Parallel Port Interface

[Krakerjak]

Does anybody use/have one of these???
I'm planning on building my own for home use but I don't have the best resources on information on the topic.
Google ruturns a bunch of crap.

I have schematic a of one that i used in my lab but it is quite vague in some areas, such as traces....
The grey circles would be capacitors and im not quite sure what the large grey rectangle is on the upper left side.....


I also dont quite understand why all of these ic's are needed such as all the inverters and the opto-couplers....
there are 10 LS/HC04 inverter chips, totalling 60 possible inverter gates ....odd


I have looked at some crappy designs online but they arent quite what i'm looking for and some just have bad design.
I found one that was using the more expensive tristate inverting/noninverting buffer diivers but the schamatic showed that all the buffers were inverted and always enabled making the third state a very useless feature.

 

[blahblah99]

Those inverters/buffers/tri state chips are there to protect your parallel port in the event that two pins accidently get shorted after the buffers. In that case, the buffers would fry up and leave your parallel port protected. You can just use the parallel port without those devices, but it'd be dangerous for your mb.

 

[muttley]

the optic isolators are nice also.

 

[GermyBoy]

If you really want to do something like this, go to the store and start buying a bunch of $5 parallel port PCI cards. That way when (and I say when because you WILL ruin at least one) you fry the card, your mobo doesn't die. When you fry your parallel port on the mobo, quite often, the mobo likes to die, as no two pins like to have more than 20mA go through them.

Peace,
GermyBoy