ASCII over Ethernet from L24ER

godcixelsyd

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Join Date
Jan 2013
Location
Georgia
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102
Hello wise PLC sages! I'm on an attempted quest for knowledge, and think I'm getting close to a resolution or discovery that I've been wasting my time. So, the story so far... I have a ViewMarq LED display from Automation Direct. I would LIKE to control it over Ethernet without purchasing a COMMS gateway to go between my PLC and it. I have found documentation on Ethernet/IP Socket Interface and have gotten that working (as best I can tell).

I have a message to create the socket that I'm receiving a .dn bit when I flag it, and I'm getting an instance written to the output tag.

From here I use that instance for a message that opens the connection, creating it for the target IP address and port (my string here is "192.168.1.105?port=502" in my example), which gives me the proper .dn bit so I believe this is working as well?

Finally I do a SocketWrite with the ASCII string I need to use being COPied into the outgoing Buffer. Here I will usually get a .dn bit if it's a newly opened socket and hasn't timed out (a problem I'm fine with facing once the once I'm controlling the screen properly), but am not seeing any kind of change on the LED screen based on the command I'm sending it.

So... Any thoughts or questions that may get me the last few steps?
 
Use pre-built AOI from the Knowledgebase - no need to write your code.

Usually Port 502 is for Modbus/TCP - there is a pre-built application for it.
 
Use pre-built AOI from the Knowledgebase - no need to write your code.

Usually Port 502 is for Modbus/TCP - there is a pre-built application for it.

Thanks, I actually found one and it's part of why I've gotten where I am. It's got more features than I really need so I kinda "picked it apart". I don't have a spare controller to put the program into for testing, and am using a live PLC on the network (not controlling a critical process, but shouldn't take it down for this). I'm thinking maybe I'm having a formatting issue? The help file for the screen doesn't specifically call out being able to do this over ethernet for Allen Bradley PLCs, and gives the guide for doing it via serial. It does however have a guide for other PLCs over ethernet, so if I can get the format coming from the PLC correct it should theoretically work. I've read about capturing network traffic to analyze it, but haven't done it. I'm thinking that may be my next step, to verify the string being ouput looks correct. Off to research!
 
Use pre-built AOI from the Knowledgebase - no need to write your code.

Usually Port 502 is for Modbus/TCP - there is a pre-built application for it.

Ok, I found a different one than I found the first search (kbase topic 89798), and it was more straight forward on how to import it into the existing logic. On top of that it had UID in the parameters to set, which the instructions called out as something that needed to be set for proper operation when using a different brand of PLC. It looks like everything is right in the world, thanks for your help Contr_Conn!
 
If you want to write your own and looking for a basic commands then you should use TN 32962. It's very old but gives you basic tools, correct MSG configurations and pre-defined data structures.
 
If you want to write your own and looking for a basic commands then you should use TN 32962. It's very old but gives you basic tools, correct MSG configurations and pre-defined data structures.

Contr_Conn, I'm running into an issue with my addressing, and since you've had some experience with this... have you dealt with slave devices where the modbus mapping used values higher than normal? For example, my 40000 registers are actually 400000 registers. So where I need to access is in register 411000, but when I try putting 11000 in my begin address it gives me an illegal data address error. The bit I've read on it boils down to some masters can't access certain slave addresses. Have you experienced anything simmilar?
 
I am not very familiar with Modbus Master code, I wrote only the initial Modbus Slave code that was modified slightly later.

Without looking at the code, I would guess there is a check in the code (probabaly 0-9999) that you may have to defeat.
This is just a guess.
Modbus should support 4xxxxx addresses where xxxxx is 0-65355
If code uses INT that it may limit it to 0-32767.
This is all that I recall.
 
Did you ever get this working?

I'm in the same boat with a ViewMarq. Downloaded the sample code but I'm lost. I'm trying to integrate this into an advanced PLC class I teach but I'm lost.
 

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