Hi: I wrote a program for linux that drives the parallel port (hex 378). It works perfectly well. However, under XP, a little test program that writes the parallel port, in the same machine, written in Pascal, does not actually write it. The program consists of only one line: 'PORT[$378]:= $00;', so the probability of an error in the program is almost zero. In the BIOS setup menu, I have, in Advanced>Super I/O configuration>Parallel port address, three choices: Disabled, 378 and 278, of which I chose 378. Also, in the same submenu, Parallel port mode gives three choices: Normal, Bi-directional and ECP+EPP. I have tried the three of them but in vain.

True, in linux I used the instructions (C) setuid(0) and ioperm(0x378, 1, 1) while in Pascal I do not do anything like that. However, I think the O.S. should give me some error notification. But it doesn't. Could you tell how I cold solve this difficulty, without using another operating system?

Hi there,

of course, as you turned the wrong handles.

Now we're getting to the point. Both Windows and inux are operating systems that don't tolerate direct access to a certain piece of hardware unless explicitly granted. Your Linux program requests that privilege appropriately, your Windows program doesn't.

Yea. Windows is notorious for trying to invent something that might satisfy the programmer. In this case, it probably pretends to have done the port I/O operation.

As with Linux, a Windows program has to acquire the right to access a certain I/O port directly.

[X] Doc CPU

And how could I be granted access to the I/O space? In the Internet I learn about some Inpout32.dll for XP. It seems that it works transparently, as if the O.S. were MS-DOS. I'll try it and will post the results if it works. If not, I'll remove XP and install Win95 or DOS.

Hi there,

I used directio.dll in a project some years ago.

Yes and no. Yes means your application can indeed be given direct access to certain I/O addresses, and no, you have to ask for it first. IIRC, there's a function in directio.dll that you call and claim exclusive access to a range of I/O addresses, and on return, the OS says yes or no (of course, it still denies access to I/O addresses being used by drivers needed by the system itself, like HDD controller or things like that.

[X] Doc CPU

Thank you, sir. I'll try to get documentation on that directio.dll.

EDIT: I shall do it in Linux, given that I have already some experience driving the parallel port under that O.S. It is about programming the flash memory of a microcontroller device. Because the microcontroller firmware written by the programmer will later interact with a DOS-Windows program, it was more practical to do both things under the same O.S. But the successful programming of the part would be, in itself, a true achievement for me. So, more important than the operating system of choice, is I think, the fact that i have already solved the problegomena of interfacing with the parallel port in Linux.

If I wrote this post it is because I thought the thing would be easier.