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Hi all,
I am very new to Modbus and any form of industrial control although I have a little experience of radio comms (hence the Zigbee radio units I am trying to work with).
I am trying to connect to an SHJ electronics S6889 protocol converter over my network. I can ping the ethernet card and detect that port 502 is listening, and I believe I am connected to the unit. however when I try to read the modbus registers it all seems to go wrong. I am using a ubuntu Linux laptop connected to the S6889 via ethernet. To try and send and receive Modbus data I am using qmodbus. The communications seem to be working at some level. e.g. sometimes I am getting back responses, BUT it is consistently returning "Slave threw an exception" etc etc. every now and again there are responses but they have inconsistent function codes and slave id's, despite the request being the same.
I have also tried to use Modscan32 running in Wine on Linux, but this also returns errors saying the Modbus is timed out. however many times I let it poll, it returns no valid data or slave response. To try and eliminate the network angle, I have also attempted to connect over serial RTU. I've checked my settings and they are correct however I get the same messages.
I am aware of just how limited I am with Modbus and would appreciate any help I could get on this. I realise this forum is for more skilled professionals than me. but I hope that maybe someone can give me a hand on this, even if it is where to go for some more detailed reading or troubleshooting steps.
I am very new to Modbus and any form of industrial control although I have a little experience of radio comms (hence the Zigbee radio units I am trying to work with).
I am trying to connect to an SHJ electronics S6889 protocol converter over my network. I can ping the ethernet card and detect that port 502 is listening, and I believe I am connected to the unit. however when I try to read the modbus registers it all seems to go wrong. I am using a ubuntu Linux laptop connected to the S6889 via ethernet. To try and send and receive Modbus data I am using qmodbus. The communications seem to be working at some level. e.g. sometimes I am getting back responses, BUT it is consistently returning "Slave threw an exception" etc etc. every now and again there are responses but they have inconsistent function codes and slave id's, despite the request being the same.
I have also tried to use Modscan32 running in Wine on Linux, but this also returns errors saying the Modbus is timed out. however many times I let it poll, it returns no valid data or slave response. To try and eliminate the network angle, I have also attempted to connect over serial RTU. I've checked my settings and they are correct however I get the same messages.
I am aware of just how limited I am with Modbus and would appreciate any help I could get on this. I realise this forum is for more skilled professionals than me. but I hope that maybe someone can give me a hand on this, even if it is where to go for some more detailed reading or troubleshooting steps.