error -200998

[pranav]

Hello, I have been trying to configure a task for PCI-6224 using DAQmx in measurment and automation. I have used "NI-DAQmx simulated device" option for PCI-6224. I am getting following error.

Error -200998 occurred at DAQ Assistant
Possible Reason(s):
Hardware Timed Single Point is not a supported Sample Mode for the specified Measurement Type.
Change Sample Mode and/or Measurement Type.
Conflicting Properties
Property: SampTimingType
Corresponding Value: Sample Clock
Property: Input.BufSize
Corresponding Value: 0

I want to do DI on 28 DIO lines and wants to acquire them on the rising edge of external clock connected at PFI0 and for this,  I selected followings in DAQmx task window .

Task timing

Acquisition mode : 1 sample(HW timed)

Advanced clock setting :

                   clock type : external

                   Active edge : rising

                   clock source : PFI0

What is a cause of error?

regards

Pranav

[JB]

Try following configuration : (because I'm running a french version of MAX, the terms may not be exact)

Acquisition Mode : N Samples
Number of samples : 1
Frequency (Hz) : maximum expected rate of the external clock

and reconfigure the advanced clock settings to External / PFI0 / rising

[pranav]

Hello JB,

Thanks for reply. I tried all the available options including what you have suggested. And they did work. But I would like to know that under the option you have suggested, will the data be read at the rising edge of external clock connected to PFI0  or  it will be read at fixed interval specified in "Rate" option. This is because our external clock is not periodic. It occurs randomly, and therefore I preferred 'hardware timed' ?  Why  "1 sample hardware timed"  doesn't work ? 

regards

[JB]

The reading will in fact be triggered by the external clock. If your hardware is already ready, open and run Cont Read Dig Chan-Ext Clk.vi that you will find in LV Menu >> Help >> Find Examples... >> Hardware Input and Output >> DAQmx >> Digital Measurements to test this.

At least for an AI task, the rate is used to configure the best options for the AD converter of the DAQ card according to the fastest expected rate of the external clock. To be honest, I'm not sure if it is really used for a digital task. But it is certainely a good idea to set it in the same way, all the more so since it is also set in above mentionned example. For more details, read the help for the Rate input of DAQmx Timing (Sample Clock).vi in the example.

Unfortunately I don't know why the "1 sample hardware timed" mode is not supported for a DI task like it is for an AI task.