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reading from parallel port
Hi,
I'm trying to reuse 'short' sample driver found in ldd2 that handles
read/write on parallel port for my small app.
I've connected opto encoder to two status pins (select and paperOUT) on
lpt port. With small & dumb userland app I'm able to select() and read()
value from status port by opening /dev/short1 and reading one byte. What
happens is that select() returns immediately giving me status register
contents as fast as it can, producing big overhead. What I would like to
see is that select() returns _only_ upon register content change
(impacted by turning encoder knob).
Doing this kind of checking in userland hogs my cpu on 100%, so I guess
solution lies in my drivers read() function.
Is this doable by simply checking new read value against one just read,
and ignoring it if its the same, or is there some other
mechanism/procedure that can be used?
thanx,
h
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hinko <dot> kocevar <at> iskramedical <dot> si
Hinko Kocevar, developer
Iskra Medical d.o.o., Stegne 23, 1k LJ, SLO-EU
"AÃ rÃn" | [Analects XII:22]
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