state machine (labview programming) - wikipedia, the free encyclopedia

7/25/2019 State Machine (LabVIEW Programming) - Wikipedia, The Free Encyclopedia

1/7

01/07/2016 State machine (LabVIEW programming) - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/State_machine_(LabVIEW_programming)

State machine (LabVIEW programming)From Wikipedia, the free encyclopedia

A state machine is a type of programming technique that is used in a majority of different programming language

The state machine is especially important and flexible tool that is used in LabVIEW programming because the

coding is very easy to maintain, document and reuse. [1]

Contents

1 Introduction to state machines2 State Machines in LabVIEW

2.1 Common Devices of a State Machine2.2 Simple soda machine example

3 Benefits4 References

Introduction to state machines

State machines revolve around 3 concepts: the state, the event, and the action. The state is the position or status

that the program is at when it is working through the problem. For example a state could be waiting for the user to

do something, or running a calculation. States work to help break up the big picture and help to make everything

run smoother. Developing these wisely will help to make the state machine run more efficiently. Events are

occurrences that have specific meaning to the program itself. The example that we will be building is a soda

machine that dispenses soda after the user has inserted the correct amount of money. An event for this program

could be the money being inserted, or theperson hitting the start button. The action is how the program will react

to the particular event that has occurred. [2]

State Machines in LabVIEW

In LabVIEW, state machines are even more powerful. A state machine can help the program respond intelligently

to different types of data that the user could put in. [3]To help explain this feature we will use a simple soda

machine program to help illustrate the technique.

Common Devices of a State Machine

In LabVIEW state machines can be started by simply creating a while loop with a case structure located within thloop. The while loop can have a special constant wired to it called an enumerated constant. An enumerated

constant is a constant word or phrase is changed to a simple integer from 0 to n - 1, where n is the number of case

the user would like to have. Doing this makes programming a lot easier for the user to understand because instead

of looking at number codes they are looking at a few words describing what is going on. A state machine also

relies heavily on shift registers. A shift register is used to pass information around in a while loop, for example a

shift register will start with information that will be worked on in the loop, after the work is finished then new

value can be saved on the shift register to be used at the start of the loop next time.[4]Next all the programmer ha

to do is add tasks to each case individually. After the initial enumerated constant is created it is often worth while

to make it into a type definition (commonly referred to as type def.). Making the enumerated constant into a type
https://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/LabVIEW


2/7



This is a picture of a simple for loop located in a while loop using Enumerated constants and shift registers

def. allows

the user to

continue to

copy the

original and

re-use it in

the program,

like a normal

controlexcept with

a type def. if

you change

one of them

you end up

changing all

of them.

Type def.

allows the

program to

be muchmore robust

and making

it much

simpler to

change if

something

new needs to

be added.

Simple soda machine example

In the soda machine example we are using shift registers to pass around the total amount of money in the machine

and the enumerated constants that control which case we are in. When we look at our start case picture shown

below we can see the shift registers on the left and right side and the enumerated constants in the middle. we can

also see at the bottom of the picture there is a Tab that is used to display each individual section is being written to

as an indicator. By doing this we remove the possibility of the user getting off of the loop and locking them into th

case they are supposed to be in. When we are in the start stage of the program we want to make sure that the user

right there with the program.
https://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(End_Case).png


3/7



This is the start case from the Soda machine example

This case

holds the

user on the

start menu

on the block

diagram,shown

below,until

the user hits

the start

button. Once

the start

button is

pressed the program is then sent to the next case

(called the Insert change case).

Once in the Insert change case the user will once again be held here to continue adding money to the total they

have had so far through the use of shift registers and buttons that money every time you hit them. This is the main

case where most of the work is being done and where the soda machine is as real as possible, with out adding

actual coins, every other case has most of the work running in the background. Once the user has finished adding

money they press the Finished inserting money button to move on to the Dispense case.
https://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Start_Block_Diagram).pnghttps://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Start_Case).png


4/7



The Insert

money case

also

changeswhich tab is

being

displayed to

the Insert

Change tab

on the block diagram. Here the user can insert

money and also see how much money was through

the Total Money Inserted display.

The dispense case starts by first checking to make sure that the user has inserted enough money to buy a soda.

There is a case second case structure in this case to handle the two options of either enough money, or not enough

money. If there is enough money in the system a message box will pop up saying thank you for purchasing the

soda and then subtracts the amount of money it takes to purchase a soda from the total amount of money in the

system. If there is not enough money in the system the program outputs a new message saying that there is not

enough money and sends out all of the money that was previously inserted before moving on to the end case.
https://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Insert_Change_Block_Diagram).pnghttps://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Insert_Money_Case).png


5/7



The block

diagram for

the dispense

case and the

end case is

the same

picture. There is really nothing that the user really

has to do besides pop up messages that the program

will output.
https://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Dispense_Change_Block_Diagram).pnghttps://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(Dispense_Case).png


6/7



The end case

is a very

simple case

that works to

simply delay

the program

to allow the

user enoughtime to

check that

they have

received

their change

and picked

up their

soda. After

5000

milliseconds

(or 5seconds) the

wait timer is

used up and

the program

continues

back to the

start page to wait for another user to come by to begin the process over again.

Benefits

The state machine is often used because it is easy to quickly start up and add or remove parts of the program. Stat

machines work in a fashion as to also help keep the developer organized as they work.[5]

References

1. Bitter, Rick.LabVIEW Advanced Programming Techniques.Boca Raton: CRC Press LLC, 2001

http://www.physics.utah.edu/~jui/3620/supp/LV_Adv_Prog/2049ch03.pdf

2. Bitter, Rick

3. Bitter, Rick

4. LabVIEW Help Page from LabVIEW 2011

5. "Tutorial: State Machines," 2014, http://www.ni.com/white-paper/7595/en/

Retrieved from "https://en.wikipedia.org/w/index.php?title=State_machine_(LabVIEW_programming)&oldid=720829946"

Categories: Virtual machines

This page was last modified on 18 May 2016, at 05:53.Text is available under the Creative Commons Attribution-ShareAlike License additional terms may applyBy using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia is a registered trademark
https://wikimediafoundation.org/wiki/Privacy_policyhttps://wikimediafoundation.org/wiki/Terms_of_Usehttps://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_Licensehttps://en.wikipedia.org/wiki/Category:Virtual_machineshttps://en.wikipedia.org/wiki/Help:Categoryhttps://en.wikipedia.org/w/index.php?title=State_machine_(LabVIEW_programming)&oldid=720829946http://www.ni.com/white-paper/7595/en/http://www.physics.utah.edu/~jui/3620/supp/LV_Adv_Prog/2049ch03.pdfhttps://en.wikipedia.org/wiki/File:LabVIEW_State_Machine_example_(End_Case).png


7/7



of the Wikimedia Foundation, Inc., a non-profit organization.
https://www.wikimediafoundation.org/

state machine (labview programming) - wikipedia, the free encyclopedia

Documents