Real time ports under windows

[alzomor]

Hi

Is it possible to use any of the PC ports (serial , Parallel or USB) to send data in gurenteed time frame under Windows OS?

Salam
Hossam Alzomor
www.i-g.org

 

[jhbbunch]

No. Windows is a preemptive multitasking enviroment. Your program can be preempted at anytime. Intensive Hard Drive accesses - reads and writes - can cause your program to be held off the processor for 10's of milliseconds. Realtime control, like motion control is always done with dedicated boards.. That being said, I've run steppers with good accuracy off of the parallel port. If your needs aren't critical, port control with Windows may suffice, but if you need microsecond accuracy, you need dedicated hardware.

 

[alitavakol]

some usb chips like cypress and ftdi ones support isochronous and interrupt transfers. Isochronous transfer has accurate timing, and windows accepts timing concepts related to this type of transfer. Interrupt transfer has a maximum latency.

but ftdi didn't supply isochronous device driver, and you should write it yourself (a very confusing and time consuming task).
cypress supplies this and many books and tutorials on usb also work with cypress chips.