Modbus serial connection error

Hello Mango Team,

this is a follow up of my previous post (http://mango.serotoninsoftware.com/forum/posts/list/1062.page).

Under Windows 7, I run the following software versions:

I want to add a Modbus serial data source which is an uDAM ND-6530 USB/serial converter. I installed the driver software for that one from the manufacturer. Now I want to add a data point to this data source, namely an IME Nemo D4-Dc. I configured the device, the os-driver and mango to the same baud, parity, stop bit, timeout etc.

When I try a `Modbus node scan', I get this error in the tomcat console:

com.serotonin.modbus4j.exception.IllegalFunctionException: Function code: 0x7d
at com.serotonin.modbus4j.msg.ModbusResponse.createModbusResponse(ModbusResponse.java:6
at com.serotonin.modbus4j.serial.rtu.RtuMessageResponse.createRtuMessageResponse(RtuMessageResponse.java:37)
at com.serotonin.modbus4j.serial.rtu.RtuMessageParser.parseMessageImpl(RtuMessageParser.java:41)
at com.serotonin.modbus4j.base.BaseMessageParser.parseMessage(BaseMessageParser.java:37)
at com.serotonin.messaging.MessageControl.data(MessageControl.java:181)
at com.serotonin.messaging.InputStreamListener.run(InputStreamListener.java:76)
at java.lang.Thread.run(Unknown Source)

When I try `Modbus read data' I get a red error "No response from slave 209". Slave ID is correct and all. The tomcat log shows the line

tried to access field gnu.io.RXTXPort.IOLocked from class gnu.io.RXTXHack

I found this error posted here
http://mango.serotoninsoftware.com/forum/posts/list/874.page

and here
http://mango.serotoninsoftware.com/forum/posts/list/297.page#1392

but I could not find a connection to my problem. As far as I can see, IO locks up and there is no return. I am no expert in serial bus communication, only getting my feet wet. Can anyone point me in the right direction?

Thanks for reading and Best Regards,
Michael Bach

Hi Michael,

Have you tried reading the slave with another modbus software like modbus poll? This would help you verify if it's a problem with your adapter or a problem in Mango.

Thanks,
Joel.

This message was edited 3 times. Last update was at 27/02/2012 10:53:45

Hi and thanks for the hint Joel,

I am trying right now with the modpoll tool from here.

My first call was

which returned an illegal data address error (I do not remember exact wording). When I tried to modify the data type on subsequent calls to modpoll.exe, I get the error

Serial port already open!

I also tried with the -1 option to just poll once - same result. Do I have to close the port manually? I could not find any documentation on this and as far as I can see there is no other application using that port. As I said, I read up about modbus but do not have prior experience with it.

Thanks for your help,
Michael

Edit #1: I figured out which application occupied the port. Now I am experimenting with the data types and will report when I run into further issues.

Edit #2: I figured out the correct data type and for the call

I get the error

Illegal Function exception response!

I do not see how I can change the function in modpoll. The device expects a function code 0x03 to read one or more consecutive words (1 word = Bytes).

Edit 3: Since the call

works (reads out the device identifier in this case), I assume now that there is nothing inside the 0x1000 register, since a poll to that reference fails. So now I need to check whether my device is storing the values correctly, right?

My previous post became too bloated to quickly make sense of it. I leave it here so that it can serve others with similar hardware to approach this issue.

After several hundred command line tries, I ended up with the correct one. For reference:

As a side note, reading the manual DOES help (for the IME NEMO D4-Dc slave in this case).

Also, using these settings I can successfully read that value in the Mango `Point locator test'. However, the Tomcat log still shows the line

tried to access field gnu.io.RXTXPort.IOLocked from class gnu.io.RXTXHack

Now I wonder whether this "error" gets significant in terms of preformance or stability once there are more slaves and data points (each polled every second or so)?

Thanks,
Michael