Re: [uCsimm] new subscriber

From: Larry Doolittle (
Date: Thu Mar 29 2001 - 17:56:56 EST

On Thu, Mar 29, 2001 at 10:47:51PM +0100, Ian Leonard wrote:
> > If I'm not mistaken, the RS 232 interface requires plus and minus
> > voltages between 5vdc and 12vdc. The regulator included in the kit
> > mention above I believe is only a positive linear regulator. How is the
> > negative voltage achieved? (From the Linux workstation RS232 port plus &
> > minus pins?))
> Don't know, but it works. I just do the software. I could ask the hardware
> guy here, but then I would have to admit that I don't really know what's
> going on.

Lineo presumably uses an RS-232 driver that develops the
needed voltages internally from 5V (or 3.3V) power.
The breakthrough IC was the Maxim MAX232
but there are a zillion choices now.

      - Larry Doolittle <>
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