Measurement Computing LabVIEW VIs - Manual (Page 11)

How to Start a VI from Scratch
With the exception of channel and device configuration VI’s, mandatory VI’s can be found under
Acquisition Setup and Control >> Acquisition Control Palette . The Howto #1 Simple Acquisition,
shows the minimum requirements for an acquisition [using DaqIO LabVIEW support VI’s].
Required VI’s for all VI’s for initialization and closure :
COMM INIT : Initializes the DaqIO LabVIEW support (Must be first)
COMM CLOSE : Closes the DaqIO LabVIEW support and releases any resources utilized
(Must be last)
Required VI’s for synchronous operation:
SCAN CONFIG : Sets Scan rate and other scan specific parameters
ACQ ARM : Depending on the trigger method can either immediately start a scan or wait
for a specific trigger condition to occur.
READ SCAN : Once the acquisition has commenced this will retrieve specified amount of
data from the acquisition buffer.
VI’s for Asynchronous operations:
With the exception of Digital IO, asynchronous operations will have
and associated start and stop VI’s. The start, stop and update VI’s
are universal for all configured voltage output channels. This is true,
regardless of device type.
Digital IO VI’s will have only read and write VI’s.
Each of these VI’s has a “Channel Names” connection that must be
wired to determine what channels the operation will be performed
on.
Trigger VI’s:
A method of triggering the acquisition must be provided within your VI. The VI’s are
separated into three groups simple, analog, and digital.
SIMPLE : Generally immediate trigger or TTL trigger starts with manual or scan count
based stops.
ANALOG : Uses individual analog channel voltages or values to start or stop and
acquisition.
DIGITAL : Uses the value of a digital port to start or stop an acquisition.
Advanced triggering can be accomplished by combining the above VI’s. See the various
triggering examples in the “Howto” example section for details.
DaqIO LabVIEW Support VIs User’s Guide 877894 11