Labview timing issues with DAQ and Field Point

[NewMachine]

I am trying to acquire voltage signals from panel meters and at the same time send voltage signals out through field point. We are using RS485 connection. We can acquire data seperately and we can also send voltages signals through FP seperately, but it doesn't work in the same vi . It is setup in Labview within one while loop, using the FP express vi, and also using VISA serial read/write. Does anyone know why this won't work together? We get an error that the comm port is already in use etc. Thanks!

[Sean_C.]

Hello,

Are you using your FieldPoint bank on this 485 network? What hardware are you using for FieldPoint? If you attach your VI to this post, I waould be happy to take a look at it.

Sincerely,
Sean C.
Applications Engineer
National Instruments

[Aaron_G]

When you use the FieldPoint Express VIs, they call into and launch the FieldPoint Server. The FieldPoint Server is considered to own the serial port, and is considered a separate program from LabVIEW. Thus when you use VISA to talk to the other devices on the same serial port, VISA is unable to gain control of the port (only one program is allowed to own the serial port at a time). In order to use both the 3rd party devices and FieldPoint modules on the same serial port, you should use the FieldPoint Optomux VIs. These VIs are found under the FieldPoint>>Advanced>>Serial Configuration palette. Despite the label of "Serial Configuration" these VIs allow you to fully control the FieldPoint system, but require a greater level of programming than the Express VIs. These VIs are usually only installed by default on a system that has LabVIEW RT installed, so you may need to run a custom re-install of NI FieldPoint.

I recommend that you take a look at the following KnowledgeBase article to determine if the FieldPoint devices and your panel meters are fully compatible.
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/7771e92db978ed7d862568550079cd3a?OpenDocument

Regards,
Aaron

[NewMachine]

Thank you -- I have installed the RT examples.

Does the FP and 3rd party modules on the same 485 network need to be wired up in any particular way? We found that it wouldn't work in 2-wire "half-duplex" mode, and only in the "full-duplex" mode would it transmit/recieve at the same time. My panel meters don't support the fullduplex mode so if I use the FieldPoint Optomux can I have the modules and panel meters hooked up in two wire / halfduplex mode?

Thanks!

[Aaron_G]

Please refer to the KnowledgeBase article I listed in my last post for information on 2-Wire or 4-Wire compatibility. The article provides examples and information on the constraints that may be imposed. Without knowing the protocol used by your panel meters, I can not provide an answer to your question.

Regards,
Aaron

[NewMachine]

I read the knowledge base link and it says that FP supports 2-wire mode, but what I don't know is if two types of equipment can be on the same 485 network doing different things in 2-wire mode? It didn't work for me but it could be an "operator error". My Newport i32 panel meters are 2-wire mode config only. Field Point 1001 module supports 2-wire mode, but to what extent? Thanks....

[rolfk]

NewMachine wrote:
> I read the knowledge base link and it says that FP supports 2-wire mode,
> but what I don't know is if two types of equipment can be on the same 485
> network doing different things in 2-wire mode? It didn't work for me but
> it could be an "operator error". My Newport i32 panel meters are 2-wire
> mode config only. Field Point 1001 module supports 2-wire mode, but to
> what extent?

Fieldpoint has most probably a different communication protocol than the
Newport device. Mixing different protocols on the same bus is most times
a NoNo.

For adressing multiple devices with the same protocol you have to make
sure only one of them acts as master (usuallu the PC) and each of them
uses a different network address.

Rolf Kalbermatter

[NewMachine]

Thanks! I just needed some kind of explanation like this so I can move on. 🙂