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Modbus TCP Client

Created by: GLouw at: 10/7/2014 3:39 PM (12 Replies)

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10/7/2014 3:39 PM	Rate (0)
GLouw Posts: 5 Rating: (1)	Hi all, I want to communicate to a SMA 6.0H Inverter using Modbus TCP to read my battery charge status. I have looked at examples and at the S7-1200 system manual. I get error 16#8384 - Data value error. I have downloaded a small modbus poll application and can read values that I am looking for. Please see attached a screenshot at my program. In the SMA Modbus table it is stated that the address I want to read is 30847 - Battery capacity - 2 Words - 0xFFFF FFFF Hope someone can help me. Regards Gerhard Attachment Modbus TCP.JPG (1927 Downloads)
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10/7/2014 5:35 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (323)	Hello Gerhard, error 8384 means that the server answers with exception code 3. In your post you wrote you are going to readinput register 30847, in the screenshot you have parameterizedholdingregister 40847. Probably that is what the server is concerned about. Regards, Kaulquappe
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10/7/2014 5:49 PM	Rate (0)
GLouw Posts: 5 Rating: (1)	Thanks Kaulquappe, That was just by playing around with the addressing. I have tried it with 30847. I have also connected two S7-1200 using Modbus TCP successfully so I really do not know what I am doing wrong here. Regards
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10/7/2014 7:06 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (323)	Hello Gerhard, well, I think you should ask the support of the 3rd party device when exception 3 is sent. Regards, Kaulquappe
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10/11/2014 12:07 PM	Rate (0)
GLouw Posts: 5 Rating: (1)	Thanks Kaulquappe, They are not able to help me. I am a bit condused by the addressing. Please see attached foto. Is the address 30845 in the extended address range of the modbus spesifiaction? So I need to enter 330845 in my MB_DATA_ADDR? I understand that the S7-1200 does not support extended addressing. Regards Gerhard Attachment SMA Modbus table 1.JPG (1447 Downloads)
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10/13/2014 10:30 AM	Rate (0)
Kaulquappe Posts: 3093 Rating: (323)	Hello Gerhard, due to the screenshot I would use MB_DATA_ADDR = 30845 MB_DATA_LEN = 2 Regards, Kaulquappe
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10/15/2014 4:02 PM	Rate (0)
GLouw Posts: 5 Rating: (1)	Thanks Kaulquappe, I have been spending days on this problem and even upgraded to V13 and using V3.1 of the MB_CLIENT. What is the difference in the Connect ID and MB_Unit_ID? (Static tag of MB_Client instance data block) On the Modbus server settings the unit is defined as Unit ID 3. Must this ID be used in the Connect ID or MB_Unit_ID? When writing 3 to MB_Unit_ID my error changes from 8384 to 8383 (Error in the data address or access outside the address area of MD_DATA_PTR.) Looking at the first screenshot in my post is am writing to an array of words. I have tried DWORD, INT, UINT, DINT with no success. I can however read the values on the modbus server with computer applications (Modbus Poll, Modsak and with a program in visual studio) Any ideas? Thanks. Gerhard
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10/15/2014 6:54 PM

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Kaulquappe

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Hello Gerhard,
the Connect ID is a logical number used by the CPU to specify a connection. The CPU has got several instances, one for each connect ID. This instance contains IP-address, port number, protocol and so on. This number is not sent on the line.

The MB_Unit_ID is a byte in the Modbus frame. It is especially used when a protocol gateway/converter is connected. E.g. a ModbusTCP / ModbusRTU converter has got one IP address and several serial slaves. These serial slaves are addressed with MB_Unit_ID.

You must use 3 in MB_Unit_ID.

Error 8383 means that the server answers with exception code 2:

The data address received in the query is not an allowable address for the server.

Both errors 8383 and 8384 indicate that the server can't process the request.

This FAQ may be of interest for you.
The documentation of the 3rd party device looks like they use the addressing of the application layer. If not, you won't be able to read the battery status with S7-1200/1500. It would only be possible with the Modbus blocks for S7-300/400.

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10/20/2014 11:59 AM	Rate (1)
GLouw Posts: 5 Rating: (1)	Hi Kualpuappe, After 2 weeks I finally got it working. I connect with the Sunny Island Webbox to the Sunny Island 6.0H. With the webbox being the Modbus gateway and the inverter being the slave with init ID 3. In the Sunny Island document it states the address I am looking for is 30845. For the S7-1200 to work I used address at MB_DATA_ADDR = 430845. (Read a post a while ago about adding the 4) Why is this? Thanks for all the help. Regards Gerhard
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10/20/2014 1:35 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (323)	Hello Gerhard, there are two ways of addressing: data link layer and application layer. Most of the vendors don't define which way they are using and you can only guess.... Regards, Kaulquappe
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Modbus TCP Client

Created by: GLouw at: 10/7/2014 3:39 PM (12 Replies)

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