing, Nothing) ' initialize RX

        'Capturing Samples
        'Call AD2_FDwfDigitalUartTx(handle, rgTx, rgTx.Length)
        Call AD2_FDwfDigitalUartRx(handle, rgRx, rgRx.Length, cRx, fParity)

        Dim szRx = System.Text.Encoding.ASCII.GetString(rgRx, 0, cRx)
        'System.Console.WriteLine(szRx)

        'Done
        Call AD2_FDwfDigitalUartReset(handle)
        Call AD2_FDwfDeviceCloseAll()

Here's the result we came up when we connected the UART Controller to transmit ASCII characters:

Thanks for everything! More power to you and Digilent!

Regards,

Lesiastas

 

[attila]

Hi  @Lesiastas

You're welcome and thank you.

[Lesiastas]

Hi @attila

Is it possible to immediately store String values instead of Byte in the FDwfDigitalUartRx API? I created another set of code to be applied in VBA. 
Here's the code I'm working on:

Public Function AD2_FDwfDigitalUartRx(ByVal hdwf As Integer, ByRef szRx() As String, ByVal cRx As Integer, ByRef pcRx As Integer, ByRef pParity As Integer) As Integer

        Dim rgRx = System.Text.Encoding.ASCII.GetString(szRx, 0, cRx)

        Call FDwfDigitalUartRx(hdwf, rgRx, cRx, pcRx, pParity)

    End Function

But an error of:  always occurs.

So my main question is this: How can I post process the FDwfDigitalUartRx to display String data after reception?

Regards,

Lesiastas

[attila]

Hi @Lesiastas

You could change in the declaration of FDwfDigitalUartRx the argument to be <MarshalAs(UnmanagedType.LPStr)> ByVal szError As StringBuilder  as it is for FDwfGetLastErrorMsg.