Serial Com - Sending commands via port RS232 etc

[dshif]

Hi,

I am looking to create a vi that is able to read ASCII commands from the instrument and write commands. I have looked at different examples and i think i have an idea on how to go about creating the communication. But i am trying to create sequence structure because there will be different commands the operator will be inputting. The problem is some of the commands that are being put in are a little long, there is a checksum included but i believe that the checksum is actually being done, by the module so i don't think ill need to create a checksum vi. ill have  a snippet of some of the commands, hopefully that'll give you some idea of what I am looking at. i just want to bounce ideas off and maybe get some idea of the best way to go about creating different commands that work in the same vi.

[crossrulz]

1. I like to make libraries and/or classes for my instruments.  In these, you can have a different VI for each command/query.

2. You will probably need to make a checksum VI.  You did not include any information on the messages you will send, but at the very least you will want it to verify you got a proper message.

3. No need for a Sequence Structure here.  Proper error handling will create the data flow you need to sequence your code.

[dshif]

I believe that is what I will have to do. Sorry i should've attached it, its attached now. can you elaborate on what "proper error handling"  would look like? Regarding the Vi's why do you think ill need a checksum vi? the device that i am sending these commands to already has a checksum calculation in it.

[crossrulz]

You have to calculate the checksum and put it in your message.  That is how the instrument knows it got a valid message.  It is clearly there in the protocol.

[dshif]

So I have the checksum calculation working correctly, but im running into a problem. What i am trying to do is let the user pick between different commands and based on those commands the system is able to adjust to it. For example, i would the user to be able to click on the position control mode, that would then input the % that would allow them to regulate where the position *i have attached the vi* i would like some pointers on how to do that. Also if you have any advice on my current setup i would be more then willing to correct it !

[crossrulz]

1. No need for ANY of those local variables.  Use wires.  This will also remove the need for the sequence structure.

2. Again, make a VI for each command you want to send.

3. Use an Event Structure.  This way you only have to send the commands when something actually changes.