Formatting command/response to Serial Port using RS-232

[LeroiVinncent]

I am trying to write commands to change the settings on a device using RS-232.  I am unsure how to best format the string command.  Attached is my VI and some images from the user manual of the device on how the messages should be formatted. 

[RavensFan · Accepted solution]

It seems like what you are doing is okay.  It is a combination of control codes (hex 02 and hex 03) and visible ASCII characters.  Make sure control codes are in hex codes display like you have, but make the display style visible so it is obvious.

Since your response end with a carriage return, you should make your termination character "D" in the constant wired to the VISA Configure.  And set the radix to be visible on that constant so it is obvious it is hex.

[LeroiVinncent]

So just some clarifying questions:
1. The termination character should be "D", and with the radix on it says "xD" and this should be in hex format, correct?

2. Do I have it correct that the checksum includes the values between STX and ETX? (not including the STX or ETX)

3. When I concatenate the string constants, should STX and ETX appear as hexadecimal [x02] and [x03] ,respectively? and the other commands such as *CALHH200000, are those to be in "normal display" in the program? How does the * character work?

Thank you,

[LeroiVinncent]

Also for the checksum I enter *CALHH200000 but I don't get a hex value of "B1" like it says in the example.

[RavensFan]

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@LeroiVinncent wrote:

So just some clarifying questions:
1. The termination character should be "D", and with the radix on it says "xD" and this should be in hex format, correct?

2. Do I have it correct that the checksum includes the values between STX and ETX? (not including the STX or ETX)

3. When I concatenate the string constants, should STX and ETX appear as hexadecimal [x02] and [x03] ,respectively? and the other commands such as *CALHH200000, are those to be in "normal display" in the program? How does the * character work?

Thank you,

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1.  Yes.

2.  I interpret it as including the STX and ETX

3.  Yes, STX and ETX should appear as 02 and 03 in the string constants, with an x in the border when you turn on Display Style Hex.  The rest should appear that way in normal display.

[jamiva · Accepted solution]

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@LeroiVinncent wrote:

Also for the checksum I enter *CALHH200000 but I don't get a hex value of "B1" like it says in the example.

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I was able to calculate the Checksum "B1" for the command using this algorithm

However it doesn't work with the "Response". I get "CB" vice "CA". Could it be a typo in the users manual?

If you look at syntax for the response data, it specifies a "*D..." but the example uses a "#D..." No matter which symbol I use, it still doesn't result in the example's checksum.

[crossrulz]

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@jamiva wrote:

However it doesn't work with the "Response". I get "CB" vice "CA". Could it be a typo in the users manual?

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Looks like you are off by exactly 1 bit.  So 1 character is off.

Not likely the problem, but I am noticing a space in the response that is not in the command.  How sure are you that the space is supposed to be in there?