may be off-topic: CAN-bus, Modbus, RS485, TCP-IP

IP Address Questions and AnswersCategory: Windows Networkingmay be off-topic: CAN-bus, Modbus, RS485, TCP-IP
Storm08 asked 3 years ago

Hello all. I work on industrial Generators. These systems make use of many different communication methods. CAN-bus/Modbus between the Engine Control Module, the Generator controller, an Internet Bridge, which takes data transmitted by the above systems and converts it to Ethernet so that a Remote user with a computer can monitor the operation of the generator systems & also change settings in the different components.
I am a very curious person. I want to write my own programs for these systems.
However, I'm a little unclear about what these protocols are exactly & how they work.
If anyone can help me by explaining any (or all) of these protocols, I would be most appreciative.
CAN-bus; Modbus, RS232 (serial); RS485; and how they all relate to each other & to TCP-IP. Also, what can be done with them.

1 Answers
Rob Vargas Staff answered 3 years ago

Hi, storm08, and welcome to our little forum. I hope you enjoy it here.

Now, about your question... That does not have a small answer. From what I can tell, there are whole books covering that. So I'm just going to toss a HUGE blanket over the issue, rather than going into detail.

First of all, they are different methods of communication. TCP/IP, however, operates on a different level. Other communications protocols like RS-232/485 create some kind of communication, and TCP/IP (basically) breaks the communication into chunks called packets that get individually routed and put back together on the other end. It is basically a "pure" software standard, which is part of why most people call it a "stack."

RS232 and RS485 are serial communications standards based both on hardware and on software. There are multiple wires designed into the standards that play different roles in monitoring and controlling the flow of data, but the data itself (again, basically) is sent over a particular pair of wires (one goes one direction, the other goes back). There's flow control, parity control, speed control, and so on, but that's the gist of it.

At the most basic, easily understood level, CAN-Bus and Modbus are serial communications hardware standards as well. They are just specially designed for industrial communications and environments, like PLC controllers. You're probably best off looking through the Modbus Group's Web site for further information on that. Most of it is industry news and stuff like that, but they seem to have decent information on their FAQ page. Wikipedia seems to have good information to help you get started, but I don't trust Wikipedia as a tech source. Instead, seek out and follow links they provide to better sources that aren't so vulnerable to possibly malicious change.

CAN-Bus seems to be more network oriented than Modbus, but seems to be essentially the same otherwise. Here's a USA-centric site that seems to have good information. Wikipedia, again, can be a good source of more links to check out for more detailed information.

WHEW! Look at how long this got, and I didn't even go into details! By the way, Wikipedia has info on the RS standards also. I've just used those tutorial pages linked above for so long that I usually refer right to them.

Hope that helps. If you want to program for these, you have a lot of reading ahead of you. Good luck.

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