Best way for read and write?

[mori64]

Hello

I'm working on project with labview .

with this program i connecting PC to the MCU through sreial RTU modbus .

in this program there are some data need to be read and some data need to write .

what i need is most of my time reading polet exuted exept when some of  control element (like edit box) has changed by user .

when ever some thing changed by user write polet excuted .

now what is the best way to do this ?

Best Regards.

[crossrulz · Accepted solution]

Event Structure inside of a While loop.  With the event structure, you detect the changing of values and send the appropriate commands.  You could use the Timeout case for reading the status from the MCU.

[mori64]

Thanks crossrluz

I did it but with this way  while loop's stop button dosen't work ! 

Best regards

[crossrulz]

Code?  It is impossible to debug your application without it.

[mori64]

sorry you are right .

[crossrulz]

It works for me.  Granted, I had to remove all of the Modbus communications in order to run it.  Are the statuses taking a long time to come in?  I would also recommend using an event case for the stop button.

[Bob_Schor]

Here is a good "rule" that will help your LabVIEW coding -- NEVER use a Stacked Frame!  If you want to do a multi-step procedure on a set of variables, use a State Machine, a While loop inside of which is a Case Statement, with something wired to the Case Selector that "steps" you through the various steps.  Use Shift Registers on the While loop to pass the variables seamlessly from one Case to the next (none of these "the wire goes out on this edge and pops back in over there" guesswork with Stacked sequences).  Note that you can also use a For loop and wire the Loop Index to your Case Selector to do Steps 0, 1, 2, 3 (you'll need to add a "default" case in this model).  Here is a snippet, where the Enum has been given the less-than-descriptive names "Step 1", "Step 2", etc.  If using a While, wire the last Case to the Stop indicator, of course.

Here is a Very Simple example.

Bob Schor

[mori64]

Thanks 

I think my USb->Serial had problem after restart my pc my code work too.

this is  my Secend project with labview.  i'll be happy if you have any comment about my code .

best Regards .

[mori64]

Thanks Bob 

What uou said sound complicated to me .

i'm trying to undrestand your solution .

i'll be happy if you upload sample program .

[crossrulz]

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mori64 wrote:

What uou said sound complicated to me .

i'm trying to undrestand your solution .

i'll be happy if you upload sample program .

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State Machine