How to use shared variables with native c programs

Hello
What is the way to use shared variables with native c programs?
I have a c/c++ program that uses the NIDAQmx C-API to perform measurements. Now I want to communicate to a LabVIEW program via shared variables.
Is there a C-API for shared variables as there is for the NIDAQmx functionality? Where can I find further documentation? The document "Using the LabVIEW Shared Variable" mentions that one "can read and write to shared variables in ANSI C", but there are no hints about how and where to look.
Thanks in Advance

Hi user42,
with CVI 8.0, you cannot create or configure shared variables. However, you can read or write to an already configured LabVIEW 8.x shared variable from CVI using the DataSocket API.
In order to do this you need to have and DataSocket 4.3 or higher installed.
Here's a forum post about using the DataSocket functions a LabVIEW Shared Variables:
http://forums.ni.com/ni/board/message?board.id=180&message.id=24569&requireLogin=False
With CVI 8.1 and Measurement Studio 8.1 it's possible to use Shared Variables via the Network Varaiable Library (check out the end of the "Network-Published Shared Variable" section within the "Using the LabVIEW Shared Variable" documentation and the following link).
Datasocket with LabWindows/CVI and LabVIEW Real-Time:
http://digital.ni.com/public.nsf/allkb/CC4343488413A2F586256E6200099638?OpenDocument
Daniel
NIG

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How to use shared variables?

Hello..
Can anybody please guide me in using shared variables... I'm learning LabVIEW 8.5.... But did not understand how to use shared variables... I tried to read web pages regarding shared variables but got confused.... So anyone can please help me...?
Thanks for any help from you...

You will have to give us the whole picture. What is your client computer; a PAC, desktop etc? What are you running on the client computer; a VI or an executable? Where are you going to deploy your library? On the host machine or the client machine?
If I assume that you are running a VI on the client machine and are depolying the library on the host, all you have to do is to create another shared variable and bind it to the variable on the host machine. You can do this by checking the Bind to Source option when creating the variable and browsing to the network item in options. Be sure to have the library deployed on the host side before you attempt to do this otherwise you won't be able to find the variable.
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Peter,
Thanks for the reply. I have actually solved that problem. I realized that the Modbus server address has to be the same as the controller's Modbus address.
I have, however, run into another problem. Perhaps you could help me with that. I have a system with 4 Watlow controllers, 3 are series 96 controllers, one is PID only and 2 are ramping. The 4th controller is an EZ zone. I am using RS485 for communications and the controllers are all wired in parallel for communications and power.
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This is the first I have ever worked with Modbus based communications. I have successfully programmed using the Modbus read/write VIs, and am wanting to move to shared variables. My questions right now revolve around addressing, Modbus I/O servers and COM ports. Specifically, at this point, I know the addresses need to match up between the server and the slave device (Watlow controller in my case), how many servers can I create and use on one COM port? If the number is limited, is there a way I can specify an address that I want the server to talk to? Will the broadcast mode work to request data values from the controllers?
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Hi all I am having a frustrating problem. I am trying to use shared
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Attachments:
PumpMonitoringDevice.zip ‏2083 KB

Adam:
You may be able to use arrays to speed up your program, but bear in mind that the TPC is pretty much guaranteed to be slower than your computer (as it's likely to have lower system specs).
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I am using Real time remote system. I am using PXI-6259 card, PXI-8184RT controller and PXI-1031 Chassis.
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Screen shot of this is available.
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Attachments:
SV2.jpg ‏2305 KB
SV3.jpg ‏2305 KB

You will have to give us the whole picture. What is your client computer; a PAC, desktop etc? What are you running on the client computer; a VI or an executable? Where are you going to deploy your library? On the host machine or the client machine?
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l_xml clob;
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Any idea ?
Thanks in advance
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Why are you using dynamic SQL statements? Why not just use something like this instead in your PL/SQL. I also replaced the leading // in your Xpath with just / since you start from the root node.
select *
INTO l_dummy
from xmltable(XMLNAMESPACES('http://www.w3.org/2001/XMLSchema' AS "XSD", default 'http://schemas.xmlsoap.org/wsdl/'),
                '/definitions/types/XSD:schema/XSD:element'
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select *
from xmltable(XMLNAMESPACES('http://www.w3.org/2001/XMLSchema' AS "XSD", default 'http://schemas.xmlsoap.org/wsdl/'),
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<xsd:schema targetNamespace="http://xmlns.oracle.com/orawsv/XFILES/F1" elementFormDefault="qualified">
<xsd:element name="SVARCHAR2-F1Input">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="A-VARCHAR2-IN" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
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<xsd:element name="RETURN" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
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</types>
<message name="F1InputMessage">
<part name="parameters" element="tns:SVARCHAR2-F1Input"/>
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<operation name="F1">
<input message="tns:F1InputMessage"/>
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</operation>
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I am creating an application where I have front panel indicators data bound to shared variables. I also set it up to have them blink when the alarm is on. I am using the DSC module.
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I have been using IE6 and Firefox, and I have found that the blinking does show up, if you refresh the page. And then if the alarm stops and the blinking stops, you will not notice it until you refresh again.
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Hi all,
I have a distributed application (PC + a few CompactRIOs). My PC contains variables that have aliasing enabled -- they are bound to variables on the cRIOs.
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I am having the same problem with Shared Variables with LV8.6.1 and Win7 64 in a program that uses a shared variables to share in seperate loops. I was able to use a local variable instead, but would love to know if it possible to use shared variables with 8.6.1 and win7.

Upgrade to 8.5.1 on all computers using shared variables?

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About the performance of using shared variables

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976208 wrote:
How to use v_date and m_id as bind variables in this procedure to avoid hard parsing.
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I have a curious coercion problem when using Shared Variables. I want to share the state of a State Machine, which is an enum saved as a control (typedef) called TYPE State (see attached). I create a shared variable called State and define it as a Custom Control, using the just-mentioned typedef. So far, so good. I've attached three simple VIs -- the first one, Init State, simply wires a constant to the input of the Shared Variable to initialize it -- the wired constant is, of course, defined by the typedef. However, the Get State and Set State, meant to wire an indicator (for reading the state) or control (for setting it), develop coercion dots when wired into the Shared Variable. Why? How do I get rid of the dot? [I suppose I could abandon my typedef and custom control, but the beauty of typedefs and custom controls is that it "enforces" rules, lets you use enums for clarity, keeps the code "honest", etc. -- I'd hate to give that up just to get rid of a dot!].
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Attachments:
Coercion Problem1.zip ‏38 KB

Hello Bob,
I am also seeing this behavior, I will escalate this question to our LabVIEW developers and post again here no later than next Tuesday, November 27th as National Instruments will be closed for the remainder of this week.
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Enjoy the holiday
Regards,
Erik J.
Applications Engineer
National Instruments

How to use shared variables with native c programs

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