Communication protocol CR/LF

Hi
Can some one help me to understand CR/LF protocol. Is there any converter to convert modbus to CR/LF ?
Please help.

"CR/LF" stands for "Carriage Return / Line Feed".

These are functions from old-fashioned typewriters that were carried over into computers as part of the American Standard Code for Information Interchange (ASCII).

A "carriage return" means the return of the character position cursor to the left margin.

A "line feed" means the moving of the cursor one line down.

Both are typically used as the final characters in a single line of ASCII text.


There are two common variants of Modbus that can run on a serial communication link.

The most common one is called "Modbus RTU", and encodes its data in unprintable characters.

The less common one is called "Modbus ASCII", which encodes its data in printable characters. Modbus ASCII frames typically do end with a Carriage Return and a Line Feed.

So if your question is really "is there a device that can convert Modbus ASCII to Modbus RTU", the answer is "yes, many of them."

Ken Roach said:

The less common one is called "Modbus ASCII", which encodes its data in printable characters.

Click to expand...

Although the register values in a Modbus ASCII message are ASCII characters, each 16 bit register consists of four ASCII characters: 2 hexadecimal characters for each 8 bit byte. So a data value is 4 hex characters. A Modbus ASCII message might well be printable but it is not really readable.

L

At one time, printers used a form of a CR/LF protocol.

A printer protocol is data dump on a periodic basis, every time interval or on host demand/command .

The periodic basis time interval is not consistent with Modbus because Modbus is a master/slave protocol where the master requests data and the slave replies with the data. A device that spits out data on a periodic basis pays no attention to a Modbus master request.

Modbus was designed for dealing with quasi-realtime data, the most recent data value. Although there are a couple Modbus Function Codes that deal with transferring blocks of data, like a set of historical values, there are very few, if any, Modbus devices (Masters or slaves) that implement those Function Codes.

So the prospect of a Master requesting data from the past 5 minutes or past hour does not have a high probability of success.

I suspect that you need a custom algorithm to capture periodic bursts of data from whatever it is that is generating the data using a CR/LF protocol.