Universal Robots Forum

Connect and work with external IO (via Modbus)

Good morning together,

I´m connected 2 “Moxa” modules via Modbus to the Robot.
When i go to the Roboter-panel-> EA-> external i can see now the signals.
Unfortunally i couldn´t find, what do colors of the circles infront of each Input/Output mean?
Sometimes they are green/ yellow falshing, some of them are yellow, some are grey…

Does anyone know, what the colors mean? also some of the outputs are kind of invisible/grey… and i cannot click on them.
I´m thankful for any kind of help.

Kind regards

Explanation is slightly scattered in user manual “MODBUS Client I/O Setup” section.
Yellow means that responses from PLC are coming back too late. Frequency can be set in fieldbus installation section in advanced signal options.
Gray means that there is no response from PLC.

Hallo mmi,

I got 3 additional questions:

  1. How do I know which frequency i have to select?

  2. I have some Outputs that i cannot operate. I click on the output, but on the Robot-panel nothing is shown.
    BUT if i check on the valve (or online via webbrowser on the Moxa module) i can see that the output is on.
    Tbh I don´t know if the Problem is on the Roboter setup side or on the Moxa setup side.

  3. I can see online at the webbrowser, that some Inputs are True, but those inputs are shown False on the Robot Panel.
    also here I don´t know what to do.

I´m very thankful for any kind of support.

Kind regards

I’d start from looking at outputs/inputs that are actually working. If some of them are working, and some not, then it’s probably PLC program that is not configuring them correctly. There is no error code on “gray” outputs - that means that robot did not get any response from PLC.

Answering questions:

  1. It depends. Default value is 10Hz.In your case there is not that many signals configured, so should be low enough. You can try lowering it to 5 or 2Hz for less critical signals.

  2. If output is not connected, then value can not be changed

  3. I can not explain it. Make sure that you’re using correct output types (bits, coils, registers) on the PLC side. There are distinct address spaces in modbus specification. UR supports only limited subset of modbus commands. Documentation is clear about supported commands. You can also search forum for similar topics.

good morning mmi,

thank you for your feedback.

I think I found the issue with the signals that are “slight” grey.
For those outputs I used special letters like “ä” or “ü”…
Once I have removed those letters it was working fine.

I´ve set the frequence now to 5Hz and all IO are green.