Hi Jim,
Thank you for your response.
In case someone else comes across the same problem (lack of MemoryOptimized methods in CounterReader), I will post here my workaround, which involves building a C DLL to expose the DAQmx C API, and then calling it via platform-invoke from C#. Note that the C# digs into the internals of the Task object, so don't be suprised if it breaks in future versions of DAQmx. Disclaimers aside, this seems to work correctly on version 9.0.
/* C code: Compile to CWrapper.dll, depends on static library nidaqmx.lib */
#include <NIDAQmx.h>
dllexport int32 __CFUNC ReadCounterU32 (TaskHandle taskHandle,
int32 numSampsPerChan, float64 timeout, uInt32 readArray[],
uInt32 arraySizeInSamps, int32 *sampsPerChanRead)
{
return DAQmxReadCounterU32(taskHandle, numSampsPerChan,
timeout, readArray, arraySizeInSamps, sampsPerChanRead, NULL);
}
// C# code
using System;
using System.Reflection;
using System.Runtime.InteropServices;
using NationalInstruments.DAQmx;
[DllImport("CWrapper.dll")]
extern static int ReadCounterU32(IntPtr taskHandle, int numSampsPerChan,
double timeout, uint[] readArray, int arraySizeInSamps,
out int samplesPerChanRead);
unsafe static IntPtr GetTaskHandle(Task t)
{
var pTaskField = typeof(Task).GetField("m_pTask",
BindingFlags.Instance | BindingFlags.NonPublic);
object asObj = pTaskField.GetValue(t);
return (IntPtr)Pointer.Unbox(asObj);
}
// can now read from a counter Task by first getting its IntPtr taskHandle
// and then passing that into the extern ReadCounterU32
// according to the C API documentation
Best,
Gabriel
