ratsept Posted February 14, 2022 Report Share Posted February 14, 2022 Hi, I'm having a really hard time getting UAC-CX-01RS4 attached to a US5/7-x10-TR22 working. I have followed the manuals as close as I can and the software is not giving any warnings or anything but for some reason there is no activity on the RS485 bus. I have checked the bus with a USB-RS485 cable and the PLC is not causing any traffic on it. I have only 3 devices on the test bus - the PLC, the USB cable and an RS485 IO module from Wellpro. The IO module works fine when I send it requests from the USB cable. And I can see the responses arrive over USB as well. But when I run he PLC nothing happens. What I need the PLC to do is act as modbus master and periodically poll the IO module for data. Can you please share some example code of modbus master on RS485 bus? 1 Quote Link to comment Share on other sites More sharing options...
DanT Posted February 14, 2022 Report Share Posted February 14, 2022 Hi Ratsept; Download the UniStream Examples Zip file from the UniStream Downloads section. There are Modbus examples under Communications. The Modbus is set up under protocols and creates a Struct in Global Variables that has data in there about how the communications are working - Attempts, successes, fails, and status codes, and more. Optional - Post your Code and we can review it. DanT 1 Quote Link to comment Share on other sites More sharing options...
ratsept Posted October 17, 2022 Author Report Share Posted October 17, 2022 Hi DanT, I'm sorry to bring this up again but we are still struggling with this. I now have the code that we used for testing and we fail to get any activity on the RS485 lines (checked with oscilloscope to be sure). Can you please advise how to proceed? Tiit katel PWM.22.ulpr 1 Quote Link to comment Share on other sites More sharing options...
DanT Posted October 17, 2022 Report Share Posted October 17, 2022 Hi Rapsept; What version of UniLogic are you using? DanT Quote Link to comment Share on other sites More sharing options...
DanT Posted October 17, 2022 Report Share Posted October 17, 2022 Hi; I reviewed the program. You are not properly triggering the Modbus Read The Tag TAGASITEMP is set up as both the data Tag and the Trigger -- will not work. Change the trigger name to ( say) TAGASITEMP-TRIGGER in the Active Periodic loaction then in the ladder turn that Bit ON to read the coil data each time you want to read the coil. DanT 1 Quote Link to comment Share on other sites More sharing options...
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