Modbus - Ethernet IP configuration problem


#1

I have a 1976-1020-ND Ethernet/IP to Modbus converter. The E/IP side is connected to an ABB robot, the Modbus to a PLC. I can write data from the robot and receive that data in my PLC, but I cannot seem to write from the PLC to the robot. What might I be doing wrong?

Note: data read by the PLC starts at Modbus register one. ???


#2

Hello @ArtRabert,

Can you confirm this is an AV7669?

If i follow your description correctly it looks like you are able to read data from the robot just not write? It sounds like the issue might be with how you are doing the modbus requests. Depending on what modbus addressing mode the server is configured for you have different addresses and function codes available for reading and writing. Take a look at chapter 5 of the Ethernet interface. This section will describe both modes and provides a chart showing the modbus registers, the mapping to memory and the function codes. The mode itself is set though the Anybus Configuration Manager via the USB cable.

Let me know if you have any questions.

Regards,
Deryck


#4

It is a AV7669-F


#6

My mistake AB7669-F


#7

Thank it looks like i had a typo myself.

Did you verify if it is the modbus registers you are writing to that was causing the issues? Are you receiving any modbus error response back?

Deryck


#8

Modbus seems to read/write ok. I am using modbus poll to watch registers on that side of the network

Ip side I can write output registers but cannot read inputs


#9

Hello @ArtRabert,

It shounds like there could be an issue with the scan list. It is odd that you can write but not read data. How are you verifying that the writes are making it to the Ethernet/IP device? From the Ethernet/IP scanner webpage do you see any data from the monitor page?

What do you have configured in the scan list? Can you verify the connection points are correct? What are you using for originator > target ( output ) and Target to originator (input) instances and do they match what the target devices manufacturer states?

Deryck


#10

Hello Deryck,

Forgive my ignorance in all of this, here is what I know about the project in the field. I also created a connection diagram with some additional detail for the Anybus.

How are you verifying that the writes are making it to the Ethernet/IP device? I can input a numeric value in the Robot controller output register 1 byte wide. The data can then be read via programming software for the BRx (BX-ME) controller.

From the Ethernet/IP scanner webpage do you see any data from the monitor page? ??? I do not know about this….

What do you have configured in the scan list?
???

Can you verify the connection points are correct?
???

What are you using for originator > target ( output ) and Target to originator (input) instances and do they match what the target devices manufacturer states? ???

Kindest regards,

Arthur M. Rabert


#12

#14

Hi @ArtRabert,

No worried we should be able to get this sorted out. Here are some screen shots with some details. To start can you get a some screen shots showing your setup?

I think some scanner interfaces might be missing the monitor page. If yours does not have it you can access it from the modbus TCP web interface but it will be reverses, where the out and in are swapped. Meaning input on the modbus TCP side is the output on the Ethernet/IP scanner.

From the Ethernet/IP scanners webpage you can also setup the scan list:


Clicking on the target or add will give you this page.

This page will need to be configured to match the settings of your device the instances (originator to target & target to originator) should be able available from the OEM.


#15


#16

Good day Deryck

Well very possibly these scanner interfaces are missing. I cannot seem to ping them


#17

Do the devices show up in IP config? Can you try loading the webpage with Internet explorer?

Deryck


#18

I was successful late afternoon seeing web pages for both IP scanner and the modbus side of the gateway

I am noticing that my IP dose not want to seem and connect. The NS led is flashing green

I tried adding a target to the scan list but get an immediate error, MS light goes solid red


#19

From the Ethernet/IP network can you ping both devices? I would verify that the instances you are using match the ABB robot you are connecting to and the IO size matches. This is often the cause for the connections failing

Deryck


#21

Good day Deryck,

It had occurred to me that the write instruction coming from my PLC may be the issue. I had initially addressed both (read/write) instructions to communicate with the Anybus gateways from the modbus side, only using a single EIP address 192.168.1.45. I believe the ABB robot is 192.168.1.5. The robot required and EDS file which was set up to point to the ANybuss gate way at 192.168.1.45. If it is transmitting data to the gateway and passes through to the modbus side, is this the reason I have not seen data being written to the robot? My instruction leaving the PLC is currently set to write to the gateway and I can see it when online monitoring the data via the html portal

Kindest regards,

Arthur M. Rabert,

CEO & Industrial Technologist



#22

Hi Arthur,

Something might be getting over looked on the modbus side but im not sure i follow what you were asking. From section 5 of the Ethernet adapter User guide We explain the Modbus mapping to the ethernet interface. You will notice there is an input buffer and an output buffer that are accessed from different modbus addresses.
Are you saying you were only reading and writing to the same addresses? If you were you might not have been reading the data.

What are the NS and MS LED on the scanner doing? Are they both solid green?

Deryck