End of data in serial Communication

[velkumar10]

Hi,

  Am using Pic controller and labview for visual inspection of my sytem. Am controlling 4 Motors using my PIC controller.I have interfaced my pic controller with labview through NI_VISA. Snippet represent the manual serial data communication.When I connect my PIC controller with Labview data follows continously. Now i want to differentiate 1st set of data from 2nd set. Plz help me guys.. Thanks in advance

[crossrulz]

Need to hit some issues with the serial port communications first.  Is the message length always 8 bytes? If so, you do not need the delay nor the Bytes At Port.  Just tell the VISA Read to read 8 bytes and it will wait for them to come in.

You really should give us more information on the communications protocol you have set up.

So you want to keep a history of the data?  How far back do you want to view the history?  How long will this run for?

[GerdW]

Hi velkumar,

another reason to get rid of BytesAtPort: you have explicitely enabled the TermChar!

So you just need to wire a sufficient high number at "Bytes to read" at VISARead…

[crossrulz]

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@GerdW wrote:

another reason to get rid of BytesAtPort: you have explicitely enabled the TermChar!

So you just need to wire a sufficient high number at "Bytes to read" at VISARead…

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I almost wrote that myself.  Then I looked at the data being read.  There were 8 bytes read, all of which were data.  Therefore there was no termination character.  This is one of the reasons I asked for more clarification on the protocol being used.

[RavensFan]

Except the scan from string shows a format string of /%d/%d/%d/%d.   Is the forward slash some sort of delimiter between data items?  (Kind of an odd choice.)

The OP must have put in in there for a reason.  A reply back that clarifies what the data looks like certainly would help.

[velkumar10]

hi ,

   Byte at the port is variable. No I dont want to save my history. when I connect PIC controller with labview, the data will be sent continously from PIC controller. I just want to process the data. For eg: If the data from the PIC controller is 1111 0010 , 1st I want to process HSB ie. 0010 and later that opertion I want to process LSB ie. 1111. For each loop i wil get data from PIC controller, so i want to process the HSB 1st and then LSB.

[GerdW]

Hi velkumar,

If the data from the PIC controller is 1111 0010 , 1st I want to process HSB ie. 0010 and later that opertion I want to process LSB ie. 1111.

You can try this:

I prefer "HSB" (H = high) for th eupper bits in a byte and "LSB" for the Lower bits…

[RavensFan]

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@GerdW wrote:

Hi velkumar,

I prefer "HSB" (H = high) for the upper bits in a byte and "LSB" for the Lower bits…

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Never heard of HSB before.  I think saying LSB for the lower bits is too confusing when everyone knows of it has Least Significant Byte.

Just using the word byte is inaccurate because each 4 bits in a byte are known as nibbles.

[crossrulz]

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@RavensFan wrote:

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@GerdW wrote:

Hi velkumar,

I prefer "HSB" (H = high) for the upper bits in a byte and "LSB" for the Lower bits…

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Never heard of HSB before.  I think saying LSB for the lower bits is too confusing when everyone knows of it has Least Significant Byte.

Just using the word byte is inaccurate because each 4 bits in a byte are known as nibbles.

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So the accurate sayaing here is MSN and LSN (Most Significant Nibble and Least Significant Nibble).  Yes, I have used these acronyms before.