Writing and Reading the Control and Status bits of the Parallel Port

[wond3rboy]

Hi, i am communicating with the parallel port using the VISA write and VISA Read functions. I have a few questions:

1). Is there is any way one can Read or write the control and status bits of the parallel port?

2). Can half of the data lines be used as inputs and the other half as outputs?

I have performed a write successfully and configured my port as bi directional from the BIOS settings.

Thanks.

[smercurio_fc]

Note: You did not mention your operating system, so I am assuming Windows... VISA has a limitation in reading from the parallel port due to a limitation in the Windows driver. You can read more here: http://digital.ni.com/public.nsf/allkb/B937AC4D8664E37886257206000551CB

[wond3rboy]

Hi, thanks for your reply. I have aleady gone through that document. I am using wondows XP. It shows the IN and OUT port as not available if i try to find it from LabVIEW help or from the functions palette itself. Just wanted to conform my notions whether they were correct or not.

[smercurio_fc]

They are available, just not from the functions palette or from the Help. Open the Example Finder (Help -> Find Examples) and search for "parallel". There's 2 examples, both of which use those VIs. Be aware that those functions are not compatible with Vista or later.

[wond3rboy]

Hi, sorry to reply so late. I did the In Port and Out Port writing thing. There is still one more thing remaining and that is of reading the parallel port using the VISA Read Vi. I cant seem to read the parallel port with it. It only gives me logic 0 on the read bits. I also set C5 to 1 so that i can perform the read (using the Out Port Vi),

[smercurio_fc]

As the document points out, how the parallel port works depends greatly on the manufacturer of the motherboard you're using, as well as the settings in the BIOS. You need to verify what you can and cannot do with the parallel port you have, and you need to check the settings in the BIOS.

Aside: If you're already using the In Port and Out Port VIs, why do you need to use VISA? What do you gain by mixing technologies?

[wond3rboy]

Hi Smercurio, i have set the parallel port as bidirectional from the BIOS. I am just getting 0's. Also about your point of doing it with the In Port and Out Port VIs, i am an instructor and hence need to show the flexibility/ease that LabVIEW provides with regard to interfacing hardware to my students. 

[smercurio_fc]

Well, I understand your objective and desire, but I can only tell you about reality. And the reality is that the KB article I pointed you to indicates that he OS doesn't provide the support that VISA needs in order to read the parallel port.