Ccommunicating with Serial Instruments Using GPIB-RS232 converter

[Dennis_Knutson]

The MAX has idn default but that only applies to standard GPIB. Most serial devices will not support that.

You should be using VISA for all communication. Never use the low level GPIB functions.

I think I used D mode the last time I had to use one of those. I did not enjoy the experience

[RavensFan]

Serial is the generic term for a type of communication.  RS-232 is the physical definition of how the wires send the signals.  RS-232 and "serial" are often used interchangeable.  RS-485 is another definition of how the wires send signals.  Google those terms to learn more.

GPIB is another physical connection method.  I don't know whether it is serial or not, but it is dramatically different from RS-232 and RS-485,

To be able to communicate with the Omega device, it must have the RS-232/485 board in it.  And if it does, you can communicate with it.  You need to find the manual that tells the commands and responses that it recognizes.

Messing with the GPIB converter is a waste of time.  You have least doubled the complications if not tripled.  I highly recommend leaving that out and getting the communicaiton working with a regular USB-RS-232 converter.  Then you know that works and can demonstrate it to the professor.  If he still insists on throwing in GPIB (and as I said, he is clueless if he is), at least you have part of the problem solved before you throw in the complicaitons of GPIB.

[johnsold]

I can see some value in converting RS-232 to GPIB -- IF there are other GPIB instruments in the system and the controller and software are already set up to use that.

It appears that Omega has a separate manual for the communications to the DP-41. From a quick glance at that manual it may not be a straightforward task to get communications running. There are many options for setting it up and the defaults are not immediately clear. For someone not at all familiar with serial communications if could be a nightmare.  Try to find someone on campus who knows serial communications who can help you.  Often an experienced person can work out what needs to be done in an hour, while you might spend a week studying the manual and still be confused.

GPIB is bit parallel and byte serial. The data bits and several control/handshaking bits are transmitted in parallel for each byte.

Lynn

[cnoyes23]

Thanks for your help and patience. 

johnsold: That seems to be the idea. There will be other GPIB instruments in the system (an Agilent 34410 multimeter and maybe one more device). 

RavensFan: There is another manual in the lab that has communications instructions. It gives instructions in ASCII. Is that the language used in serial communications?

Dennis: Are there generic VISA functions to communicate with any serial device or will there be specific codes in the Omega manual?

[Dennis_Knutson]

There is no such thing as generic serial commands. Sometimes they are ASCII bit often they are not. RTFM.

I don't think the fact that you have other GPIB instruments is st all relevant. The converter is expensive and just complicates your network.

[cnoyes23]

I found a guy on campus who knows serial communications and will be around next week. 

In the meantime, I'm trying to understand some of this myself. I read the manual (and attached it) but the formatting is still pretty confusing to me. Does anyone have any hints on using the commands in there? (Apologies if these questions are overly simplistic to experienced people)

[Dennis_Knutson]

The manual send remarkably complete and thorough. You need to prepend the recognition character to all commands and terminate each command with a carriage return. Just a bit more complicated than the GPIB commands you would be using for the other instruments. There are many ways to correctly format the commands in LabVIEW but I would suggest you first do your debug in MAX. The only thing you need to understand is that a carriage return in MAX is entered by typing \r. Be thankful that you don't need to calculate a checksum and send that as well. It could be so much worse.

[cnoyes23]

So using the recognition character * and the carriage return \r, I should write commands in the viWrite section of the VISA panel in MAX?

Also, you said it's not that different from communicating with GPIB in MAX. I haven't really done much of that, but would the commands just be the various structures in the communications manual or is there somewhere else I can look for them? 

[Dennis_Knutson]

The only place that would have the commands is the manual for your instrument.