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SubjectRe: Serial Port voltage drops with Linux
On Mon, Jan 17, 2000 at 10:48:14PM +0100, Juergen Hannappel wrote:
> Jens Benecke <> writes:
> > The situation is this: When we connect the hardware to the serial port,
> > the signal amplitude breaks down to lower than +3V (which is miniumum
> > for the PC to detect a "0"). With DOS, the signal amplitude varies from
> > -10..+10 V (approx) for 1/0 signals. With Linux, it's -10..<+3V, and
> > that is not enough.
> How is the power four your homemade hardware created, especially the
> positive voltage? Does it need special levels on the RTS line or
> something similar?

AFAIunderstood (I did not build the hardware) the RTS and DTR pins are
supposed to give the voltage required. There is an additional capacitor
(150uF) to keep the signals high enough, but we don't see anything on the
oscilloscope that accounts for the C.

I didn't build the hardware, I am CC'ing this to Guido who does the
programming and did all the experimenting, he should be able to explain it
a little better.

PS: Deutsch ist auch ok. Jedenfalls für mich :)

_ciao, Jens_______________________________
"[Microsoft] ... guarantees 99.8% NT uptime for certain hard-/software.
That's exactly the 3 minutes daily that my NT server needs to reboot."
-- ZDnet editorial

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