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Visual Basic DSP/Analog Hardware Interface Example #1

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Below is an example of interfacing off-the-shelf DSP/analog hardware to Visual Basic to produce a digital oscilloscope type display. Note the use of the DSShowHardwareSelectorDlg call to bring up a list of supported hardware.

' Declarations

Const MAXBUFLEN = 3800  ' note:  this limit imposed by use of graph control

Dim Buffer(MAXBUFLEN) As Integer  ' analog input data buffer

Dim hEngine As Integer            ' engine handle
Dim hBoard As Integer             ' board handle
Dim fBoardInitialized As Integer  ' valid if board installed and responding 

Dim uMemArch As Integer           ' type of DSP memory architecture
Dim dwBufferBaseAddr As Long      ' starting analog data buffer address

Dim nCurBuf As Integer            ' current analog I/O buffer
Dim wBuflen As Integer            ' buffer length

Dim FsDesired,FsActual As Single  ' desired and actual sampling frequency (Hz)

Dim fRunning As Integer           ' current board state in dscope example

' ***  Form Load Procedure  *******************

Sub Form_Load ()

Dim ret As Integer
Dim dw As Long
Dim BoardStr As String * 150
Dim wBoardClass As Integer
Dim dwFsMode As Long
Dim dwMemSize As Long
Dim dwFsActual As Long
Static ChanList(MAXCHAN) As Integer

 ' init some of the variables declared in general section
   hEngine = 0
   hBoard = 0
   fBoardInitialized = 0
   wBuflen = 1024
   nCurBuf = 0

   VScale = 1   ' initial display vertical scale factor
   VOffset = 0  ' initial display vertical offset
   FsDesired = 20000!     ' desired sampling frequency in Hz

 ' init local variables

   For i = 0 To (MAXCHAN - 1)
      ChanList(i) = i
   ret = DSInitToollib()  ' initialize tool library needed by Hardware 

   DSShowEngMgrStatusWindow  ' enable Engine Manager status window

 ' show Hardware Selector, let user make a board choice

   If DSShowHardwareSelectorDlg(0, BoardStr) = IDCANCEL Then
      GoTo Abort
   End If

 ' Open DSP engine

   hEngine = DSEngineOpen(ByVal DS_EO_HSM, ByVal 0&)  ' try 
Hypersignal-Macro first
   If (hEngine = 0) Then
      hEngine = DSEngineOpen(ByVal DS_EO_HSA, ByVal 0&)  ' try 
Hypersignal-Acoustic next
      If hEngine = 0 Then
         tmpstr = Str$(DSGetHWLibErrorStatus())
         tmpstr = "DSEngineOpen error code=" + tmpstr
         MsgBox tmpstr, MB_OK, "DScope Test Prog"
         GoTo Abort
      End If
   End If

 ' Assign a board handle
   hBoard = DSAssignBoard(hEngine, ByVal BoardStr, 0, 0, 0)  ' use defaults 
for bus type and I/O and Mem base addresses

 ' Initialize the board and check to see if it is responding

   fBoardInitialized = DSInitBoard(hBoard)
   If (fBoardInitialized = NUL) Then
      tmpstr = Str$(DSGetHWLibErrorStatus())
      tmpstr = "DSInitBoard error code=" + tmpstr
      MsgBox tmpstr, MB_OK, "DScope Test Prog"
      GoTo Abort
   End If

 ' interrogate engine for board type values

   wBoardClass = DSGetBoardClass(hBoard)

 ' get memory architecture

   uMemArch = DSGetMemArch(hBoard)

   If (uMemArch = NUL) Then
      MsgBox "DSGetMemArch failed", MB_OK, "DScope Test Prog"
      GoTo Abort
   End If

 ' determine sampling rate ctrl. reg. value, and actual rate (closest rate 
possible to desired);
 ' CalcSampFreq returns ctrl. reg. value directly, uses ptr to return 
actual sampling frequency (in Hz)

   dwFsMode = DSCalcSampFreq(hBoard, FsDesired, 1, ChanList(0), FsActual)  
' demo assumes 1 channel, initial value 20 kHz

 ' load executable DSP code file (usually a COFF file produced by DSP 
manufacturer's linker)

   ret = DSLoadFileProcessor(hBoard, ByVal 0&, &H1)

   If (ret = NUL) Then  ' load default file for the board type (processor 
0 only)

      MsgBox "DSLoadFile:  problem loading file", MB_OK, "Dscope Test Prog"
      GoTo Abort
   End If

 ' get the memory size, (note that this currently has to be done after a 
call to LoadFile)

   dwMemSize = DSGetMemSize(hBoard, &H1)   ' processor 0 only

 ' reset the DSP board (should already be in reset state; processor 0 only)

   ret = DSResetProcessor(hBoard, &H1)

 ' send down some important variables (needed if a default DSP Source Code 
is being used)

   ret = DSPutHVarMem(hBoard, DSP_BOARDCLASS, wBoardClass And &HFF)        
' main type in low byte
   ret = DSPutHVarMem(hBoard, DSP_BOARDSUBCLASS, Shift(wBoardClass, -8))   
' subtype in high byte
   ret = DSPutHVarMem(hBoard, DSP_OPMODE, 2)          ' Dig. Scope is mode 2

   ret = DSPutHVarMem(hBoard, DSP_FILTTYPE1, 0)       ' disable trace 1 
real-time filter
   ret = DSPutHVarMem(hBoard, DSP_FILTTYPE2, 0)       ' disable trace 2 
real-time filter

   ret = DSPutHVarMem(hBoard, DSP_TRIGLEVEL, 0)       ' free-run triggering
   ret = DSPutHVarMem(hBoard, DSP_TRIGCHANLIST, 0)

   ret = DSPutHVarMem(hBoard, DSP_BUFLEN, wBuflen)    ' buffer size
   ret = DSPutHVarMem(hBoard, DSP_HOSTBUFNUM, 0)
   ret = DSPutHVarMem(hBoard, DSP_BUFNUM, 0)

   ret = DSPutHVarMem(hBoard, DSP_CHANLIST, 0)        ' starting channel
   ret = DSPutHVarMem(hBoard, DSP_NUMCHAN, 1)         ' number of channels

   ret = DSPutHVarMem(hBoard, DSP_GAINLIST, 0)        ' gain list

   ret = DSPutHVarMem(hBoard, DSP_FSMODE, dwFsMode)   ' sampling rate 
control register (mode value)

   dwFsActual = FsActual
   ret = DSPutHVarMem(hBoard, DSP_FSVALUE, dwFsActual)  ' actual sampling 
rate (in Hz)

 ' get address of input time domain data

   dwBufferBaseAddr = DSGetHVarMem(hBoard, DSP_TIMDATAADDR)

 ' turn the board loose... (processor 0 only)
   ret = DSRunProcessor(hBoard, &H1)

 ' set the message blaster (MSGBLAST.VBX) to capture buffer ready messages 
from the DSP engine

   Buffer_Ready.hWndTarget = scope_window.hWnd
   Buffer_Ready.MsgList(0) = WM_DSPENGINE_BUFRDY

 ' register handle of graph window with engine, to receive "buffer ready" 
   ret = DSRegisterEngineMsgWnd(hEngine, DS_REMW_SETDSPDATARDYMSG, 
 ' register callback window for buffer ready messages
' tell the engine to wait for a buffer, and then start sending BUFRDY 
messages to 
registered window when analog data ready
   ret = DSWaitForBuffer(hBoard, 0, 0&, DS_WFB_POLLED)

   fRunning = True  ' set internal board state flag

 ' set initial onscreen scrollbars and buttons
   TimeBase_Scroll.Value = wBuflen
   Offset_Scroll.Value = 50  ' offset bar is in %
   RunBoard.Value = True

   Exit Sub  ' proceed with normal execution

Abort:       ' error condition / init. problem has occurred:  abort
   Form_Unload (IDOK)

End Sub

' ***  Buffer Ready Event Processing  ***************

Sub Buffer_Ready_Message (MsgVal As Integer, wParam As Integer, lParam As 
Long, ReturnVal As Long)

Dim uStatus As Integer
Dim ret As Integer

    ' transfer below illustrates two common type of DSP memory architectures

      If (uMemArch = DS_GMA_VECTOR) Then  ' vector data memory

         If (nCurBuf = 0) Then
            uStatus = DSGetMem(hBoard, DS_GM_VECTOR_DATA_X, dwBufferBaseAddr,
 DS_GM_SIZE16, Buffer(0), wBuflen)
            uStatus = DSGetMem(hBoard, DS_GM_VECTOR_DATA_Y, dwBufferBaseAddr, 
DS_GM_SIZE16, Buffer(0), wBuflen)
         End If
      Else  ' linear data/prog memory, or modified harvard arch. with linear 
data memory
         uStatus = DSGetMem(hBoard, DS_GM_LINEAR_DATA_RT, dwBufferBaseAddr 
+ nCurBuf * wBuflen, DS_GM_SIZE16, Buffer(0), wBuflen)
      End If

      If (uStatus = NUL) Then
         MsgBox "DSGetMem:  problem with point transfer", MB_OK, "Dscope 
Test Prog"
      End If
      nCurBuf = nCurBuf Xor 1  ' switch buffers

      ret = DSPutHVarMem(hBoard, DSP_HOSTBUFNUM, nCurBuf)  ' write the new 
buffer #

    ' instruct engine to wait for next buffer
      ret = DSWaitForBuffer(hBoard, nCurBuf, 0&, DS_WFB_POLLED)

    ' show 'em! (input data points)


   End If
End Sub

' ***  Waveform Data Display  *******************

Sub DisplayBufferData ()

 ' update the scope window with data currently in Buffer

   scope_window.NumSets = 1
   scope_window.ThisSet = 1
   scope_window.ThisPoint = 1
   scope_window.NumPoints = wBuflen
   scope_window.AutoInc = 1
   For i = 0 To wBuflen - 1
      scope_window.GraphData = Buffer(i) * VScale + VOffset
   scope_window.DrawMode = 3  ' Blt to screen, to avoid flicker

End Sub

' *** Form Unload Procedure  *******************

Sub Form_Unload (Cancel As Integer)
Dim ret As Integer

 ' free board, close engine if needed

   If (hBoard <> 0) And (fRunning = True) Then
      ret = DSCancelWaitBuffer(hBoard, nCurBuf)
   End If

   If (fBoardInitialized <> 0) Then
      ret = DSDisableBoard(hBoard)
   End If

   If (hBoard <> 0) Then
      ret = DSFreeBoard(hBoard)
   End If

   If (hEngine <> 0) Then
      ret = DSEngineClose(hEngine)
   End If

   End  ' shut-down app

End Sub