GPIB to Serial Converter - problem with receiving RS232 and seeing it on GPIB (Service Request 7198845)

[Eagle Eye]

Situation:

I'm trying to use a GPIB to Serial Converter to control a temperatuer chamber controller.

I'd like to use the interface in D mode, so that it is supposed to be transparent,

just a GPIB to RS232 converter with a fixed setup for baud rate etc.

Why:

The PXI chassis I have is practically full and all my regular COM ports are used.

The chamber controller has only RS232 interface.

Easy way you can reproduce the problem:

In order to illustrate the problem I've used it also in G mode, where the commands to the interface and the data use separate GPIB addresses.

I have placed the device in G mode, with address 16 for the interface and 17 for the data (serial) part.

Address 16 replies to the "id\r" query (from MAX) as expected.

As the knowledge base suggests, I have connected the TXD and RCV pin together for a loopback.

Any read from address 17 (using a query or a Write and then a Read) gets EOAB errors.
I have tried to use the various termination characters (\r, \n or a combination) - no deal.

When I use the interface in D mode and connect to the actual serial device (instead of the loopback),

I can see that my WRITE works (commands are executed) but my READ does not -

even when I see a reply with a scope, the NI Spy does not show any data coming back).

[Simran_K]

Hello,

Thank you for contacting National Instruments. It looks like someone is already working on the phone support issue (7198845) and will get back to you shortly.

Regards,

[Eagle Eye]

Thanks for the answer.

However, so far there is no resolution and I was wondering if anybody else has encountered the problem and maybe even found a solution.

Is it possible that I'm the only one using the product?

Thanks

Message Edited by Eagle Eye on 06-19-2008 06:18 PM

[MXI Master]

The solution to this problem boils down to termination characters. The complicating factor is that we are using both the convert box borrow a few settings from both the GPIB and Serial communications.

Solution for G-mode:

The EOS setting must be set on the gpib-rs232 converter box by sending an  the command "eos [X[B]eoschar]<CR>, where X or B is the termination mode

Description	Letter
XEOS—Set EOI* with EOS when sending data from serial device	X
BIN—compare all 8 bits of EOS byte rather than low 7 bits	B

This can all be programmed using either the GPIB VI or with the VISA VIs in LabVIEW.

Solution for D-Mode:

In MAX:

In the GPIB Interface Properties, Under termination, set the "Terminate Read on EOS"  and then select the proper "EOS Byte"

In LabVIEW:

You will need to use VISA to communicate if you want to programatically change the termination character settings. The settings that need to be modified are,
VI_ATTR_TERMCHAR and VI_ATTR_TERMCHAR_EN setting the termination character and enables status respectively

I am currently placing this process in a Knowledge Base Article, and will post a link with pictures once it is complete.

[Eagle Eye]

Thank you very much for your help - it finally works 🙂

It looks like the main issue was the EOI.

Again - thanks for your effort.

EE