Modbus Ethernet

[JCNT]

I used Modbus Serial of IAS to communicate with a device which measures voltajes and currents, and the communication between them was successfully. Now, I want to communicate with this device using Modbus Ethernet, so I connected it to Serial to Ethernet convert (it is not a N.I. converter). I have not been able to establish any communication so far and I have got an error message which is “NO RESPONSE FROM THE SOCKET”. I know that Modus Ethernet uses to communicate with an Ethernet device the 502 remote port, but I do not know which remote port the Ethernet device has to use to communicate with the Modbus Ethernet driver. Has it to be the 502 or up to 1024 port? I will appreciate so much any help that you can give me because I have spend a lot of time with it.

My regards,

Juan Carlos Nieto
Quito-Ecuador

[DimensionFinder]

Hello Juan Carlos:

Are you using the Modbus object in Serial mode or ethernet mode? You should be using the object in Ethernet mode and set your communications settings (IP address of the device and the Identifier, if any) accordingly.

Let me know if this helps......

[JCNT]

Hi,

I am using the Modbus object in Ethernet mode. I set the IP address of the Serial to Ethernet converter (UDS100B Lantronix), but the identifier is the electric meter address which is connected to the UDS100B Lantronix serial port.

My system is:

• A computer which has the IAS and an IP address.
• A Serial to Ethernet converter which has an IP address, a local port (502), a remote IP address (IP address of the computer which has the IAS), and a remote port (6342).
• An electric meter which is connected to the Serial to Ethernet serial port, has an address (1), and uses Modbus Serial.

I also configured both the electric meter and the Serial to Ethernet converter to 9600 bps, RS-485 two wires, 8 bit, no parity, and 1 stop bit.

I already established communication between the IAS and the electric meter using Modbus Serial, but now I want to communicate them using Modbus Ethernet. What about the message “NO RESPONSE FROM SOCKET.”

Thank you very much for all your help and I will be hoping for your answer.

My regards,

Juan Carlos

[AllanS]

Hello Juan Carlos!

I want to make sure I am understanding your question. You have a Modbus serial device that is connected to a serial to ethernet converter. In lookout the Modbus Serial object works correctly but the Modbus ethernet object does not work correctly. If your modbus device is a serial device you will not be able to use the modbus ethernet object. Lookout is unaware of the conversion so all it sees is a Modbus serial device.

Please let me know if I am misunderstanding the question. Have a great day!

Allan S.

[JCNT]

Hello Allan,

I am using Modbus Ethernet because the device which receives the message from the IAS is the serial to Ethernet converter.Then, it converts the message to serial and sends it to the serial Modbus device which is connected to the serial converter port. Now, I know that this serial to Ethernet converter does not support Modbus, for that reason the data which arrive to the Modbus device were wrong. If I use a Serial to Ethernet converter which supports Modbus, Will I able to establish communication between my serial Modbus device and Modbus Ethernet? Thanks so much and I will be hoping for your answer.

My regards,

Juan Carlos Nieto

[mrak1]

Hi,

I don't mean to jump into your discussion but I have come across this scenario before. Modbus Ethernet uses a different protocol than Modbus Serial ( added extra bytes for the communication in the header and other things). The easiest solution for me was to use a pair of VLinx ESP902 from B&B Electronics. Doing this allows you to configure the Modbus Object in Lookout as Serial and not have to worry about the actual communication. It may be cheaper to purchase a Modbus Enet to Modbus Serial converter ( one that can translate the protocols) BUT you will have to modify your application every time you change between communication options..

I hope that this helps!

Mike

[JCNT]

Hi Mike,

Does your VLInx ESP902 support Modbus? because if it doesn’t, you mean that I can use 2 Serial to Ethernet converters which don't support Modbus and I don't have to buy the ones which support Modbus and are more expensive.

If I use 2 serial to Ethernet converters, I must have a free serial port in my computer. However, if I use Modbus Ethernet with a Serial to Ethernet converter which supports Modbus, I just use the network. Would it be an advantage?

I am not sure if a Serial to Ethernet Converter which supports Modbus will translate the Modbus Ethernet protocol of the IAS, because it is not a N.I. device. Is Modbus Ethernet a standard protocol and any Serial to Ethernet converter which support Modbus will be able to translate it?

Thank you very much for your help, and I hope you can help me.

My regards,

Juan Carlos