how to talk to the serial and parallel ports through a C

[Olivier Nicole]

I'll reply on the parallel port:

fd_relay=open("/dev/ppi0", O_WRONLY);
ioctl(fd_relay, PPISDATA, value)

Value being an 8 bits value.

That works wonders with the relay card from Quality Kits
http://www.qkits.com/serv/qkits/diy/pages/QK74.asp

As for the entry, as I only needed 2 contacts, I used mouse button
(plus it provides a nice testing interface, just click on your mouse
buttons :)

Olivier