@carzten2000, please find the late official 1.9.0 snapshot version here. I recommend using the above official development version instead of the custom build you are currently using (now that the new functionality is merged). I’m afraid that it’s unlikely that it works even there due to different baud rates.
So it works if you remove the slave having different baud rate, eg em23?
I believe there was discussion in this thread regarding the challenges of having different baud rates in the same line. I’m not sure you can really get that working reliably… But perhaps some one else has more information on this?
Technically speaking the binding currently configures (baud rate, parity etc) the serial port in the very beginning, and does not change it afterwards. That alone now causes issues for you as the baud rate would have to be reconfigured again and again to match the slave device requirements. This detail is easy to change though… We could try it out if you like?
If I remember correctly, the binding prints summary of parsed slaves in the beginning . That should make it clear what baud etc will be used.
Can you repeat the test with debug level logging and paste the relevant log snippet here? you can find instructions to logging configuration from the modbus binding wiki page
The whole idea of mixing speed/parity modes etc. down a single wire seems a bit perilous. In theory, the timing of RTU inter-message gaps and suchlike is set by linespeed. Even if cleverness could be worked into the binding to make safe allowances at the master end, you can’t predict how the slaves are going to cope.
The Modbus RTU specification states
"The transmission mode (and serial port parameters) must be the same for all devices on a MODBUS Serial Line."
which means that slave designers need not handle the case in any sensible way.
Reminder - it is possible the particular problem being attacked here is slave-based i.e. one of the devices is entering error recovery when it sees “gibberish” intended for another slave.
Also think that trying to get the binding to cope with it is essentially wasted effort for non-compliant cases. Personally I wouldn’t like to guess how well different hardware and operating system hosts would handle rapid reconfiguring of serial ports to make it feasible anyway.
The “correct” solution here is to set up two serial buses (would that just be a second USB<>RS485 adaptor in this case?)
After reading the reply from @rossko57 I thing that best solution would be to just ad another usb<>rs485.
I going to test this next week, and I will report back with the result.
I didn’t mean to sound snippy about it, like “you can’t do that” !
I’m sure it would work in many cases. The difficulty is that in cases where it doesn’t work properly, the problem may lie in some ‘Black Box’ (Operating system, serial adaptor, modbus slave) outside of your control. No-one will be interested in fixing those because they won’t be seen as broken - “That is not the way to use them”. Note that fully-featured modbus slaves would be counting up more errors than good transfers.
Worse case, you get it working - but then later some small change in host or slave breaks it. Me, I just wouldn’t risk that.
Please do let us all know if multiple serial buses works for you - that may be an untested case (so far) for the OH binding.
Really good that you brought this up! Indeed from the perspective of the rtu slave it is really bad situation if there are many baud rates on the same line.
Therefore will leave the binding as is and looking forward to hear the feedback from the test.
Is it possible to restric modbus.net.TCPMasterConnection to make only one connection per IP:port
As many slaves addet behind one IP the connections become many. Most of the Gateways support one connection.
No debug information about the address of the failed slave. ( ModbusSlave: Error connecting to master: Connection timed out)
and from linux console I see the folloing connections:
netstat | grep 237
tcp6 0 0 192.168.74.235:49395 192.168.74.237:502 ESTABLISHED
tcp6 0 1 192.168.74.235:49396 192.168.74.237:502 SYN_SENT
All Slaves are on one IP address (…74.237) with different IDs
Unfortunately you cannot use the latest stable version to get the new behavior. You need to download the latest development version from here. Please remove the older version before installing the new one.
Please report how it works with the new version. I would recommend using pastebin.com for the logs, makes the thread more readable.
I have two slaves (tcp) configured. If one of them is off it takes about 20 seconds to poll the one that is working.
Is there anyway to avoid this situation?
I´m running OH 1.8.3 with Modbus binding 1.9.0 on Windows 10.
Hi @Botura, can you please paste your modbus configuration please. Which of the slaves return connection timeout.
It seems that connection timeout is 3 seconds by default. Further wait might be introduced by the connection string parameters (see the wiki for details).
Here is my configuration, the slave that is returning timeout is 192.168.0.12.
The timeout seens to be 21 seconds… I´ve tried with the default parameters, ie, just setting host = “modbus:tcp.IOR12.connection=192.168.0.12” but the behavior was the same, except by the retries times.
As I could understand reading the wiki, there is no timeout parameter for modbus tcp slaves, the timeout is used only with serial slaves.
you are correct that there is no way to modify the timeout – in fact, there never has been Nevertheless, I’m still a bit confused why the default 3s timeout is not respected and you are observing much larger timeout period.
Before jumping to any fixes etc, can you please do these steps
Make sure you are using the modbus binding version linked above (just to be sure)
Use simplified config with one modbus slave only, e.g. IOR11. Use 0 for reconnectAfterMillis, interConnectDelayMillis and 1 for connectMaxTries (this you have already). Keep the poll period of 500 (ms) and interTransactionDelayMillis of 60 (ms).
enable debug logging, instructions are in the wiki
Use pastebin to paste 1) configuration and 2) logs
Nevertheless, I’m still a bit confused why the default 3s timeout is not respected and you are observing much larger timeout period.