How can I get rid of -200492 error in Delphi?

Question

I am using Delphi for my developement. Earlyer, old Ni-DAQ and a MIO-16-E1 served as input device. Now the new one, M6221 works only with NI-DAQmx. So i had to convert to C routines into pascal. Anyway i wrote the following code:
status := DAQmxCreateTask ( '',taskHandle );
showmessage('Status: '+inttostr(status) );
status := DAQmxCreateAIVoltageChan(taskHandle,'Dev1/ai0','',DAQmx_Val_Cfg_Default,-0.1,0.1,DAQmx_Val_Volts,null);
showmessage('Status: '+inttostr(status) );
DAQmxCfgSampClkTiming(taskHandle,'',1000,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,1000);
showmessage('Status: '+inttostr(status) );
until here everything works, all status values are 0.
status:=DAQmxReadAnalogF64(taskHandle, -1,1,DAQmx_Val_GroupByScanNumber,
data, ct, 10, 0);
data: array[0..1000] of double;
ct : longword;
and
function DAQmxReadAnalogF64(taskHandle: TaskHandle;
numSampsPerChan: i32;
timeout: f64;
fillMode: BOOL32;
var readArray: array of f64;
var sampsPerChanRead: uint64;
arraySizeInSamps: u32;
reserved: int64
): i32; cdecl; stdcall; external nidaqmxdll;
The status variable is after calling this : -200492 as DAQmxErrorCAPIReservedParamNotNULL = (-200492);
I do get it even i use variant type in the function declaration and I pass the delphi's null variable.
What can I do?
Thanks.
Technical and Economical University of Budapest
Gulyas, Csaba
email: [email protected]

Answer 1

BLCL, if you haven't solved that one yet, rather than pass the array declaration, pass (which in Delphi is a pointer to the array), declare the array as such:
Type
TFloatArray = Array[0..8191] of Double;
pFloatArray = ^TFloatArray;
Var
ReadAI : pFloatArray;
{Other Code}
Procedure BangHeadAgainstDAQmxAPIusingDelphi(Sender : TObject);
Begin
Try
Try
// your code here
SetLength(ReadAPI, 1000 {or some relevant value});
_ReturnResult := DAQmxReadAIF64(Task, ,,, ReadAPI {don't remember the call, but this is the pointer to the data storage array},,,,); //Remember, do not dereference the array.
{code to do something with the data}
Finally
Dispose(ReadAPI);
Except
{STRONGLY RECOMMEND EXECUTING ANY DAQMXAPI CALLS IN A TRY..EXCEPT SEQUENCE}
end;
end;
end;
Hope this helps.
Jim
Oh, and just looked at your post again.
Modify your declarations, I would rewrite it as
var sampsPerChanRead: Pointer;
(note the address reference @ in front of ct)
status:=DAQmxReadAnalogF64(taskHandle, -1,1,DAQmx_Val_GroupByScanNumber, ReadAPI, @ct, 10, 0);