TAU
2008-07-12 02:40:06 UTC
Hi,
I am working with M series DAQ PXI 6259,and I want to generate digital waveform on the Port 0 DIO lines.What I did is as follows:
1.Create an AO task and a DO task in NI-DAQmx Tasks.
2.In AO task,select continuous sample Generation Mode,configure the parameters Samples to Write and Rates as 100 and 1k respectively,other parameters take the default values,then run this task.
3.In DO task,select continuous sample Generation Mode,configure the parameters Samples to Write and Rates as 50 and 1k respectively.In Advanced Timing tab,select External Sample Clock Type and ao/Sample Clock as the Clock Source,other parameters also take the default values,then run this task and I get the following warning:
Warning 200015 occurred at DAQ Assistant
Possible Reason(s):
Measurements:While writing to the buffer during a regeneration,the actual data generated might have alternated between old data and new data......
Reduce the sample rate,use a larger bufffer,or refer to documentation about DAQmx Write for information about other ways to avoid this warning.
Then I change the parameter Samples to Write in DO task to 100 as the warning clued and run task again,it works OK.I watch the waveform through the oscillograph and found that the frequency of the continuous digital waveform generated is determined by the ao/Sample Clock (equal to the ao/Sample Clock frequency divided by 2),which is what I expected.
Could you tell me that why I get the warning?And what is the mechanism it works with between the buffer and the DO waveform generation FIFO?Further more,what are the meanings of the parameters Samples to Write and Rates in DO task?I am being disturbed by these problems and looking forward to your help.
Thanks.
I am working with M series DAQ PXI 6259,and I want to generate digital waveform on the Port 0 DIO lines.What I did is as follows:
1.Create an AO task and a DO task in NI-DAQmx Tasks.
2.In AO task,select continuous sample Generation Mode,configure the parameters Samples to Write and Rates as 100 and 1k respectively,other parameters take the default values,then run this task.
3.In DO task,select continuous sample Generation Mode,configure the parameters Samples to Write and Rates as 50 and 1k respectively.In Advanced Timing tab,select External Sample Clock Type and ao/Sample Clock as the Clock Source,other parameters also take the default values,then run this task and I get the following warning:
Warning 200015 occurred at DAQ Assistant
Possible Reason(s):
Measurements:While writing to the buffer during a regeneration,the actual data generated might have alternated between old data and new data......
Reduce the sample rate,use a larger bufffer,or refer to documentation about DAQmx Write for information about other ways to avoid this warning.
Then I change the parameter Samples to Write in DO task to 100 as the warning clued and run task again,it works OK.I watch the waveform through the oscillograph and found that the frequency of the continuous digital waveform generated is determined by the ao/Sample Clock (equal to the ao/Sample Clock frequency divided by 2),which is what I expected.
Could you tell me that why I get the warning?And what is the mechanism it works with between the buffer and the DO waveform generation FIFO?Further more,what are the meanings of the parameters Samples to Write and Rates in DO task?I am being disturbed by these problems and looking forward to your help.
Thanks.