11/16/2019 9:54 AM | |
Joined: 7/2/2019 Last visit: 11/17/2023 Posts: 3 Rating: (0) |
Hello! I'm using et200sp with ptp communication module ( 6ES7137-6AA00-0BA0), Modbus_comm_load V3.0, Modbus_Master V2.4. I'm reading multiple slaves without errors, but with this particular slave ( Kamstrup 62 water meter with modbus RTU module 6700-67 ), i'm having trouble, i can read it , but i will occasionally get errors : 81EA, 81E7, 81E9. I set up counter, and got DONE 246 times and ERROR 85 times. I have tried different cable with which i can read all other slaves without errors, except kamstrup 62 (one at a time). I have also tried reading this slave with s7-1200 with communication module cb1241, MB_COMM_LOAD V2.1 and MB_Master V2.2 .And the problem stays the same, i'm able to read the slave, but this time i will occasionally get error 80C8. I also tried to use terminating resistor (120ohm), but in this case, the module stops immediatley and gives error 81E7. But i don't think there is the problem, because other slaves communicate even in very long line(40m), but this particular will give errors with 5m long line. Also this is my first project with plcs. Sorry for my english EDIT1: Maybe someone can post some sources, how to properly read rs485 line with oscilloscope? |
Last edited by: AutoGen_4928795 at: 11/16/2019 09:59:53 |
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11/16/2019 1:00 PM | |
Joined: 9/27/2006 Last visit: 9/22/2024 Posts: 12282 Rating: (2685) |
Hello; You can easily locate documents on oscilloscope debugging for RS-485 networks on the web: https://www.sbc-support.com/en/faq/100297/ Goggle for "RS-485 Oscilloscope" and you will find many more links. Hope this helps, |
11/16/2019 4:12 PM | |
Joined: 3/28/2010 Last visit: 9/21/2024 Posts: 1056 Rating: (213) |
Any of the errors could be due to electrical noise on the lines causing bit corruption. So you can take a look with an an oscilloscope, but it wouldn't surprise me if you do not see anything amiss. That RS-485 port is isolated and those tend to be more noise free than those with a grounded signal reference. Let us know what you find. |
12/4/2019 4:30 PM | |
Joined: 1/17/2007 Last visit: 8/21/2024 Posts: 1545 Rating: (537)
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A telegram trace would be very helpful in determining the cause of your woes. |
Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. |
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