1. Digital Electronics and Computer Interfacing Tim Mewes 5. Computer Interfacing – DAQ cards

2. Digital Electronics and Computer Interfacing2 5.1 Basics Data acquisition is the process of gathering a signal and digitizing it for presentation, analysis and storage on a computer Signals can be either Analog or Digital

3. Digital Electronics and Computer Interfacing3 5.1 Basics Today a wide variety of different DAQ devices are available: –PCI cards –PCMCIA cards (Notebooks) –USB solutions are becoming popular Most DAQ devices allow to acquire and create signals (Input/Output)

4. Digital Electronics and Computer Interfacing4 5.2 DAQ Setup DAQ setup can be done using the Measurement and Automation Explorer (MAX) MAX also allows to test basic hardware functionality The latest version of DAQ device drivers are called NI-DAQmx A DAQ setup configuration is called NI-DAQmx task

5. Digital Electronics and Computer Interfacing5 5.2.1 Creating a new NI-DAQmx task Open MAX Go to devices & Interfaces Select NI-DAQmx devices Choose the card you want to use for the task (NI PCI-6014) Select “Create Task”

6. Digital Electronics and Computer Interfacing6 5.2.1 Creating a new NI-DAQmx task Select the type of task you need (Digital I/O) Select whether you want to input or output data (example: Line Output) Select the physical channels you want to use (example: P0.0 – P0.3) Name the task Select Finish and then test the hardware

7. Digital Electronics and Computer Interfacing7 5.2.2 Using a NI-DAQmx task in LabVIEW Go to Measurement I/O NI-DAQmx Choose Read or Write Create a constant for the task input Select the task to be used as the constant

8. Digital Electronics and Computer Interfacing8 5.2.2 Using a NI-DAQmx task in LabVIEW Configure the SubVI to input/output data as needed The NI-DAQmx VIs are examples for so called polymorphic VIs

9. Digital Electronics and Computer Interfacing9 Polymorphic VIs Polymorphic VIs accept different data types for a single input or output terminal Polymorphic VIs automatically adapt to accept input data of different data types

10. Digital Electronics and Computer Interfacing10 5.3 Counter A counter is a digital timing device Can be used to –Count rising and/or falling edges –Measure the frequency/period of a signal –Measure the pulse width of a signal The count register stores the current count of the counter Counter gates can be used to externally enable/disable counting

11. Digital Electronics and Computer Interfacing11 5.3.1 Creating a NI-DAQmx counter task Open MAX Select “Create Task” Choose “Counter Input” Example: “Frequency” The NI PCI-6014 has two counters choose one of them

12. Digital Electronics and Computer Interfacing12 5.3.1 Creating a NI-DAQmx counter task Modify the task properties if necessary Save the settings Note the PIN to which the signal has to be connected! Make the physical connection Test it