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Software Design Patterns
First
Sate Machine - Application Design
a state machine, is a mathematical model of computation used to design both computer
programs and sequential logic circuits. It is conceived as an abstract machine that can be in one
of a finite number of states. The machine is in only one state at a time; the state it is in at any
given time is called the current state. It can change from one state to another when initiated by a
triggering event or condition; this is called a transition. A particular FSM is defined by a list of
its states, and the triggering condition for each transition.
The behavior of state machines can be observed in many devices in modern society which
perform a predetermined sequence of actions depending on a sequence of events with which they
are presented. Simple examples are vending machines which dispense products when the proper
combination of coins are deposited, elevators which drop riders off at upper floors before going
down, traffic lights which change sequence when cars are waiting, and combination locks which
require the input of combination numbers in the proper order.
Finite-state machines can model a large number of problems, among which are electronic design
automation, communication protocol design, and other engineering applications. In biology and
artificial intelligence research, state machines or hierarchies of state machines have been used to
describe neurological systems and in linguistics—to describe the grammars of natural languages.
References:
1- Finite State Machine- Wikipedia, http://en.wikipedia.org/wiki/Finite-state_machine,
Visited on Feb 28, 2013
2- Katz- University of California, Berkley, http://wwwinst.eecs.berkeley.edu/~cs150/sp00/classnotes/katz-ch9-mod.pdf, Visited on Feb 28, 2013
Read more on state machines.
In this project, we will build a state machine that will demonstrate front panel control of
events.
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A- Menu VI
Build menu system for a sample application
Front Panel
1open a new VI
2place a cluster control
3place Boolean button (OK button) (just one for now)
4Set the button’s mechanical action to Latch When Released (right click and change)
– however, do it from properties so the preview is seen before making the choice.
5Copy and paste to create the remaining buttons
The user basically clicks a button in the cluster to trigger an application in the state machine
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make sure the order of the elements in the cluster is as shown.
Block Diagram
1- place a while loop on the block diagram to enclose the cluster and create a shift register
2- place a numeric constant to the left of the loop and set its value to -1. Connect the
constant to the shift register – this is to initialize the state machine to start at the default
state.
3- Place a case structure in the while loop. The case structure creates the states for the state
machine. Wire as shown. Add 4 more cases to the case structure.
4- Go back to the default case and do the next steps.
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5- Place a wait until so the loop executes 10 times a second.
6- Place the cluster to array function to convert the cluster of Boolean buttons into an array
of Boolean data types. This way the Boolean object at cluster order 0 becomes the
Boolean element at array index 0 and so on.
7- Place the search 1D array function and a True constant on the block diagram
8- Wire the True constant to the element input of the search 1D array . Also wire the
cluster to array to the array input of the search 1D array. This allows the function to
search for a T value in the Boolean array that cluster to array returns. A true value of
any element implies that the corresponding button was clicked. The function returns a
value of -1 if no button is pressed.
9- Connect a False constant to conditional terminal of the while loop.
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10- Select the 0 from the case structure and put the one button dialog function on the block
diagram – right click it and select Create Constant to create a string constant. Enter the
exact string Login State. Wire a -1 to the case structure tunnel and a False constant to
the conditional terminal. Next to the -1, place the comment: Next State: -1 (No Event)
11- Repeat step 10 for cases 1, 2, 3. the following string constants in order are:: Acquire
Data State, Analyze Data State, View File State, and for case number 4 do the
following: wire a -1 to the case structure tunnel and place the comment Next State: -1
(No Event) also place the comment Stop the VI. Also wire a True constant to the
conditional terminal.
A summary is shown:
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Create a subfolder and name it Application
Save the VI as Menu in the application folder.
Run the VI
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B- Acquire Data VI
Goal: Build a VI that acquires, analyzes, and presents data while using error handling techniques.
Acquire Data VI
1- close all LabVIEW VIs
2- open a new VI and build the following front panel
3- make sure you adjust the scales for the waveform graphs in properties>> Display Format
and precision to be as shown on the graph
4- build the block diagram shown (NOTE: the sampling info is added on the block diagram
next)
The sampling info is added as : create>>control at the sampling info of the “sine waveform.vi”
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The front panel should look like this
run it and watch the time and frequency plots.
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Save the VI as:
Acquire Data in the application folder.
C- Enhance Acquire Data VI
The goal here is to modify a VI to use tab control along with proper user interface design
techniques.
1- Open the Acquire Data VI
2- Place a horizontal smooth box decoration on the front panel. Place the three dials, the
sampling information cluster, and the stop button on the decoration
3- Place a tab control (located in the containers palette) on the front panel. Select the time
waveform graph and place it on the first page of the tab control
4- Name the two pages of the tab control Time Domain and Power Spectrum,
respectively.
5- Click the Power Spectrum page and add the power spectrum graph to the page.
The following is what you should have so far on the block diagram.
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6- Create an icon for the VI
7- Create the connector pane and select the pattern with two inputs and one output. Connect
the output to the Time Waveform graph (do not connect anything to inputs)
8- Save the VI in the application folder as: Enhanced Acquire Data
9- Open the block diagram and modify it as shown:
And the other case:
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Note, using the case structure enhances the performance. This is the case since the Power
Spectrum operations are only performed when called for.
10 – display the front panel and run the V. Adjust the controls to change the time and
frequency waveforms.
11 Make sure tht each of the inputs has a valid nonzero values then >>operate>>make
current values default
12- Save the vi (after having shrunk the window around the needed items in the block
diagram.
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D-
State Machine with Enhanced Acquire Data
The goal is to add the Enhanced acquire data VI to the state machine application
of Part A. Read instructions carefully
1- Open the menu.vi in your application folder
2- Open the block diagram
3- Display case 1 of the Case structure and delete the One button Dialog function. Add the
Enhanced Acquire Data.VI that you created in part C.
4- Add a shift register to the border of the while loop. Connect the Time waveform output of
the Enhanced Acquire Data.VI to the right side of the shift register.
5- Initialize the new shift register you created
a. Right click the left side of the shift register and select create>>control to create an
empty Time Waveform control on the front panel.
b. Hide the waveform control by right clicking the terminal and selecting Hide
Control. This will prevent confusion to users on the front panel.
6- Modify the VI properties of the Enhanced Acquire Data VI so that it appears like a dialog
box when it is called.
a. Double click the Enhanced Acquire Data VI to open its front panel
b. Select File>>VI Properties>>Window Appearance>>then select Dialog Option
c. Click OK then save and close the Enhanced Acquire Data VI
7- Now, recall, if one case in the Case structure passes data out of the case, then all other
cases in the case structure must also send out data. Finish wiring the VI so that the data
passes through all other cases unchanged. Make sure that the data passes through other
cases correctly (see below)
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8- Save as State Machine With Enhanced Acquire Data.VI in the application folder
9- Display the front panel and run the VI
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E-
Analyze & Present Data VI
Objective: Create a VI in which you use graph cursors to select a subset of data for analysis.
1- Open the Analyze & Present Data VI found on my web site (on the course’s main
page) Save, extract the files and move the three VIs to your application folder.
2- Use the two cursors in the plot window to select a subset of data to analyze. A cursor can
move freely or be locked to the plot. You control this action using the Lock control
button at the right side of the cursor display. Use the cursors that are locked to the plot.
When the user clicks the Analyze Select Button, the VI reads the location of each cursor
and uses this information to find the DC, RMS, Frequency, and amplitude values of the
subset data.
3- Block Diagram:
4- Open and complete the following block diagram as follows:
(many of these steps are already done – but go over them to make sure you understand)
5- Right click the data terminal and select Create>>Property Node to create the data
property node. Resize the property node to four terminals. Right click the node and
select the Active Cursor and Cursor>>Cursor Index properties from the property menu.
Right click each Active Cursor property and select Change to Write from the short cut
menu. Note, the property node executes from top to bottom. The property node selects
each cursor individually and returns the index of each cursor.
6- Place the Max&Min function. This function helps determine the beginning and the
ending index of the cursor locations.
7- Place the Extract Portion of Signal Express VI, located in Signal Manipulation palette, on
the block diagram.
8- Complete the following steps to configure the dialog window for the vi as shown:
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9- Place the Amplitude and Level measurements Express VI, located in Signal Analysis
palette.
10- Configure the dialog window as shown:
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11- Place the Tone Measurements Express VI and configure the VI as shown:
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12- Place the Feedback Node, located on Functions>> Structures palette, on the block
diagram. Feedback node transfers values from one loop iteration to the next (like shift
registers)
13- Wire the cluster constant on the left of the while loop to the Feedback node initialize
terminal.
14- Place the bundle by name and expand to show 5 inputs. Complete wiring
15- Finish the VI so that the data passes from the Feedback Node unchanged through other
cases. Make sure the other cases in the structure pass data correctly. As shown:
16- Save the VI as: Analyze & Present Data.VI in the application folder.
17- Display the front panel and run the VI Move the cursors along the graph to select a
subset of data to anakyze and click Analyze Selected Subset button. The results will
appear at the right in the Analysis Results. When finished, click Return
18- Close the VI
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State Machine with Analyze and Present Data VI
To add Analyze & Present Data VI you created above to the State Machine Application
1- Open the State Machine with Enhanced Acquire Data VI you created earlier in the
application. The Front panel is already done.
2- Open the block diagram and Display Case 2 of the Case Structure and delete the One
Button Dialog function. Use Select VI to navigate the Analyze & Present Data VI
3- Wire the waveform containing the collected data to the Data input
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4- Save the file as: State Machine with Analyze & Present Data.vi in the application
folder
5- Display the front panel and run the vi. Make sure you can acquire data and analyze
the selected date
6- Stop and close
H- Analyze and Present Data with Type Definition (TypeDef) VI
In the application you are developing, you want to build around a program
architecture that includes the ability to easily edit the code in the future. Because the
Analyze & Present Data VI uses a cluster to store the analyzed data, the complexity
of editing the code increases. In this practice you will convert the cluster constant
and cluster into a strict type definition to allow you to easily add new data items to
the cluster in the future without having to rewrite the code.
Front Panel
1- Open the Analyze & Present Data VI (not the state machine …) you completed
earlier.
2- Right click the border of the cluster in the Analysis Results as shown below and
select Advanced>>Customize to open the cluster in the Control Editor.
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a. In the TypeDef. Status pull-down menu, select TypeDef. For the type
definition
b. Select File>>Save and save the type definition as Extracted Data.cti in the
application folder
c. Close the control editor. When prompted to replace the current control
with the newly created control, choose YES.
Block Diagram
Display the block diagram and replace the cluster constant wired to the Feedback
node Initializer terminal with the custom control as follows: Right Click the
border of the cluster constant, select Replace>>All Functions>>Select a VI from
the short cut menu, Select the Extracted Data.ctl
When you modify the type definition custom cluster, all other clusters connected
to it automatically update.
Add a string indicator to the type definition custom cluster as follows:
a. Right Click the cluster constant and select Open Type Def to open the
Extracted Data.ctl
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b. Add a string indicator to the cluster as shown and label it Operator
c. Select File>>Save to save changes to the control
d. Select File>>Apply Changes to update all controls and constants that are
connected to the type definition
e. Close the control editor
7- Notice now that a string indicator has been added to the cluster constant wired to
the feedback node initializer terminal on the block diagram.
8- Display the Front Panel and notice that a string indicator has been added to the
cluster indicator.
9- Display the block diagram and resize the bundle by name function to add an input
for the operator string. Right click the input and select Create >>Control. The
following block diagram should result.
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10- Display the front panel, Add the Operator Control to a terminal on the connector
pane as an input
11- Later on, information will be passed about the operator into this VI.
12- Save and close the VI
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Ensure completions of the exercise above
Exercise 1: Verify Information VI
Objective: Build a VI that demonstrates the Simple VI architecture
Front Panel:
1- Open a new VI and build the following front panel as listed below:
2- Modify the user name and password string controls by right clicking each control and
select: Limit to Single Line
3- Modify the password control: right click>>Select Password Display
4- Place a table control. Note, the table is a 2D array of strings. The first cell is element 0,0
a. Resize the table to contain two columns
b. Right click>>Select Visible Items>> uncheck Label (to hide the label)
c. Add free labels as shown for the two columns for the table
5- Enter the information as shown, save these values as default: right click the
table>>Data Operations>>Make Current Values Default
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Block Diagram:
6- Open the block diagram and build the following
Notes:
1- To add the text, it is best to put it in-line as shown. Double click, add the text, then
move it over the line. Use coloring tools to fill with no color.
2- Make sure the indexing is enabled at the while loop inputs
3- Indexing is disabled at the output to the operator
Save the VI as: Verify Information.VI in the application folder
7- Display the front panel and enter some names and passwords in the table control
8- Enter corresponding name and password for the user name and password and RUN the
VI. Make sure it runs correctly
9- On the front panel, from the menu bar >> Edit>>Make Current Values Default
10- Create an icon with two input and two output connector terminals
a. Inputs are: User Name and Password (Top to bottom respectively)
b. Outputs are: Operator and Access Granted (top to bottom)
11- Save the VI
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Exercise 2: LOGIN VI
Objective: To use local variables to initialize controls on the front panel.
1- Download the Login VI located on my web site under Lecture link into your
application folder and open it.
2- Complete the block diagram as shown and explained below:
Note: The local variables are enclosed in a single frame sequence structure and the
empty string constant is wired to the border of the while loop. This ensures that both
local variables are updated before the while loop starts.
a- Create Login Name local variable. Set to Write. It is designed to reset the login name
to an empty string
b- Create Password local variable and set to write
c- Connect an empty string constant as shown
d- Create the Login Name Property Node by right clicking the Login Name terminal and
selecting Create>>Property Node. Select the Key Focus property. Right click the
property and select Change to Write. Wire a True Boolean to the Key Focus
e- Place the Verify Information VI you created earlier today and connect as shown.
f- Save the VI
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3- Display the front panel and run the VI Notice, the login name and password reset to
empty strings when you start.
4- Resize the front panel to include ONLY the necessary objects, use decorations to
improve the appearance as shown
5- save the VI
6- Close the VI
Exercise -3: State Machine with Login VI
In this VI you add more functionality to the final application.
Front Panel:
1- Open the State Machine with Analyze & Present Data VI you completed last time
Modify the front panel to look as shown by placing a string indicator and a square
LED.
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Block Diagram:
2- Open the block diagram and modify case 0 by:
a. Delete one button dialog function
b. Place the login VI you completed earlier
Complete the empty string connection, place the false constant to initialize the Access
Granted LED to OFF
Add, as shown, two additional shift registers since the VI needs Operator and Access
Granted information in subsequent loop iterations. By using the shift registers, only case
0, in which the login vi runs, can change the operator and access values.
3- Write the operator and Access Granted straight through the other cases in the Case
structure as shown.
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4- Modify Case
(-1) as shown
5- Save the VI as : State Machine with Login.vi in the application folder
Display the front panel and run the VI to test it.
Close the VI if all is well.
The remaining part is logging data and loading the data.
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i. The last completed VI is the State Machine with Login.vi.
File I/O techniques
Objectives
Gain familiarity with file I/O
Complete the State Machine application
Exercise -1 Binary File Writer
Objective: To build a VI that writes data to a binary file with a simple data formatting
Build a VI that saves data to a binary file using simple formatting scheme in which the
header for the file is 32-bit signed integer (I32) containing the number of data points in
the file. The next Exercise (2) will read this data file.
1- Open a new VI and build the following front panel.
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2- Build the following block diagram.
Most functions are found under File I/O. The File Dialog is found under Express>>Input. Do
not change anything in it, simply check the VIEW as icon.
3- Save As Binary File Writer.vi in the Application Folder.
4- Display the front panel and run the VI
When the dialog window appears, navigate to the application folder. To save the file,
enter the file name as data1.dat then ok
5- Close the VI
Exercise 2: Binary File Reader
Objective: To build a VI that reads the binary file created in previous exercise.
1- Open a new VI and place a waveform graph on the front panel (Do not place the
array indicator yet)
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2- Open and build the following block diagram
Note, on the Read from Binary File vi, must make the connections to the left, then add a double
constant (0) and THEN connect it to Data Type on that VI.
1- Edit>>Make Current Values default
2- save the VI as Binary File Reader
3- Run the VI, when prompted, navigate to the file you saved earlier and click on it.
4- You should obtain the same graph generated in the exercise above.
5- Save and close the VI
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Exercise -3
Write to spreadsheet VI
1- on the front panel place an array with two string controls as shown
2- Build the block diagram shown --- Use Context help to gain familiarity
Save the VI as Save to Spreadsheet.vi
Run the VI, navigate to the application folder and save the file as test1.dat
once the file is written:
1- open Excel, change the File type in the pull down menu to All files
2- open the file test1.dat
3- make sure Delimited radio button is checked, then click next
4- Tab is checked, then next
5- then click finish
You should see two columns and 11 rows (including header)
Exercise -4
Create a VI to read the spreadsheet file created in Exercise -3 – Demo to instructor.
Exercise -5: View Analysis File VI
Objective: To study a VI that reads data files created by the vi Save Data to File (already given
to you to save time – you may investigate that vi at a later time.)
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Download the compressed file: View Analysis and uncompressed it. Move the
uncompressed files to the Application folder (should be two files).
1- Start with blank VI
2- Open the View Analysis File Unfinished VI found in Application folder
3- Place two definition controls that you created in previous exercises (See next instruction
for process.)
a. On the front panel, Controls>> Select a Control. Then navigate to
ExtractedData.ctl to place the type definition controls on the front panel.
b. Label the clusters as Initial Cluster and Data Cluster.
c. Make sure the Initial Cluster is a Control and the Data Cluster is an Indicator.
4- Resize the Data cluster and reorganize the data items in the cluster similar to the
following front panel
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5- Resize the window to ONLY show the Data Cluster and the Return button. The Initial
cluster does not need to be seen by the user, thus cover it with the Data Cluster
6- Complete the clock diagram as shown
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Hint, when connecting the initial cluster to the open file function, right click the function
and select Visible Items>>Terminals. Notice, the Dialog Type extends across the icon.
You can wire the Initial Cluster at the top or bottom of the function.
Though it is hard to see, the Initial Cluster is connected to the Record Type on the
Open File vi
7- In the False case, right click Initial Cluster and select Create>> Constant. Place the
constant in the True case and wire it to the output tunnel in the true case.
8- Save the VI as View Analysis File.VI in the Application Folder
9- Close the VI
Now, let us complete the application
A- Open the State Machine with Login VI
B- Modify Case 3 as shown in the block diagram
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Save the VI as Completed Application.VI in the Final1 folder.
Display the front panel and run the vi
Go through all of the choices.
Demonstrate Successful Operation