Hi,
I have a simple requirement to acquire bursts of data on AI0 using PF0 as the trigger. The trouble I am having is that I cannot get the configured task to retrigger. In other words, it triggers once only. I have attempted to use both DAQmxSetStartTrigRetriggerable and DAQmxSetTrigAttribute functions to enable retriggering but without success.
1. Using DAQmxSetStartTrigRetriggerable(hDAQTask, TRUE) I get the following error:-
Specified property is not supported by the device or is not applicable to the task.
Property: DAQmx_StartTrig_Retriggerable
Task Name: DAQ Task
Status Code: -200452
The USB6211 claims to support retriggering in the list of supported properties in the NI Device Help. Hence the commitment of more than 800USD for one unit.
2. If I use DAQmxSetTrigAttribute (hDAQTask, DAQmx_StartTrig_Retriggerable, TRUE) the task will trigger only once and results the following:-
Attempted to read a sample beyond the final sample acquired. The acquisition hasstopped, therefore the sample specified by the combination of position and offs
et will never be available. Specify a position and offset which selects a sample up to, but not beyond, thefinal sample acquired. The final sample acquired can be
determined by querying the total samples acquired after an acquisition has stopped.
Attempted to Read Sample: 20
Property: DAQmx_Read_RelativeTo
Corresponding Value: DAQmx_Val_CurrReadPos
Property: DAQmx_Read_Offset
Corresponding Value: 0
Task Name: DAQ Task
Status Code: -200278
Without a retrigger data acquisition has stopped so reading the AI buffer obviously fails.
I have resorted to stopping and restarting the task but this has an overhead of around 15ms which is not acceptable for our application.
DAQmxExecuteNoError(DAQmxStopTask(hDAQTask)); // Stop and restart DAQ task => Retrigger
DAQmxExecuteNoError(DAQmxStartTask(hDAQTask)); // This step takes around 15ms
There is another thread from 2009 which covers the subject of retriggering on an NI PCI 6132 but there appears to have been no actual resolution. See HERE...
To summarise:-
- I have attemped to run the ContAcq-IntClk-DigStart-Retrig example but this fails on DAQmxSetStartTrigRetriggerable
- I have tried the alternative DAQmxSetTrigAttribute function but this does not seem to actually enable retriggering.
- I followed the 2009 thread and found nothing additional that would be useful
Am I doing something wrong or does the USB6211 not support retriggering. Do I need to get a different device or is there a know issue?
Any help would be very much appreciated...
Tan
