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paralel port - doesn't keep pins states

DISCUSSION filip 2 participants 2 messages Apr 6, 2003 – Apr 15, 2003

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filip

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#0 lore raw

Hello,

I hope it is the right place to ask about my problem...

I want to use /dev/lp0 (lp module) on my PC for controlling external devices.
The problem is when I wtire 1 byte to /dev/lp0, paralel port keeps this state just for few ms...
(I made special plug - so the is no problem with handshake - details on:
http://www.hut.fi/Misc/Electronics/circuits/nullprint.html)

It is strange because everything works corect on my old PC (Pentium160).

Regards,
Filip

#1 lore raw
Quoted 12 lines · filip

Hello,

I hope it is the right place to ask about my problem...

I want to use /dev/lp0 (lp module) on my PC for controlling external devices.
The problem is when I wtire 1 byte to /dev/lp0, paralel port keeps this state just for few ms...
(I made special plug - so the is no problem with handshake - details on:
http://www.hut.fi/Misc/Electronics/circuits/nullprint.html)

It's normal, since the parallel -port specification clearly states that the port doesn't maintain the pins voltage more than a minimum mandatory delay, and while setting, the state is undefined.

Quoted 2 lines

It is strange because everything works corect on my old PC (Pentium160).

That was broken hardware, it didn't meet the specifications :))

Quoted 12 lines

Regards,
Filip
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