Internally Routing Counter Signals in LabVIEW
Primary Software: Driver Software>>NI-DAQmx
Primary Software Version: 8.3
Primary Software Fixed Version: N/A
Secondary Software: LabVIEW Development Systems>>Full Development System
Hardware: Multifunction DAQ (MIO)>>M Series
Problem: I want to route the output signal of one counter to the source/gate of another counter on the same card or to a specific PFI line. Can I do this without externally connecting the two pins?
Solution: Routing the output of one counter to the source of another counter should be done using property nodes and/or DAQmx Signal Routing.
Routing Example 1 Property Nodes:
- Create a task for the second counter using the DAQmx Create Channel VI (An example of a basic counter task can be found in the NI Example Finder)
- Before the DAQmx Start Task VI, if the task is finite then before the DAQmx Read VI, add a property node to the task.
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You can change the source of the signal to measure on the counter circuit from this property node. Go to Counter Measurement»Measurement Being Performed (i.e. Frequency)»Input Terminal. This is shown in Figure 1.
NOTE: It is important you pick the proper measurement, because different measurments use the counter circuit different ways. Count edges means the signal being measured is connected directly to the counter source pin. While period measurement has the signal being measured connected to the gate pin of the counter.
Figure 1: Input Terminal Selection
- Right click on Input Terminal and select Change to Write
- Right click on the input node for Input Terminal and select Create»Constant
- Right click on the input terminal constant and select I/O Name Filtering...
- On the Graphical User Interface that comes up select Include Advanced Terminals.
- Click on the pull down arrow on the contant and select Ctr1InternalOutput. This is assuming you want to connect a signal being generated by Ctr1. Select a different number if you want to route the signal in from a different counter. The channel and terminal setup should appear as in Figure 2. In particular the channel type must match the input terminal type. In this case they are both period.
Figure 2: Counter Signal Routing Block Diagram
Other parts of the counter besides the signal input pin can be rerouted on the board as well. To see these choices you can check through the channel and read and write property nodes and see what aspects of the counter signal and timing can be rerouted. Please also look at the related link about internal route availiblity.
Related Links: KnowledgeBase [3WRGIUOC]: How Can I Know What Internal Routes are Available on My Device?KnowledgeBase [368DT8MV]: Using DAQmx Export Signal to Share Counter Pulses over RTSI
Attachments:
Report Date: 07/01/2007
Last Updated: 03/27/2008
Document ID: 4B0LUTAC
