VISA read buffer acting differently

[50616d656c61]

Hello,

I have a force gauge (MARK-10) which I want to read the force and display it in LabVIEW.

I found a code which I added some extra code in it, and it works perfectly. But when I wanted write my own code, because I wanted to include motion control as well then it didn't work. So I tried to read only from the force gauge once again but I wrote another code from scratch exactly the same as the first one, but it still doesn't work. And I really can't see what the difference is, do you know what the problem could be?

file, forceGauge (the one that is working): reads very smoothly. the indicator shows the value all the time.

file, test stepper and force gauge (not working): displays *51 in the read buffer, and it flashes in the indicator.

Grateful if you could help me.

[DailyDose]

I cannot download and view VIs.  Any chance you could also take screenshots and post those?

[RavensFan · Accepted solution]

In your force\stepper VI, you are sending ?\r,  as in a literal question, backslash, r because your constant is in normal display mode.  In your force gauge VI, your control is in \code mode so you are sending ?  carriage return.  I'm sure that is error #1 in the force/stepper VI.

In both VI's, I see a problem,  You are writing a command, then immediately doing a "bytes at port".  Since you haven't given any time for the device to respond, you probably have 0 bytes at port and read nothing that iteration.  Bytes at port is the wrong thing to use about 95% of the time.  If the response has a termination character (you set up the serial port with a line feed as the termination character), then use it.  Read a large number of bytes and the response will come back and terminate with the linefeed character.  You won't need the bytes at port and you'll have a complete response.

[50616d656c61]

Here are some screenshots.

[GerdW]

Hi pamy,

when you use string constants with \-codes you should ALWAYS make the display style item visible!

Set your string constant to \-code displaymode, then correct your string content…

[50616d656c61]

Of course, I totally missed that. Thank you so much.

And thank you for the feedback, I'll try it out.

[billko]

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@GerdW wrote:

Hi pamy,

when you use string constants with \-codes you should ALWAYS make the display style item visible!

Set your string constant to \-code displaymode, then correct your string content…

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This practice should be a subset of "if you are displaying any control, indicator or constant in a non-default fashion, always indicate it in the appropriate manner".  e.g., display style for a string, radix for a number, etc... imagine mistaking 100 decimal for 100 hex.

[crossrulz]

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billko wrote:  imagine mistaking 100 decimal for 100 hex.

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I inherited a project where that happened at least 10 times a day (hardware guy was in hex while the test guy was in decimal).  No wonder the project took WAAAAAAAAAAAAY longer to do than it should have...