NI-DMM 2.9 driver error handling

[danzimmer]

Hi,

I am using the NI-DMM 2.9 instrument driver to control a PXI-4065 DMM.  My code is written in C++

The following doesn't work correctly:

errNum = niDMM_GetError(hHandle, errcode, bufSize, errDescrip);       // This function returns status = 85

I attempt to retrieve the error message that corresponds to errcode 85 with the following call:

status = niDMM_error_message(hHandle, errNum, sErrMsg);             // This function returns status = 0 but the driver doesn't store any data in sErrMsg and it is left pointing to null.

I believe that error codes > 0 are warnings and error codes < 0 are errors.  A few warnings are defined in nidmm.h, but not one for 85.  What is this warning and why doesn't the driver return a description for it?  I don't have the hardware yet and am debugging my code with the DMM set up in simulation through MAX.  I wonder if the warning is related to this?

Thanks a lot,

Dan

[danzimmer]

Sorry, there's a typo in my last post.

errNum = niDMM_GetError(hHandle, errcode, bufSize, errDescrip);       // This function returns errNum = 85

Sorry for any confusion.

[kirsch]

Hello,

What are the values you are passing for variables bufSize and errDescrip?

In order for you to know how much memory to allocate for the ViChar* errDescrip that will get returned by the driver, you should call this function with bufSize = 0 and VI_NULL for errDescrip. The function then returns the number of bytes needed in order to fit in the full error description.

Allocate the memory for errDescrip.

Then you call niDMM_GetError again, this time passing the value returned on the first call for bufSize, and the allocated string for errDescrip.

Hope this helps.

Marcos 

[danzimmer]

Hi Marcos,

Thanks for your reply.  I should have posted the values that I was passing because that isn't the problem.  It is a very good idea to implement one's code as you noted to make sure that you don't get run time memory overruns.

The problem isn't with the call to niDMM_GetError.  That function returns with errcode = 0 and no string in errDescrip.  That part is fine.  The problem is that errNum = 85, which I presume means that a warning occurred when the driver called niDMM_GetError().  I passed the return code from niDMM_GetError (85) to niDMM_error_message to get the description for code 85, and that's when the problem occurs.  niDMM_error_message() returns status = 0, which indicates that it was successful, but sErrMsg doesn't contain a string to identify what code 85 means.  In other words, the driver returned error code 85, but it doesn't return a string that describes what that means.  I hope that I explained the issue better this time.

Thank you,

Dan

[kirsch]

That's interesting. Would it be possible for you to attach a little C example that reproduces the problem so I can try it and debug it? 85 does not sound like a warning that NI-DMM would return, as it does not fall within the range specified by IVI.

Marcos