Hi everyone - I am using NIDAQ-mx with C++ and a NI USB-6341. I am looking to use a lowpass filter on the analog ins but don't know if this is possible.
The problem is this code gets hung up when I try to use the filter.
This is what I'm doing:
if( !( retVal = DAQmxCreateTask( "", &config->taskHandle ) ))
if( !( retVal = DAQmxCreateAIVoltageChan( config->taskHandle, ss.str(), "", DAQmx_Val_RSE,
config->minVoltage, config->maxVoltage, DAQmx_Val_Volts, NULL ) ) )
if( !( retVal = DAQmxSetAILowpassEnable(config->taskHandle, "", 1) ) )
if( !( retVal = DAQmxSetAILowpassCutoffFreq(config->taskHandle, ss.str(), 500) ) )
if( !( retVal = DAQmxCfgSampClkTiming( config->taskHandle, NULL, config->frequency,
DAQmx_Val_Rising, DAQmx_Val_ContSamps, numSamplesPerChannel ) ) )
Is this the correct way to do this. Do I create the task, then the AIchannel, then the filter, then the cutoff freq, then the timing?
Any help would be much appreciated.
Solved! Go to Solution.
It seems you are doing things in the correct order (specifically addressing your final question of the post).
There are many examples that I hope were installed on your computer when you instaleld NI-DAQmx. These would be located under the Start Menu in Windows > All Programs > National Instruments | NI-DAQ > Text-Based Code Support > ANSI-C Examples. Here, one that I thought applied particularly well to your situation was in \NI-DAQ\Examples\DAQmx ANSI C\Analog In\Measure Voltage\Cont Acq -Int Clk-Cfg Filt-SCXI 114x
The applicable code here looks like:
Note: If these examples have not been installed on your computer, doing a repair of your DAQmx may fix this.
Best of luck,
The DAQmx lowpass filter properties are for devices that have configurable lowpass filter hardware, like the NI 628x, NI PXIe-4300, some NI 61xx devices, and some SCXI modules. The NI 6341 doesn't have a configurable lowpass filter.
However, the code shouldn't hang in this case, it should return an error. Did you leave out the body of each if-statement in your post, or is this a deep set of nested if-statements? Either way, the example programs that Ryan C posted should help with the error handling.
Thanks Ryan and Brad for the replies - I'm doing a :
retVal = DAQmxSetAILowpassEnable(config->taskHandle, ss.str(), 1)
which throws the exception below for error -200077
throw exception(errorBuffer);//why this hangs in my application
but I get through that errror with:
retVal = DAQmxSetAILowpassEnable(config->taskHandle, ss.str(), 0)
but then I get errors like -200452 and "specifed property is not supported by the device etc."
So it now makes sense that this won't work on the NI 6341.