How to make virtual parallel port for Windows applications?

[kot_b]

USB-parallel

Hi!
There are a lot of USB-RS232 converters, and there are no problemm to make electrical interface for USB-PARALEL, but how to make virtual paralel port, wich will be visible for windows applications?

 

[ntfreak]

Re: USB-parallel

I am not aware of a driver already done, it looks like make your own.
Have a look at **broken link removed**
this is source code to a virtual comm port to irda, might get you started

Regards
NTFreak

 

[Big Boy]

Re: USB-parallel

There may be a solution for you. There is actually some USB modules out there that use a chip made by FTDI. It's a module with USB to parallel converter. You connect the module on your board, it give you 8 bit bi-di data lines, plus a few controls (read, write, tx buffer full, rx data ready).

FTDI also provide free USB drivers on their web site. After installation (which may be a bit tricky), you have a standard 'c' header file and dll that give you access to the module.

There are two drivers, one that act like a fast COM port (work like any other COM port, programing-wize), and one parallel driver. The parallel driver is a bit more complex but give you more flexibility. You can only install one of the two drivers, and switching between drivers can be a pain, especially on XP.

Basically, you just send data with a function, and the data bits come out of the interface. You put data on the interface, and by calling a 'c' function, you read the data byte.

This interface have some limitations though. It is best suited for micro-controler applications. It's not really like a standard parallel port which you control each pins, you really have to 'read' and 'write' the bytes, using control lines.

Also take note that USB does have much higher lattency than parallel port. Meening that where you can set a register to one or zero and see the corresponding pins go to 5V or 0V almost instantaneously on a parallel port, on USB, the data can take a millisecond to get to the other end. So USB is really more suited for 'packets' of data. Applications that need to send only a few bytes, wait for response, send another byte, wait for response, ... are really not for USB.

Just do a search for 'usb module' and 'ftdi' in google.

Big Boy