Building resource name?

[RogerMont]

Hi Gang,

It's been a frustrating day.

I'm building an application driver for the PCI-6021 in native C++.  I'm using the DAQmx driver inside of it.  It appears that the driver needs C-type strings (array of type constant character) for  the "counter" specification.

All works well when I create the below and pass that to the function:

char My Counter[10] = "Dev1/ctr0";

But, I need to build the character array by casting and inserting integer variables for the device and counter numbers.

I can build strings that have the right text in them, but I haven't figured out how to cast that into a variable that will work with the command.

I know this is more of a C/C++ question, but I'll really appreciate all help.

Thanks,

Roger 

[D_Biel]

When the function help states that it requires a const char[], it is simply letting you know that it needs read-only acces. If you provide it with a char[], then it will make the conversion for you and work just fine. Below is some code I was able to run properly.

        char chan[256];
	strcpy(chan, "Dev1/ctr0");
	chan[8] = '1';
	...
	DAQmxErrChk (DAQmxCreateAIVoltageChan(taskHandle,chan,"",DAQmx_Val_Cfg_Default,-10.0,10.0,DAQmx_Val_Volts,NULL));

[RogerMont]

Hi,

That doesn't help me.

I've also been able to build a string, inserting a char literal, using the "strcat()" function.  The problem is that the device number gets passed in as an integer (this driver must be compatible with existing software).  I can implicitly cast that by this code:

int MyIntArg = 1;

char MyChar = MyIntArg;

Then replace the character:

MyCounter = "Devx/ctr0" ;

MyCounter[3] = Mychar;

This compiles without error, but the counter doesn't run.  It only runs when character literals are used.  So far, I haven't figured out what the issue is.  When the function doesn't run, it returns -200220, which seems to be a type exception error.

I appreciate all help.

Roger

[RogerMont · Accepted solution]

Eureka!!

I found a workaround.

I create an array of character literals:

char Numbers[9] = {'1','2','3','4','5','6','7','8','9'};

int MyIntArg = 1;

Then replace the character:

MyCounter = "Devx/ctr0" ;

MyCounter[3] = Numbers[MyIntArg -1];

Whew!  On to the next problem!

Roger