Welcome! Workshop 3 of 7 Today's Topics Review of Workshop 2 Loops While For Auto-indexing Shift registers Case Structure Review Question 1 True or False? 1. Arrays can contain only one data type. 2. An array must contain at least one element. 3. The Bundle function can be used to add elements to a cluster. 4. Clusters can contain both controls and indicators within the same shell; however, arrays cannot. 5. It is possible to have clusters containing arrays as well as arrays containing clusters. 3 Review Question 1 True or False? 1. Arrays can contain only one data type. TRUE 2. An array must contain at least one element. FALSE 3. The Bundle function can be used to add elements to a cluster. FALSE 4. Clusters can contain both controls and indicators within the same shell; however, arrays cannot. FALSE 5. It is possible to have clusters containing arrays as well as arrays containing clusters. TRUE 4 Review Question 2 The Error Cluster contains which of the following? a) Boolean b) Array c) String d) Numeric e) Cluster 5 Review Question 2 The Error Cluster contains which of the following? a) Boolean - status b) Array c) String - source d) Numeric - code e) Cluster 6 Review Question 3 An enumeration is a list of ___ and ___ pairs and acts like a ____ to the computer and ____ to the user. a) integer, string, integer, string b) Boolean, string, boolean, string c) Boolean, integer, boolean, integer d) integer, string, string, integer 7 Review Question 3 An enumeration is a list of ___ and ___ pairs and acts like a ____ to the computer and ____ to the user. a) integer, string, integer, string b) Boolean, string, boolean, string c) Boolean, integer, boolean, integer d) integer, string, string, integer 8 Review Question 1 If I add a new element to an enum that is saved in a *.ctl file, how would the file need to be saved in order to update all of instances a) Custom control b) Strict Type Definition c) Type Definition Review Question 1 If I add a new element to an enum that is saved in a *.ctl file, how would the file need to be saved in order to update all of instances a) Custom control b) Strict Type Definition c) Type Definition Review Question 2 Which of the following always remain unique to each instance? a) Label b) Default value c) Size d) Data type e) Representation (numerics) f) Description Review Question 2 Which of the following always remain unique to each instance? a) Label b) Default value c) Size d) Data type e) Representation (numerics) f) Description Review Question 3 True or False? A custom control can only be used for the project within which it was created. Review Question 3 True or False? A custom control can only be used for the project within which it was created. FALSE Loops • Use loops when you want to repeat a section of code • Types: • While – repeats until a condition is met • For – repeats for X number of iterations 15 While Loops • terminal counts the number of iterations; zero indexed • Always runs at least once (therefore, really a do-while loop) • Runs until stop condition is met • Stop if TRUE • Continue if TRUE While Loop Iteration terminal Conditional terminal For Loops • • i = zero indexed N = one indexed i Terminal counts iterations Runs according to input N of count terminal Count terminal For Loop Iteration terminal Creating a Loop 2. Enclose code to be repeated 1. Select the structure 3. Drop or drag additional nodes and then wire Demonstration: Creating a Loop Building Arrays with Loops Auto-Indexing Enabled Loops can accumulate arrays at their boundaries with autoindexing Wire becomes thicker 1D Array For loops auto-index by default While loops output only the final value by default 0 1 2 3 4 5 Auto-Indexing Disabled Wire remains the same size Right-click tunnel and enable/disable auto-indexing 5 Only one value (last iteration) is passed out of the loop Auto-Indexing Input • If an array is passed into a For Loop and auto-indexing is enabled, the number of elements in the array determines the number of iterations of the For Loop (therefore, you are not required to wire the N terminal) • If the iteration count terminal is wired and arrays of different sizes are wired to auto-indexed tunnels, the actual number of iterations is the smallest of the choices. Shift Registers - Access Previous Loop Data “Up and around the loop” Left terminal provides stored data at beginning of next iteration Right terminal stores data on completion of current iteration • Come in pairs that are always aligned with each other • Available at left and right borders of loop structures • To create: • Right-click the border and select Add Shift Register • Right-click an existing tunnel, select Replace with Shift Register, and click the opposite loop border to create other half of pair Shift Registers in action Value 15 Initial Value Before Loop Begins First Iteration Second Iteration Last Iteration Stacked Shift Registers • Registers remember values from multiple previous iterations and carry those values to the next iterations • Values “bump down” with each iteration • To create: • Right-click » Add Element • Expand the left side register (down arrows) up or down by dragging the small square when the mouse is a double arrow Initial Value Note: Still only 1 register on right side Shift Registers - Uninitialized Run once VI finishes Block Diagram Run again 1st run 2nd run Initialized Shift Register Output = 5 Output = 5 Not Initialized Shift Register Output = 4 Output = 8 Demonstration: Operation of a Shift Register Case Structure Case Selector Label Selector Terminal • Have two or more subdiagrams or cases • Execute and displays only one case at a time • An input value determines which subdiagram to execute • Similar to case statements or if...then...else statements in text-based programming languages Case Structure: Inputs • You can create multiple input tunnels • Inputs are available to all cases, but do not have to be used in all cases Case Structure: Outputs • You can create multiple output tunnels • You must define each output tunnel for each case, otherwise (1) • Wire every case (2) (2) (3) • Right-click » Use Default If Unwired (3) Data Type Default Value Numeric 0 Boolean FALSE String Empty Case Structure Case Structure If the error cluster is wired to the selector, the border of the case structure automatically turns red or green for the error and non-error cases, respectively Holy automatic coloring, Batman! Demonstration: Creating a Case Structure and Adding a Case Diagram Disable Structure Use to disable a section of code on the block diagram Multiple subdiagrams possible – maximum of one enabled Disabled subdiagrams appear grayed out Great tool for troubleshooting – don’t have to re-write code Conditional Disable Structure Use to define conditions that indicate which code on the block diagram executes Examples: If running as an executable, then programmatically close LabVIEW when VI finishes If running on Windows, look for file here; if running on Mac OSX then look here. Events Event — An asynchronous notification that something has occurred • Events originate from the user interface, external I/O, or other parts of the program Example events: • Button click • Value change • Mouse over • Key press 35 Event Structure Event Structure — LabVIEW’s programmatic tool for handling events. • Therefore, execution of code can be dependent on whether or not an event has occurred • Waits for an event to occur indefinitely, unless configured to timeout. 36 Parts of an Event Structure • Event Data Node Identifies the data Timeout Event Selector Label LabVIEW provides when the event occurs; Event Data Node Event Filter Node similar to the Unbundle By Name function • Event Filter Node Identifies the subset of data available in the Event Data node that the event case can modify 37 Notify and Filter Events Notify Events • User action has already occurred • LabVIEW has processed the event • Available only in the Event Data node Filter Events • User action has already occurred • LabVIEW has NOT processed the event • Allows you to override default behavior for event • Available in the Event Filter node and Event Data node To Configure an Event Structure… Right-click the border and select Edit Events Handled by This Case Configuring Event Structures Configured Events Event Sources Events Notify and Filter Events in Config. Window Notify Events (green arrow) User action has already occurred Filter Events (red arrow) User performed action but event is not processed. Allows you to customize event handling. Using Event Structures • Normally used in a While Loop • Control/Indicator the event configured for is often placed inside that event case • Event structure handles exactly one event per iteration • Sleeps when no events occur Event Structures Tips • If no timeout is configured and an event never occurs – stuck waiting indefinitely, must abort VI; therefore, wire the timeout terminal with a value other than -1 (at least while developing) • “heavy” code within the Event Structure causes the front panel to lock up, often confusing the user – try to keep code in an event case to a minimum Demonstration: Configuring an Event Homework • Homework 3 is post at ni.com/mst • Create a Game • Student Zone has a lot of ideas • Email to mst.labview@gmail.com