i try to controll devices from parallel port by writing c program.but in port all ways 5v presents,i need help

Question

hi friends plz help me, i try to control electrical devices from pc's parallel port by writting c program.but in the parallel port all ways a constant +5v presents.even i try to sent data to the parallel port by using c program,there is nothing happened.there is no mistake in c program.i am using windows xp wit service pack 2.plese help me ,how to eleminate this +5v ,from my port

Answer 1

how are you measuring the 5v, and on what pin(s)? data will be represented by (about) 0v, and in an idle condition it will be 5v. if you are just using a volt meter you wont see it, you need to use an oscilloscope to capture the data.

Answer 2

it is harder than you think of. modern OSs block consumer mode classes from having direct hardware get admission to. You first want a kernel driving force that provide you the mandatory hardware get admission to. it is the case for the two Linux and homestead windows (and that i might suspect the comparable for MacOS). There are some widely used drivers that in basic terms divulge hardware get admission to to consumer mode classes, yet you may decide for to income the API for that driving force.

Answer 3

check out this site on parallel port programming
http://www.lvr.com/jansfaq.htm