The Industrial Raspberry Pi Forum

Hi,
I am about to get my PLC connected to a number of components next week, and i am just trying to preempt the troubles. I am using node-red for the modbus functionality.
I have a number of Modbus devices connecting to the system. 1 is TCP and 3 are RTU. All the RTU based device will connect to the rs485 connection on the connect+.
From other posts i have seen rtu-buffered helps any problems and making sure each slave has its own id and informtation is correct.

Is there any options in the noder-red-contrib-modbus node that i should avoid?

Which address is used? /dev/tty , /dev/usb0 etc

Any information or problems and work arounds would be greatly appreciated

Mitchell

Hello Mitchell,
It's great that you're proactively looking into potential issues before connecting your PLC to Modbus devices using Node-RED. Here are some considerations and tips:

• Modbus Node Configuration:

Make sure to configure the Modbus nodes correctly for TCP and RTU connections. Set the mode to TCP for the TCP device and RTU for the RTU devices.
For RTU devices, use the "Serial" option in the "Connection" field. Specify the correct serial port, baud rate, and other relevant settings. The address in this case will be the Modbus slave address.
For TCP devices, set the server IP address and port in the node configuration.

• RTU Devices and RS485:

Since you have RTU devices connected to an RS485 network, ensure that each RTU device has a unique Modbus slave ID. This is crucial for proper communication with individual devices on the RS485 network.
Use the rtu-buffered option for RTU devices. This helps in handling timing issues and improves the reliability of communication on RS485 networks.

• Serial Port Configuration:

The address like /dev/tty, /dev/usb0, etc., depends on your system and how the serial ports are identified. Make sure to use the correct address for your RS485 connection. You can usually check this using commands like ls /dev/tty* or ls /dev/usb*.

• Troubleshooting:

Node-RED provides some debugging tools. You can use the debug node to inspect messages at different points in your flow, which can be very helpful for troubleshooting.
Check the Node-RED logs for any error messages related to Modbus communication. This can provide insights into potential issues.

• Timing and Delays:

When working with RS485 networks, consider the timing and potential delays in communication. Modbus RTU over RS485 can be sensitive to timing, so configuring appropriate timeouts and delays can be crucial.

• Node-RED Version:

Ensure that you are using a version of the node-red-contrib-modbus node that is compatible with your Node-RED version. Node-RED and its nodes are regularly updated, and using compatible versions can prevent compatibility issues.

Considering the seamless integration and enhanced flexibility, we recommend utilizing Modbus via Pictory for a more streamlined and efficient communication protocol, offering advanced features tailored to optimize your specific industrial automation needs.
You can find some tutorials on the Links below.
modbus on Revpi connect
Modbus TCP
Modbus RTU
how to connect serial devices

Best Regards,

Ulrich Kouatang Biakoup | Technical Support

Thanks I will keep this handy next week.
If I were going to use the pictory Modbus setup, would the information be available to node-red interface through the revpi-nodes?

mitchellday06 wrote: ↑29 Nov 2023, 06:23 Thanks I will keep this handy next week.
If I were going to use the pictory Modbus setup, would the information be available to node-red interface through the revpi-nodes?

Hello mitchellday06,
of course, the information will be available through the revpi-nodes.

Best Regards,

Ulrich Kouatang Biakoup | Technical Support