Demystifying Modbus Function Codes

Posted by Kevin Rutherford on Dec 13, 2018 2:00:00 PM

With the wide range of devices that use Modbus for their communication protocol, you'll find many different interpretations, terminology and labels with respect to how to access different types of data in those devices.  Sometimes a device manual might only refer to the supported Modbus function codes and the range of offsets available for those function codes.

In this blog post, I will step through the specifics of Modbus function codes and how they pertain to addressing, and how they affect what addresses to use in TOP Server for Wonderware applications.

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Topics: Wonderware, TOP Server, Modbus, Automation 101, Protocols

Did You Know? How to Recover from Device Errors with OmniServer Error Messages

Posted by Kevin Rutherford on Nov 7, 2018 2:00:00 PM

With any communication server for collecting process data, there has to be a reliable mechanism built-in for dealing with error responses from the underlying devices.  This is true even for OmniServer as a user-configurable communication server.

Continuing our "OmniServer Did You Know?" blog series, this blog post focuses on how to use error messages and notification items in an OmniServer protocol to properly handle error responses or conditions received from your non-standard process devices.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, OmniServer Did You Know, error handling

Demystifying Modbus Register Addressing with TOP Server for Wonderware

Posted by Kevin Rutherford on Oct 11, 2018 2:00:00 PM

I'm sure you've all at least had some interaction with Modbus, working in the automation industry.  It's one of the most widely used protocols (if not the most widely used) in the world.  Which is both its blessing and its curse, to some extent.

Given how long Modbus has been around and in use as an "open" protocol (starting in 1979), there have been many different interpretations of Modbus throughout the years.  And with those different Modbus interpretations, much confusion about the different terminology for accessing data.

In this blog post, I will step through the basics of Modbus addressing including how offsets come into play, and how they affect what addresses to use in TOP Server for Wonderware applications.

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Topics: Wonderware, TOP Server, Modbus, Automation 101, Protocols

Did You Know? How to Setup Chained Messages in OmniServer

Posted by Kevin Rutherford on Oct 4, 2018 2:00:00 PM

In a nutshell, OmniServer's purpose is to retrieve information from devices that use ‘non-standard’ protocols to communicate such as weight scales, barcode readers, and printers.

Sometimes with some protocols, simply sending one message to a device, or doing nothing but simply transferring data to a client isn't enough. There are some more complex protocols where you will need to send a series of messages to the instrument, or respond to an event coming in from the device or to handle a sequence of handshaking messages. This is where "chained messages" come into play in an OmniServer protocol.

In this second post of a follow-up to our "OmniServer Did You Know?" blog series, we will cover how to chain multiple OmniServer command/request messages together in a protocol to flexibly handle such complex protocols.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, OmniServer Did You Know

Did You Know? How to Setup a Heartbeat Message in OmniServer

Posted by Kevin Rutherford on Sep 20, 2018 2:00:00 PM

As you probably know, OmniServer is used to retrieve information from devices that use ‘non-standard’ protocols to communicate such as weight scales, barcode readers, and printers.

In some situations, device protocols need to be designed to where the client application (HMI, SCADA or other), and not OmniServer, is in complete control of the polling. But before you send out the next message, how do you know if the device is still connected?

In this first post of a follow-up to our "OmniServer Did You Know?" blog series, we will cover how to create what is known as a heartbeat message to confirm your device is "listening" before sending the next message.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, OmniServer Did You Know

Building Custom CRCs for Non-Standard Protocols

Posted by Kevin Rutherford on May 17, 2018 2:00:00 PM

If you’ve been following our blog series on custom error detection, you’ll remember that OmniServer provides a large number of pre-defined Error Detection Codes (EDC) for use in different protocols for non-standard device communication.  And, again, it’s not uncommon to find an EDC from a vendor that is not pre-defined due to some specialized handling by the device manufacturer.

As we covered in our previous posts on creating a custom checksum and LRC, OmniServer gives you the ability to build custom EDCs in an OmniServer protocol to handle these situations.  This post, the final of three on custom Error Detection Codes, covers the basics steps to creating a custom CRC (Cyclic Redundancy Check) in an OmniServer protocol.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, drivers, connectivity, OPC, OPC DA, OPC UA, Protocol Design, Error Detection, CRC

Building Custom LRCs for Non-Standard Protocols

Posted by Kevin Rutherford on Apr 19, 2018 2:00:00 PM

You may be aware that OmniServer provides a wide variety of pre-defined Error Detection Codes (EDC, also known as CRC, LRC and Checksums) for use in protocols for non-standard device communication.  However, it’s not uncommon to find an EDC that isn’t pre-defined due to some specialized handling by the device manufacturer.

To handle such situations, OmniServer provides the ability to build your own custom EDCs in an OmniServer protocol.  This post, the second of three on custom Error Detection Codes, will cover the basics of creating a custom LRC (Longitudinal Redundancy Check) in OmniServer.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, drivers, connectivity, OPC, OPC DA, OPC UA, Protocol Design, Error Detection, LRC

Building Error Detection Codes for Custom Protocols

Posted by Kevin Rutherford on Mar 15, 2018 2:00:00 PM

If you’ve worked with OmniServer to connect your non-standard devices in the past, you may be aware of the large number of pre-defined Error Detection Codes (EDC, also known as CRC, LRC and Checksums) available.  However, as is the nature of custom protocols out there, it’s not uncommon to find an EDC that isn’t pre-defined due to some specialized handling by the device manufacturer.

To that end, OmniServer provides the flexibility to define your own custom EDCs in an OmniServer protocol.  This post, the first of three on custom Error Detection Codes, will cover the basics of creating a simple custom checksum in OmniServer.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, drivers, connectivity, OPC, OPC DA, OPC UA, Protocol Design, Error Detection

Did You Know? Four Key OmniServer Tips For Easier Protocol Creation

Posted by Kevin Rutherford on Feb 8, 2018 2:00:00 PM

As someone who has worked with non-standard device connectivity using OmniServer for over 10 years, I sometimes take for granted the knowledge that I have gained over that time.  If you're anything like me, once you figure out the data you need from your device's protocol document, you just want to get your protocol knocked out as quickly as possible so you can start communicating.

In this post, I'm going to cover 4 key tips that I've learned over the years when working in OmniServer to build a protocol that you may not have realized and that could add convenience and save you a lot of time, which is time you can be spending on other important tasks.

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Topics: Wonderware, Device Integration, OmniServer, Protocols, OPC Server, connectivity, drivers, OmniServer Did You Know

How to Connect a Non-Standard Device with No Code

Posted by Kevin Rutherford on Jan 4, 2018 2:00:00 PM

l ask you to remember back to our blog post last month where took the information we pulled from a device’s protocol document (in the prior month's blog) and created a custom protocol in OmniServer.  As you’ll recall, our protocol has now been designed.

But how do you go about testing the protocol and proving that it works? This final post in the series takes you through the steps of getting connected and actually troubleshooting your OmniServer protocol.

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Topics: Wonderware, Device Integration, Protocols, OmniServer, drivers, connectivity, OPC, OPC DA, OPC UA, Protocol Design

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