[Umberto Zanghieri]'s ZP Engineering srl offers a 
LPTTCL extension [http://www.zpeng.com/projects_tcl_page.htm]
for parallel-port that works on Windows 98, NT, and 2000.


A few notes on LPTTCL by UZ.

    * parallel port access on Win98 is rather easy; on the other hand, doing the same on NT and 2000 requires a driver. LPTTCL attempts to provide the same technique on all three platforms.

    * it allows access not only to the data port, but also to control and status registers; this allows for many options (i.e., emulation of EPP cycle access)

    * it is not speed optimized; bit-by-bit control is rather slow.

    * it has been designed for simple control of external devices and emulation of serial protocols as I2C.

Users have reported that it works correctly under Windows XP.

A few additional notes (UZ, 29 aug 03):

    * LPTTCL must be installed and run by a user with administrator privileges

    * uninstall must be done manually, by deleting the files and by removing the following entry from the registry: 
HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\SERVICES\ZPPORT.

    * LPTTCL only works for low-range I/O (ISA style). If you have a PCI parallel port card that maps into a high I/O, you will not be able to access it from LPTTCL.

    * we received feedback from many users that use it for access to custom hardware, development boards and similar. Someone has used it for PLD download, others for I2C bit-bang emulation, others for adding pushbuttons to a PC...


[[Many other references.]]

[[Basic applicable technique is to open the port (by name) and write to it.]]

=)



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On Linux (or any other PC Unix) just open the right device (''/dev/???'') and then read and write it as you wish for basic access.
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[Serial port] programming is of related interest.