How to connect many cFP devices?

[Thang Nguyen]

Hi,

I start working on a project which requires connecting many cFP devices. The requirement is I have to put all of acqusition data in the modbus protocol, so the database of client can access to these data.

I have just thought about make each cFP work independentl with modbus server inside and run with deployed real-time program. Each cFP will have a range of data address shared variable. But I don't know that if all of these modbus servers can be combined to become one?

I woulk like to ask for your recommendations. This program does not need to be real time. Above is just one idea of mine. I am still thinking right now.

Highly appreciate your helps.

Best regards,

Thang Nguyen

[ned]

QUOTE(Thang Nguyen @ Sep 10 2007, 12:54 PM)

I have just thought about make each cFP work independentl with modbus server inside and run with deployed real-time program. Each cFP will have a range of data address shared variable. But I don't know that if all of these modbus servers can be combined to become one?

It would be easy to combine all the modules into one modbus server because FieldPoint IO items are treated identically regardless of whether they are local (directly connected to the network module) or remote. You could put all your shared variables, bound to a Modbus I/O server, on one of your Fieldpoint modules, and let that module retrieve data from all your other modules over your ethernet network. You'll only need code on one module, and all the other other modules can have "dumb" network interfaces (the cFP-1804/1808).

[Thang Nguyen]

QUOTE(ned @ Sep 10 2007, 01:40 PM)

It would be easy to combine all the modules into one modbus server because FieldPoint IO items are treated identically regardless of whether they are local (directly connected to the network module) or remote. You could put all your shared variables, bound to a Modbus I/O server, on one of your Fieldpoint modules, and let that module retrieve data from all your other modules over your ethernet network. You'll only need code on one module, and all the other other modules can have "dumb" network interfaces (the cFP-1804/1808).

Thanks for your recommendation.

[Thang Nguyen]

I tried to create a test project to test the modbus but it doesn't work. Could you help me?

In the target, I create a library. After that I create a Modbus Slave I/O Server. Then I create a shared variable bind to this modbus. In Target VI, I write the value to this shared variable. In the host VI, I read data from this VI. The issue is I only get value "1" from this shared variable with watever this shared variable is updated in the target.

I attach here all of the necessary images.

[ned]

QUOTE(Thang Nguyen @ Sep 12 2007, 01:33 PM)

I tried to create a test project to test the modbus but it doesn't work. Could you help me?

In the target, I create a library. After that I create a Modbus Slave I/O Server. Then I create a shared variable bind to this modbus. In Target VI, I write the value to this shared variable. In the host VI, I read data from this VI. The issue is I only get value "1" from this shared variable with watever this shared variable is updated in the target.

I attach here all of the necessary images.

Unfortunately I don't have access to a FieldPoint module to test this. I just switched jobs, and the last thing I did at the previous company was to set up Modbus communication over a serial link between a FieldPoint module and an autodialer - and it worked. However I was testing this using the configuration tool for the autodialer, which let me read the Modbus values directly.

This looks to me more like a shared-variable problem than a modbus problem, since you aren't verifying modbus communication. Have you checked for an error in the error-out clusters? Do you have the Shared Variable Engine and whatever else it needs installed on your FieldPoint module? It looks like you're hosting the StopFP1 variable on your computer; does that work? What happens if you instead host both variables on the FieldPoint module?