Override BACnet Input Objects

By Matt

Have you ever had an outside air temperature sensor fail, causing a building’s automation to go nuts? Instead of overriding the entire building, why not just override the sensor? Usually with building automation systems you have to explicitly program this functionality. This is an area where BACnet shines: the protocol was designed by ASHRAE with…

BACnet Object Types

By Matt

The BACnet standard supports at least 18 different BACnet objects. ASHRAE will add new object types from time to time, but it’s rare to see these exotic object types in the field. The common objects provide intuitive access to building automation features. There is a loop object for PID loops, a calendar object for holidays…

MS/TP Capture Tool now Included with Wireshark!

By Matt

Wireshark is a fantastic tool for network diagnostics. It’s been the best tool for BACnet/IP network troubleshooting for years. It’s even been able to dissect MS/TP traffic dumps if you knew how and had the right tools. Well, those tools come standard now! Check out the new Wireshark BACnet MS/TP capture tool, included in 2.4.4…

What Is BACnet?

By Matt

The Basics – What is BACnet? BACnet is a popular building automation protocol used worldwide to enable communication between devices in commercial automation systems. Industrial automation has historically used other protocols such as OPC and Modbus. BACnet standardizes communication across vendors and simplifies the integration process. The name BACnet stands for building automation and control…

Overview of Commercial Automation Protocols

By Matt

In automation there are several communication protocols. Some are entirely proprietary and others are open. Despite the friendliness of the word, “open” isn’t always good news. Some of the older proprietary protocols are easy to integrate with off the shelf integration products. Two versions of the same protocol often look different. It’s a zoo out…

Add a Remote Device Without a BBMD

By Matt

You may encounter a situation where you must add a device on a different network. You may have no control of the BBMD configuration or you may have no BBMDs available due to poor device support. In these situations, you may have to add a remote device without a BBMD. It’s a handy trick, but…

When and Why Do We Need an End of Line Termination?

By Matt

End of Line Termination Concept Most of the buses we use are specified with end of line termination in mind. In the field these terminations are not always present, especially in short runs. Do we need them? Here’s an analogy I like that illustrates why we need end of line terminations: a bus behaves like…

RS-422 – The Other Bus-meat

By Matt

I encountered an RS-422 bus for the first time recently and it threw me through a bit of a loop! The device was a Modbus/RTU slave device and so I anticipated a RS-485 connection as per usual, but that was not the case. It’s the same cable, and the same essential signalling standard, but if…

RS-485 Bus Details

By Matt

Low-voltage communication buses are critical to networked automation systems and when they fail they are a pain to troubleshoot. We use them because the cables are cheap and you don’t need expensive switches, but what you save in parts you may pay in labor later. Ethernet/IP based communication is on the rise, but is still…

IP-based Protocols and Building Automation Security

By Matt

When installers build automation systems getting it working is their main focus. They see building automation security as an obstacle to overcome rather than the goal. If authentication is getting in the way, they disable it. When firewalls are blocking communication, they disable that too. Even more problematic is the fact that several popular automation…