Can non-data lines in Parallel Port be accessed with VISA?

[rocket_author]

Hello all,

Wondering if anyone can confirm or dis-confirm if VISA can access the lines of a parallel port besides D0-D7; if so, how would one go about this?

[SerJames]

Hi rocket_author,

Out of curiosity what is it you are trying to achieve? A little more context would likely be useful to formulate a better answer. Looking at the pinouts available for a parallel ports

http://en.wikipedia.org/wiki/Parallel_port

there appears to be a limitation to the available ports that you can access. It appears D0-D7 are the designed data ports and I am not aware of any other parallel port hookups.

Regards,

[rocket_author]

Hi James,

What I have is a legacy system that uses the parallel port to send discrete signals from one computer to another; being that our new system is Windows 7, we can no longer use the In Port.vi and Out Port.vi, which allowed access to the Data, Control, and Status ports.  I know that the "easy" solution would be to simply get an inexpensive D I/O card and use that instead, but I have significant push-back from management stating that the time it would take to update drawings, go through change review boards and get approval from our customer would be prohibitive, if not nearly impossible.  Thus, I'm trying to make this parallel port work with Windows 7.

It's easy enough to get to the Data port, you simply send the string to the Write command in the VISA menu and then select which port to use; but, it seems that only allows access to D0-D7.  What I need access to is D0-D7, S3-S6, and C0-C3.  With In Port.vi, you'd simply bump the parallel port address up one or two in hex (if 0x378 was Data, then 0x379 was Status and 0x37A was Congtrol).  With the VISA option, I don't see the ability to do this.

[rocket_author]

I was poking around the Instrument I/O area and found some interesting VISA options under Advanced, it seems there are several options under Register Access; perhaps these are what I need to get to the Status and Control registers?

[SerJames]

Have you had opportunity to look through our knowledgebase on the topic?

http://digital.ni.com/public.nsf/allkb/B937AC4D8664E37886257206000551CB?OpenDocument

It has an indepth guide to communicating with a parallel port in LabVIEW and should help give you the tools to use NI-VISA to get this done. It is possible that there could be some limitations and a cheap D I/O card may be necessary but I think that KB should get you well on your way.

Regards,

[rocket_author]

James,

I have gone through that document several times, but the main problem is that I'm using WIndows 7, x64 so that document is largely obsolete; with 64 bit systems, In Port.vi and Out Port.vi no longer work because the I/O ports have been locked down by Microsoft because of "security concerns".  

Also, the document you mentioned shows how to write to the data lines (which is great), but makes no mention of if reading the Status register or writing to the Control register with VISA, only via the obsolete software that no longer works (In Port and Out Port).

To boil my question down, I'm basically asking if the VISA functions will allow control and status register access of a parallel port in Win7 x64.

[SerJames]

It appears the VISA In and Out vi's within the Advanced -> Register Access would be your closest bet as it will write/read from the specificed address space + offset. 

Let me know if those don't provide the functionality you need for your particular application.

Regards,

[rocket_author]

I was thinking the same thing about those register access functions...is there any literature that NI provides that describes those functions, beyond the contexual and in depth help?  I feel like I'm just randomly connecting things together instead of really understanding what the code is doing, especially because I'm not doing work in GPIB or VXI buses.

[SerJames]

Hi rocket_author,

Sorry for the delay in response, somehow notification of your reply got lost in the internet void somewhere. To answer your question, there does not appear to be much in teh way of documentation beyond the help. It appears that these functions are specific to PXI/VXI and may not be an option for general VISA. DIO cards appear to be the only option you have that I can find reliable information on.

Regards,