Communication interface and communication protocol you really get it right?

I am engaged in automation, before the concept of interface and protocol is always stupidly unclear, very confused, recently enlightened, the land flat ah, today to share with you, I hope to help you.

Two devices want to communicate, the first to have the same device interface, or can be converted to the same interface.

To make a comparison, sheep have 232 serial ports, cattle have 485 serial ports, then obviously, sheep and cattle can not communicate, here ignore the transfer interface, just express this meaning, do not accept to lift the bar.

So, two devices with the same interface must be able to communicate? The answer is definitely no. Having the same interface is just a prerequisite. Another analogy, an American 232-C serial port, a Kazakhstani aborigine also has a 232-C serial port, but the language is not ah, a speak English, a speak do not know what language, how to communicate it? The language here refers to the communication protocol.

So to summarize, if two devices want to communicate, they must have the following two conditions:

Possibility of physical connection: have the same device interface, or the interface can be converted to the same interface.

Software connection compatibility: the same communication protocols supported by the devices.