Help
  • Explore Community
  • Get Started
  • Ask the Community
  • How-To & Best Practices
  • Contact Support
Notifications
Login / Register
Community
Community
Notifications
close
  • Forums
  • Knowledge Center
  • Events & Webinars
  • Ideas
  • Blogs
Help
Help
  • Explore Community
  • Get Started
  • Ask the Community
  • How-To & Best Practices
  • Contact Support
Login / Register
Sustainability
Sustainability

Join our "Ask Me About" community webinar on May 20th at 9 AM CET and 5 PM CET to explore cybersecurity and monitoring for Data Center and edge IT. Learn about market trends, cutting-edge technologies, and best practices from industry experts.
Register and secure your Critical IT infrastructure

Modbus RTU RS485 Fault finding with Transmit and Receive LEDs

Building Automation Knowledge Base

Schneider Electric Building Automation Knowledge Base is a self-service resource to answer all your questions about EcoStruxure Building suite, Andover Continuum, Satchwell, TAC…

cancel
Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for 
Show  only  | Search instead for 
Did you mean: 
  • Home
  • Schneider Electric Community
  • Knowledge Center
  • Building Automation Knowledge Base
  • Modbus RTU RS485 Fault finding with Transmit and Receive LEDs
Options
  • Bookmark
  • Subscribe
  • Email to a Friend
  • Printer Friendly Page
  • Report Inappropriate Content
Invite a Co-worker
Send a co-worker an invite to the portal.Just enter their email address and we'll connect them to register. After joining, they will belong to the same company.
You have entered an invalid email address. Please re-enter the email address.
This co-worker has already been invited to the Exchange portal. Please invite another co-worker.
Please enter email address
Send Invite Cancel
Invitation Sent
Your invitation was sent.Thanks for sharing Exchange with your co-worker.
Send New Invite Close

Related Forums

  • Intelligent Devices Forum

Previous Next
Contributors
  • DavidChild
    DavidChild
  • Dave_Shore
    Dave_Shore
  • Jonathan
    Jonathan
  • Product_Support
    Product_Support

Invite a Colleague

Found this content useful? Share it with a Colleague!

Invite a Colleague Invite
Back to Building Automation Knowledge Base
Options
  • Bookmark
  • Subscribe
  • Email to a Friend
  • Printer Friendly Page
  • Report Inappropriate Content
0 Likes
4256 Views

Link copied. Please paste this link to share this article on your social media post.

Trying to translate this page to your language?
Select your language from the translate dropdown in the upper right. arrow
Translate to: English
  • (Français) French
  • (Deutsche) German
  • (Italiano) Italian
  • (Português) Portuguese
  • (Русский) Russian
  • (Español) Spanish

Modbus RTU RS485 Fault finding with Transmit and Receive LEDs

Picard Product_Support
‎2018-09-06 01:07 PM

Issue

Using the RD and TD LEDs to help commission and Fault finding a Modbus RTU Continuum Xdriver

Using the RX and TX LEDs to help commission and Fault finding a Modbus RTU AS, AS-P, AS-B

Product Line

  • Building Operation Automation Server Premium
  • Continuum bCX4040 (BACnet)

Environment

  • Continuum
  • Automation server

Cause

How to use the TD RD(TX RX) LEDs to help commission or check an installation

Resolution

Continuum
The Comm Port LEDs on a net controller can be helpful when first setting up or fault finding an Xdriver (ModbusRTU)
Every time the net controller transmits the TD LED will flash and every time another device on the bus transmits (such that the net controller can receive it) the RD LED will flash.
Thus if Xdriver seems not to be working correctly this is often the first thing to check
A simple check with Modbus RTU would be to stop any automatic polling on the network, then manually refresh a modbus point and watch for a single Transmit (TD) followed by a Receive (RD).

SmartStruxure
The Comm Port LEDs on an AS controller can be helpful when first setting up or fault finding ModbusRTU
Every time the AS transmits the TX LED will flash and every time another device on the bus transmits (such that the AS can receive it) the RX LED will flash.
A simple check with Modbus RTU is to create only a  single device (or inhibit polling to all but one device) and watch for a single Transmit (TX) followed by a Receive (RX).

Modbus Simulation
Another useful technique when commissioning or troubleshooting with Modbus is to simulation software on a PC (with RS232/485 convertor for RTU if required).
A Slave device or the Master node can be simulated
eg ModSim, ModScan, ModbusSlave, ModbusPoll, Mod_RSsim

Labels (2)
Labels:
  • Andover Continuum
  • EcoStruxure Building Operation
Tags (16)
  • Find more articles tagged with:
  • 6511
  • as-b
  • as-p
  • bcx
  • DavidShore19
  • light
  • modbus rtu
  • ModbusRTU
  • nc
  • nc1
  • nc2
  • netcontroller
  • rs232485
  • X Driver
  • x-driver
  • xdriver
Was this article helpful? Yes No
0% helpful (0/1)

Link copied. Please paste this link to share this article on your social media post.

To The Top!

Forums

  • APC UPS Data Center Backup Solutions
  • EcoStruxure IT
  • EcoStruxure Geo SCADA Expert
  • Metering & Power Quality
  • Schneider Electric Wiser

Knowledge Center

Events & webinars

Ideas

Blogs

Get Started

  • Ask the Community
  • Community Guidelines
  • Community User Guide
  • How-To & Best Practice
  • Experts Leaderboard
  • Contact Support
Brand-Logo
Subscribing is a smart move!
You can subscribe to this board after you log in or create your free account.
Forum-Icon

Create your free account or log in to subscribe to the board - and gain access to more than 10,000+ support articles along with insights from experts and peers.

Register today for FREE

Register Now

Already have an account? Login

Terms & Conditions Privacy Notice Change your Cookie Settings © 2025 Schneider Electric

This is a heading

With achievable small steps, users progress and continually feel satisfaction in task accomplishment.

Usetiful Onboarding Checklist remembers the progress of every user, allowing them to take bite-sized journeys and continue where they left.

of