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Re: No such file or directory: '/dev/ttyRS485'

19 Dec 2022, 23:38

I bought another RevPi Connect+ device but I have again the same modbus communication problem with Modbus RS485 on /dev/ttyRS485

- if i use '/dev/ttyUSB0' (with usb/rs485 adapter) all work correctly !!!
- if i use '/dev/ttyRS485' (with two wire +- connected to modbus rs485 pinout) doesn't work !!!

Why the /dev/ttyRS485 is very problematic? How can you check surely the problem and how to solve it?

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Re: No such file or directory: '/dev/ttyRS485'

20 Dec 2022, 07:21

Please provide logout put from dmesg and error messages if applies.

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Joined: 12 May 2019, 16:15
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Re: No such file or directory: '/dev/ttyRS485'

16 Jan 2023, 11:44


I'm having the same problem with a Connect. I cannot get modbus to work in Codesys with RS485 connector on the front. (see image in this post: ... sys#p13118)

I followed the comments from Nicolai and turned off PiModbus Master and Slave in Pictory.

I also followed the Codesys steps here: ... u-slave-2/ - This suggests to use tty/USB in the CODESYSControl.cfg settings.

I checked these steps per an old post from Amar: ... ys-control

Somebody is suggesting to use /ttyRS48 (no '5') and set to port 6: ... 2239cdd18/ - but that's not working either.

I'm a bit lost with all these different options? What is the official suggestion from Kunbus? And how should i troubleshoot this: do i check dmsg first? Can I check any log in Codesys that may be helpful?


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