Hello John, You can do what you want however, you will need to create a program, a dll, or an ocx in a lower level language than VFP. Once you have one of the latter you could use VFP to control your device.
What you will need to do is get a pinout of the desired I/O port the rs232 port (we call that a comm or mouse port) could be a very good candidate. Or if you are looking to the future you could use a USB or a 1394(fire wire) port on newer computers. The USB or firewire answers may be an excessive answer it will however, allow for the maximum growth with firewire being the greater of the two. The parallel port may not provide you with the ease you are looking for BUT if you will ultimately be looking for very fast TWO WAY communications this or the USB would be a viable answer. One mor ething about USB and 1394 is that they are hot swapable. That is they can be connected and removed while the computer is operating.
IMHO, you need to explore these avenues, define your ULTIMATE goal and make a decision based on that rather than initial ease. You will have to look at available voltages and insure that the signal comming from the computer is a sufficient breakover voltage to trigger a state change. Almost all of these devices are real time so if you write your program to operate in real time You will get your timing issues resolved very quickly. I think you should explore using C++ as you can access the computers lower functions at a relativly high level and still use some block ASM if you need it.
As yet another aside, :) I would just mount a connector to your board to ease the connection and disconnection process. 5 meter max USB 4.5 meter max 1394.
I hope I havent over informed you. :) I think that all of the info you will need to get started will be found in the following places:

Technical specs for rs232 can be found here:
http://www.ctips.com/rs232.html

Technical specs for parallel(db 25) can be found here:
http://www.ctips.com/para.html

Technical spec for USB can be found here:
http://developer.intel.com/design/usb

Technical specs for IEEE-1394(firewire) can be found here:
http://www.adaptec.com/technology/standards/1394bus.html




>Hi,
>
>I need some advice on how to communicate and control a stepper or servo motor through VB of VFP.
>
>Are there any Activex controls which I may purchase from a third party customer that will allow me to acheive this?
>
>Do I need any interface cards, or can I send signals directly through a parallel and/or serial port to to be used as a clock signal for a counter IC (Integrated Circuit)? The second method is the preferred method.
>
>I would also like to control the frequency of this pulse signal.
>
>Again, I need a simple solution, which does not require the need to buy expensive hardware and software. Presently I have the stepper motor, and a board for the phase sequencing, which does not plug into a computer slot or any controller. I need to simply send pulses directly to the board using only my serial and/or parallel port, which will be connected to this board via cable, whih in turn connects to the motor.
>
>If this doable, do I need to boost the signal coming from the computer, or is the signal strong enough as is.
>
> I am consulting a manufacturing company, and this is the project I have accepted. Personally, I do not have much experience with this. so any advice is strongly appreciated.
>
>Thank you very much.
>
>John Vlahos