Bytes to Port property node. When to use and when not?

Hi all

Ive frequently used bytes to port property node performing bed series and have not experienced any problems.  I've heard mixed on this subject reviews and I would like to know when to use and when not to use it.

Thanks for any input.

I will start by when it should not be used.

When there are (as readable) ASCII data to come through and it is separated by a termination character.  Select the stop character and read more bytes than you ever expect a given message.

When there are binary data, but a protocol where you know clearly how the message package is put in place.  In this case, you want to disable the stop character because any octet can be given legitimate and be interpreted as the stop character.  With these protocols, if you know the message is always X bytes, read X bytes.  If the message is of variable length, but the Protocol is set to tell you low for a long time the message is, and then make partial readings.  So if each message starts with 2 bytes that says follow X bytes.  Then read 2 bytes, which converted to a number, then read this number of bytes.

When to use:

The only time will really use bytes to the port is if you use a terminal of the installation type.  Just enter and display on-screen what never happens happened at the port since the last time it was read.  When you don't care where are message breaks.

If you use bytes to the port and care message breaks, then you're obligated to all your new message concatenated to a string, you store in a shift register and each reading analysis through data to determine if you have a complete message and valid.  If you do not, do nothing and go back and read more.  In fact, you will need to run through the chain of data several times in a row before coming back to reread in the case where the message ever resulted in a single reading packets.

The vast majority of applications falls into one of the above situations.  The last situation is not as common, and if you use bytes to the port with a system of e-mail that has defined a defined protocol or packages, you do a job more in programming to maintain a software buffer of data as well as the hardware buffer to the serial port.

Tags: NI Software

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