![labview while loop labview while loop](https://i.stack.imgur.com/DiHNd.png)
The consumer process is delayed until data is available in the queue, making queues a mechanism for synchronization. Queues pass data between two processes: one process pushes data onto a queue (enqueue) and the other consumes data from the queue (dequeue). Because of this flexibility, the Notifier is a much improved Occurrence. This feature can simplify the structure of an embedded control application.Īlso, the data type in the Obtain operation can be anything available in LabVIEW, such as a cluster, array, or variant. However, if multiple “Send” operations execute prior to a “Wait”, the last data written to a “Send” wins. If the ‘Wait on Notification’ is used in many places within various block diagrams, all of them will retrieve the same data passed by the ‘Send Notification’ operation. The ‘Wait on Notification’ has a timeout option and the ‘ignore previous’ similar to the Occurrence. And, yet, the main VI affects the execution of the slave by forcing the slave to delay execution until the main alerts it via the Notifier.Īlso note that the use of the global ‘Stop?’ flag is not required here because the ‘Wait on Notification’ will error when the Notifier is destroyed in the main VI. Note that there is no wiring between this loop and the main loop. When the Notifier is set, the Message Box displays the string passed by the Notifier. The slave loop then simply waits for the Notifier to be set. Note that the Notifier is obtained with the same operation that creates the Notifier within the main VI (in fact, it’s not really clear which Obtain executes first). This second block diagram is from the ‘Notifier Example Slave’. This Boolean must be set TRUE to force the destruction of the Notifier even though it is still in use within the slave VI. Note the non-default use of the ‘force destroy?’ Boolean. When the main VI is stopped, the Notifier is destroyed. Upon each ‘Set’ event, the Notifier is set and the string “Set Pressed” is passed. The main VI waits on a button press events from the ‘Set’ button. That’s because the slave VI takes advantage of the fact that the Notifier can be obtained by a lookup from its name. The subVI ‘Notifier Example Slave’ is placed on the main block diagram with nothing wired to it.
![labview while loop labview while loop](https://i2.wp.com/www.ni.com/images/labview/2010/neutral/graphical_while_loop.jpg)
The data type associated with this Notifier is a string. The Notifier is created on the left side of the diagram with the name “Demo”. Plus, they can pass data from the producer to the consumer and are thus defined with a data type.Īn example of usage follows in the 2 block diagrams.
Labview while loop code#
They can also be named which allows a Notifier to be found elsewhere in your code without needing a connecting wire. Notifiers have the Timeout and Ignore Previous features similar to Occurrences. Notifiers have basic operations for Obtain, Send, Wait, Status, and Destroy. Notifiers are found in the sync palette as shown next. In fact, NI recommends that you use these instead of Occurrences. Notifiers are a sophisticated version of Occurrences. They are event-driven and consume very little CPU usage: your paused code essentially goes to sleep. The beauty of these tools is that they don’t need to be polled. Another blog post will cover the second group. The second group manages access to a piece of code based on the actions of multiple data sources. So, I’m just going to talk about Notifiers. Note that Notifiers are supersets of Occurrences, since they can pass data, whereas Occurrences cannot. For example, perhaps you need to wait on a temperature controller for an aircraft hydraulic system to reach a certain pressure before moving a part and the pressure is being controlled in a parallel loop. The first group pauses execution of a piece of code until data is available or a condition is met. LabVIEW offers several types of synchronization tools.