Modbus Poll
Olegario Benford
Modbus Poll is a Modbus master simulator designed primarily to help developers of Modbus slave devices or others that want to test and simulate the Modbus protocol. With the multiple document interface you can monitor several Modbus slaves and/or data areas at the same time. For each window you simply specify the Modbus slave ID, function, address, size and poll rate. You can read and write registers and coils from any window. If you want to change a single register, simply double click the value. Or you can change multiple registers/coils. Multiple data formats such as float, double and long with word order swapping are available.
I am trying to do the exact same thing that I do in Modbus Poll in labview to get a connection with a modbus device. There are different connection setup data to be selected. I have attached the a pic of the modbus poll connection setup.
One of the content here as you can see is the delay between polls. But in LabVIEW while making a modbus connection, I cannot find that option. All the other stuff such as type of connection, serial settings like baudrate, data bits, parity, stop bit and timoeout can be found in labview but not delay between polls. Can anyone help me find out how I can set that data. Thank you.
Like the comments before, you are the one making the requests (the polls), if you need to make continuous reads you would need a loop (for or while, it depends what is the task you are trying to solve) and a timer between each iteration (this would be your Delay between polls), but if you want a similar configuration panel for the user of the software you are writing, you need to provide the control used as input to your timer.
I have a system with 4 modbus addressed registers: MBA: 1, 13, 15, 17. When I connect modbus poll to the chain, I can successfully poll all the data on three of the addresses. When I try and poll the registers on address 1 I get an error and can't read those registers, we added 3 new registers to the data, 42, 43, 44. The weird thing is when I connect the cable back up to the PLC I can read the data on the MBA: 1, except for the three new registers added. What's up?
Edit: a little clarification, the four devices are on four different Slave IDs, 1, 13, 15, and 17. All the data from slave IDs 13, 15, and 17 are good and we can read all the registers. For Slave ID 1, we are getting error illegal data address. When we poll a single register on the device on Slave ID 1, that we know 100% has data coming through, it gets the illegal data address error.
only my opinion, if your info about 2 PLCs connected together was functional, I see problem probably in MB poll SW or Moxa adapter. I must say, I had one of this adapters (older type one) and was not satisfied with it's functionality, next Moxa adapters/converters (like NPort) are ok in my opinion, but this can be personal opinion. I don't know that MB poll SW functionality, so don't know if someone will answer exactly what problem can be, maybe with parameter of requested address of register (some SWs use offset/ some not), maybe also max amount requested data (also must be checked in your DB if are sufficient). Hope you'll find problem so soon, good luck.
I'm curious how you did that test with app from SimplyModbus. Simply if you send some request from PLC to Slave PC app (f.ex. simplymodbus RTU Slave), you must see in app error message or something depended to request. If you can, make again one test and post screenshot from Slave RTU app simply modbus, not that other SW (I don't know it's functionality). Look carefully to TX/RX lights of your CM module and also to Moxa's LEDs. You can also omit these MB SWs and connect simple Hyperterminal and after recv check incoming message consistency (also you can attach screenshot with of course description what you request from PLC - can be quickly checked). Simply you must try more options, no other way.
look to www.simplymodbus.ca for byte sequence description, also you have that in SW. Look, logically 20 bytes are only your needed 10 values but MB complete message must also include other needed informations that are described in help. Pay attention to not manipulate with standard settings in PC SW (offsets) if you don't know really what you do. This can be not easy then recreate back to functional state.
hi guys. i have a question. i tried communicate to modbus with enc28j60 module but o can't do it. i use the ModbusIP_ENC28J60.h library and simple examples. but i didn't connect to modbus? please help.
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i use arduino nano with nano ethernet shield v1.0. nano ethernet shield has enc28j60. so it's different wiznet 5100 but i find library and connect network and webserver but if i tried communicate with modbus protocol it connect to program (modbus poll) read once then give read error issue. it's not to much code and i get it but i did not how to figure read error issue. please help . thank you all.
hii guys i have one question.i searched that issue and i found that "library send one packet that is the reason modbus poll read once then connection lost" .how can i send multi packets to enc28j60. i use ModbusIP_ENC28J60.h library. or am i wrong ? please help. thank you all.
If the assumption is correct then possibly the packets you are sending are not fully supported by our routing functions, our devices support routing for some modbus functions but not all of them. We mainly support the Modbus commands such as read & write registers used by Temco products, that is Modbus functions 03, 06, and 16.
But. Because the result was not as expected, I hooked an old T3-8I13O and tried to add it automatically (scan) to see if the network scan worked.
The automatic scan was a failure (not detected, serial or main/sub). But was succesful if I added it manualy (add serial modbus device), including the integrated modbus poll from T3000 (latest version).
In my case, T3 unit = 107, the rs485 sub modbus device ID = 40 and the 2 int16 addresses I want to poll are 35 & 36 and transform those 2 integers into 1 float
what should be the programming line ?
However, after few minutes, spontaneously, the setting of the sub network of my T3-LB, while polling, is going from master to slave and the poll stops.Firmware 54.4 and latest T3000
Any idea ?
Update: switched modbus networks: set sub rs485 as unused and set main rs485 as master and will see how it behaves. feedback on this later.
Nope, test finished: same problem, the rs485 switches always from master to slave and stops communication with my 3rd party device.
If not, then duplicate the modbus node and make a big long line of the function, then modbus, then next function, then next modbus and so on, in each function after the modbus, move the msg.payload to a new msg property so out the end of the chain you will have all your msg.stuffIwant in its own message.
Of course each function node also as the code in your current function nodes, just add that one line of moving the result of the modbus call into a different msg so it does not get over written by the next call.
With Modbus Poll (64-Bit) you can monitor and test your modbus slave devices. It supports RTU and ASCII mode, it tests Center for modbus slave developers, it has multiple windows for monitoring of multiple slaves or data areas and Monitoring of serial traffic. Data logging to a text file readable by MS Excel.
Modbus Poll (64-Bit) is a Modbus simulator designed primarily to help developers of Modbus slave devices or others that want to test and simulate the Modbus protocol. With the multiple document interfaces you can monitor several Modbus slaves and/or data areas at the same time. For each window you simply specify the Modbus slave ID, function, address, size and poll rate. You can read and write registers and coils from any window. If you want to change a single register, simply double click the value. Or you can change multiple registers or coils. Multiple data formats such as float, double and long with word order swapping are available. In Modbus Poll exception errors are shown on the status line.
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