I want to simply switch certain data pins on and off, so that they can control a set of relays. I'm not asking about the hardware bit (should be easy), but I don't know where to begin writing the software. I don't want a high level library that can send bytes to a device - I literally want to switch on/off certain pins.
I'm running Linux and I want to do this in Java, so would I just need a library? It would be nice if the library has good documentation and is easy to use, but if not then a short example code will help me get started.
There's a pretty easy-to-use API called ParalelPort:
http://www.oocities.com/Juanga69/parport/index.html?20112
Its very easy, you could use "write(int oneByte)", where in the "oneByte" you send a 8 bit word, turning on and off the pins you want, according to this diagram:
Bit | Pin # | Printer DATA
-----+-------+--------------
7 | 9 | DATA 7
6 | 8 | DATA 6
5 | 7 | DATA 5
4 | 6 | DATA 4
3 | 5 | DATA 3
2 | 4 | DATA 2
1 | 3 | DATA 1
0 | 2 | DATA 0