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From: Tilmann Reh
Subject: Re: Line-powered EIA-232 interface
Date: Sat, 14 Dec 2002 21:46:17 +0100
Organization: Autometer GmbH
NNTP-Posting-Date: 14 Dec 2002 20:44:55 GMT
X-Mailer: Mozilla 4.78 [de] (Windows NT 5.0; U)
> I have a low power microcontroller running from a 3V Li battery.
> Want to interface it to a (laptop) PC's EIA-232 interface.
> I'm aware of the DS275, which was designed for this purpose, but it needs a
> 5V power supply. I thought I could get a + and - 10V from the PC, but when I
> checked I only measured the -10V on an idle connection.
> Any ideaz? (may be with discrete components, but should tax the battery as
> little as possible; the battery should last several years).
If you don't need the handshake lines you might program them to be
constantly active while the according PC program is running.
Then there will be about +8 to 10 volts, with enough power to
supply a lowest-power transceiver.
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
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