Troubleshooting : BACNet Communication Networks

BACNet

BACNet is an easier communication protocol to troubleshoot due to the ability to discover devices rather than manually adding (like modbus) and the additional information displayed when using certain discovery tools (specifically Tridium devices). In addition to overall troubleshooting, listed below are specific items to troubleshoot when dealing with either IP or MSTP.

• Step 1 : Do you have all relevant information for this project / site / instance?
  • This includes CDDs, model numbers of devices on the trunk, wiring details for all communication terminations, and manufacturer manuals specifically for communication protocol details.
• Step 2 : Have the Installer confirm that all wiring terminations have been met per our CDDs and Wiring Details.
  
  • Also confirm at this point that all end devices have been configured properly (Baud Rate, Address, Device ID, Communication Protocol)
• Step 3 : If confirmed affirmatively, then break up the trunk so that only 1 device is connected to our integration controller (either DP or JACE).
  • This allows us to narrow down the issue to either a faulty trunk, faulty terminations, or conflicting addressing.
• Step 4 : If you have been unable to solve it with Step 3, then have the installer cycle power to both the end device and the Integration Controller (regardless if this has been done earlier).
  • Believe it or not, this can solve issues just like any other IT issue.
• Step 5 : After the power cycles, attempt another discovery. If it fails, then have the installer check continuity on the wires going from our Integration Controller to the end device.
  • Checking for continuity confirms if there are breaks, faults, or loose wires in the communication cable, which can be a root cause of Integration failure.
  • If the installer finds that there is not continuity on the cable, then it will need to be ran again, properly this time.
• Step 6 : If still unsolved at this point, have the installer swap out the end device with another BACNet controller that you know for a fact will work (Hyperstat reconfigured as a BACNet Stat is a solid option).
  • Once the new device has been tied to the integration controller, try another discovery. If you are able to discover the new end device, then that means there is an issue with the original end device you were trying to integrate. This means replacement or warranty will be required.
  • If you do cannot discover the new end device, move ahead to the next step.
• Step 7 : Using YABE, have the installer attempt to discover the BACnet Device using a local YABE instance (follow instructions here).
  • If the installer is able to discover the end device using YABE, then that means either the Integration Controller is not configured properly, faulty, or has a faulty comm termination block.
  • Step 7A : Confirm that the integration controller is configured properly. If it was not configured properly, reconfigure and restart from step 3.
  • Step 7B : If Step 7A Did not work, then have the installer swap the communication cable from the original comm port to a new one, and restart from step 3.
    • This identifies that a Bad Communication port was the issue, if it resolves the communication issues.
• Step 8 : If the issues are still unsolved, then something was not performed properly, either these troubleshooting steps, configuration of the Integration Controller, or configuration of the end device.
  
  • My recommendation at this point, would be to revert everything to defaults (not factory reset, just default settings) for the integration controller, and then have the end device have all communication settings reset and reconfigured.
  • If this does not solve it, then reach out to Joe P or Jacob K. Be sure to have a list of all troubleshooting attempted to easily and quickly debrief them.

BACNet MSTP Nuances

• If troubleshooting a very large network, start by breaking it in half. If the issue persists, then cut in half again. If at any point when you cut the trunk in half the issue is resolved, it is in the half or quarter that you just removed.
• Always be sure to check device ids and mac addresses to ensure that all devices are unique. Having a duplicate device ID will cause an egregious amount of issues.
• Sometimes the simple things are the problems; bad connection on communication terminals, bad communication port, power cycle, swapped polarity. The mindset when troubleshooting should always be simplest solution first, then work upwards in complexity.

BACNet IP Nuances

• Device IDs on BACNet IP Networks are even more dangerous than with MSTP. To ensure that your device ID is unique, be sure to use a unique modeler to create the device id.
  • My rule of thumb is : take the last three octets, then add 01.
• If you are having issues discovering the device, make sure that it is using the correct UDP Port (47808 is typical).