Hi, I am into new project, which should use microcontroller. The easiest way to program it is using parallel port. But, there are few things I hope you can help me with. Oh, and the preferred language is C and platform Windows.
So, I studied LPT ports and Windows a bit, and from what I learned the most important is: Since Windows NT based systems, you cannot use instructions for direct port manipulation. This should be, because now programs are run in different privilege mode, which doesn't support the kind of instructions that are used by outport() function.
But at this point, I don´t understand a few things. First, I thought that Windows actually used privilege levels since first protected mode version, but that's the wrong assumption.
But more importantly, I thought that Windows has included functions for just about any hardware communication. I mean, anything you do in Windows these days, you just call windows functions which further call kernel services. I assumed that outport() doesn´t use any Windows function, and just makes the communication itself, which is prohibited now. But I am literally shocked that there is no system function to control parallel ports in modern Windows systems. At least that's what I read.
But even if I could get the control of parallel port, there comes my second problem. For programming the controller, I need to follow special protocol, especially timing. But since Windows is multitasked, I worry about what if Scheduler switches to another app, and therefore when is the right time to switch signals on LPT, my program just will not be able to run.
Oh, by the way, I know I could use any 3rd-party apps, but I just like to be able to do it myself, or at least before I use some 3rd-party app, I want to know how it works. And yes, you can program some microcontrollers just by parallel port with some resistors, I know this for sure.
Thanks.