USB to parallel port converter

[NIquist]

It sounds like the VISA VIs are not communicating with your hardware as you expect.  If you have to wait for VISA write to timeout then that is a problem.

Have you tried using the register primitives to talk directly to your parallel port converter?  It may work better than VISA depending on the driver.  It's more low level coding though so it's more advanced.  Look at the "Parallel Port Read Write Loop" example VI and see if it can talk to your hardware.

Again, you may have no choice other than to buy a cheap DAQ.  The parallel port is slow and will not guarantee stable timing.  The USB-to-Parallel converter just makes things even more difficult.

[vijaysekar]

Hi nlquist

I just tried to connect 'USB to parallel port adapter' to stepper motor, because the I require only less than 5 Rpm.  For that my stepper motor would require 16 to 17 pulses per sec. Probably software timings will be  more than that. And I am going to give number of steps for my motor so that it will move to correct position.  Moreover  I think time fluctuation will not affect the accuracy because in stepper motor only the steps matters(since low speed application).   

As far as I concerned no one is successfully communicated to USB to parallel port adapters atleast to my level.  If we able to use as the parallel port it will be useful for all those who are having laptops. For them it would me mini DAQ because it has 8 digital lines.

It updates its ports more than 30 times per sec while I worked with that.  The problem was it works only when I use                                                     "run continuously button".

u mentioned about registry primitives right....?

I can't find any registry address because it is not detected as LPT in device manager.

What is the function of "set timeout" in the vi that I  have lastly posted.

[NIquist]

OK, for such a slow motion the parallel port should work fine.

The timeout sets the amount of time the VISA code will wait for a response from the hardware before it gives up and continues anyway. 

The code you started with really should work (as far as I can see).  Can you try it on a laptop or an older PC with a real parallel port?  I'm suspecting it's the USB-to-Parallel converter that's causing the problem.  I have to use USB-to-Serial adapters like that and they are almost always trouble to set up and then don't work reliably on every PC I connect them too.

[vijaysekar]

I have used that with my laptop .

I didnt use any wait time there will it cause problem.

And i didnt grounded pin 11 and 12 as mentioned in following address.  Is that a problem

here i have refered

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

[NIquist]

You must ground pins 11 and 12 to use VISA (otherwise it will hang up on you, just as you have experienced).  You don't need to if you use the Port I/O VIs.  (They will also give you more low-level control than VISA.)

Why don't you just try it and see what works best for you???

[vijaysekar]

Nlquist,

How to find out registry address. It is not detected as LPT in device manager.

I will try grounding pin 11 and 12 and run the vi. I will tell u the result also.

[vijaysekar]

nlquist

Same problem only arise after grounding pins 11 and 12.

Do u have any other vi which use visa to shift the values in parallel port. Because my program also may be wrong. 

usb to parallel port adapter is capable of updating its port more than 10 times per second( I observed it while running the program continously).

But i dont know why it is not funtioning as expected.

[NIquist]

I don't know how to determine a port address for a USB to Parallel converter.  You may have to contact the manufacturer.

VISA is a communication protocol that should work with all kinds of ports.  I can't think of anything else you could try except using a real parallel port and not your USB converter.  At least then you'll know if your code is working right.

[vijaysekar]

Hello Nlquist

Now I planned to use USB to serial port converter because, this will allow me to recognize it as COM port in MAX.

After that i am going to use serial to parallel converter to fulfil my needs.  I dont know wether it will work or not but, I am going to try that.

If u have any idea about that please tell me.

Thank you for all your kind answers.

[ejkaiser]

For a laptop I would recommend to use a PCMCIA parallel adapter. With those you can use the port functions and the port addresses hex378 and hex278.

Cheers

Edgar