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Modbus RTU (RS485) configuration

Created by: colomer94 at: 4/6/2021 12:42 PM (4 Replies)

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4/6/2021 12:42 PM	Rate (0)
colomer94 Member Joined: 2/14/2020 Last visit: 10/1/2024 Posts: 2 Rating: (0)	Hi everybody, I am having some issues when setting up the advanced IOT2050 with RS-485 serial communication. With IOT2040 I used the iot2000setup command and configured the port, apart from using the "switchserialmode" on the command line to make sure everything was working properly. With the new IoT's I can't establish communication and I think the problem is in the / dev / ttyUSB0 port configuration. Could someone tell me how to fix this problem ?? Thank you so much! Roger Colomer

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4/7/2021 4:38 PM	Rate (0)
Fe_lipe Silver Member Joined: 12/12/2016 Last visit: 4/8/2024 Posts: 640 Rating: (60)	Hello, If you are using the Advanced IOT2050 /dev/ttyUSB0 is indeed the correct interface. A config in iot2050setup should be enough, with no need of using switchserialmode actually, but both should work likewise: (ignore sudo if you are root) Did you leave setup and hold times to their default value? Are you using the Modbus Nodes in node-red as a Client? Maybe you could provide us your Node-Red Flow. And what device are you using as Modbus-RTU server? Please also verify the type of serial cable used e.g null-modem cable (pin 2 and 3 swapped) vs straight serial (the one you need). Best Regards!

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4/21/2021 10:51 AM	Rate (0)
colomer94 Member Joined: 2/14/2020 Last visit: 10/1/2024 Posts: 2 Rating: (0)	I'm trying to connect a Schneider M421, to do this I use the python code that worked perfectly with the IOT2040 (changing the communication port to / dev / ttyUSB0) I used the same cable connection I still think it is an IoT port configuration issue. The comunication paramaters are: Baudrate: 38400 Lenght: 8 bits Stop bit :1 Rs 485

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4/21/2021 6:21 PM	Rate (0)
Fe_lipe Silver Member Joined: 12/12/2016 Last visit: 4/8/2024 Posts: 640 Rating: (60)	Hello, What is the MLFB of the IOT2050? (just to be sure you have indeed the advanced version and not the basic). In the configuration of iot2050setup you should also be able to setup the setup and hold times if you indeed have the Advanced board. I can recommend the following procedure: Set both timings to 0x0005, select terminate resistor on. A message that a power-cycle is required for these changes to take effect should appear: Pull off the power cable of the IOT after selecting OK. The changes should now have taken effect. I was able to read, using pyModSlave on my PC as a Mobus-RTU slave (check screenshot in attachment) On my Iot I have actually only conneted Pin 1 and 2 of the X30 Com interface. Let me know if you are able to solve your issue! BR PS: are you doing everything as a root user or did you add a new user to the IOT? If you have created a new user, please make sure this user is also in the linux "dialout" group or else you wont be able to access serial devices Attachment modbus-rtu.png (1287 Downloads)
	Last edited by: Fe_lipe at: 04/21/2021 18:25:48
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6/19/2023 8:27 AM	Rate (0)
Jen_Moderator Diamond Member Joined: 6/19/2017 Last visit: 9/6/2024 Posts: 8175 Rating: (172)	New question published by U_2f1b6ae2-97ff-4a26-b160-e82ec2fb5081 is split to a separate thread with the subject Is there a command to use to find out if the machine is basic or advanced?. Best regards Jen_Moderator

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