Summary: In this exercise, the objective is to control the digital I/O lines on the DAQ device. Complete the following steps to complete a VI that turns on the LEDs of Port 0 on the DAQ Signal Accessory based on the digital value set on the front panel. Each LED is wired to a digital line on the DAQ device. The lines are numbered 0, 1, 2, and 3, starting with the LED on the right.
1 to the LED
digital line turns off the LED. Writing a 0 to the LED
digital line turns on the LED.
Digital Example VI, located in the
C:\Exercises\LabVIEW Basics I directory, and
modify the block diagram as shown in Figure 1.
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DAQ Assistant Express
VI, located on the Functions>>Input
palette, in the While Loop. Complete the
following steps to configure the counter to perform event
counting.
Digital I/O>>Port Output for the
measurement to make.
Dev1>>port0 for the physical
channel and click the Finish button.
Digital Output Port Task
Configuration dialog box that appears, select
Invert All Lines In Port because the LEDs
use negative logic.
OK button to close the
configuration dialog box. All of the settings
specified for the task are saved internally in the DAQ
Assistant VI.
Build Array function,
located on the Functions>>All
Functions>>Array palette, on the block
diagram. Wire the Build Array function to the
DAQ Assistant. Complete the wiring of the block diagram.
The Boolean buttons on the front panel are stored in an
array to simplify the code. The Array Subset
function extracts only the first four elements in the
array. The output of the array subset needs to be reversed
because element 0 of the array is the most significant
bit. The array is then converted to a number with the
Boolean Array to Number function, and
converted into an array of one element. This value is
passed to the DAQ Assistant Express VI to
write that value to the port.
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