Re: [aclug-L] Info Request

[Steven Saner <ssaner@xxxxxxxxxxxxx>]

On Wed, Sep 16, 1998 at 02:44:24PM -0500, John Goerzen wrote:
> Jeremy S Johnstone <jsjohnst@xxxxxxxxxxx> writes:
> 
> > NONNONON.... do not put +/- 5 Volts to the serial port
> > 
> > Use a transistor to raise the logically states up / down. If anyone needs
> > schematics just say so.
> 
> Well I wasn't saying one should send voltage to the port, I was saying 
> to read from the port, as I've read of people hooking up simple on/off 
> switches this way.  Or was what I said about reading from the port
> wrong as well?  It's been a long time since I've dealt with them at
> such a level so I defer to your knowledge on this.
> 
> 

This is more electronics than Linux, but since someone else started it...

The RS-232 standard is +5 to +15 volts for output logic 1 and -5 to
-15 volts for output logic 0. Input voltages are +/- 3 to 15 volts
respectively. I would use a chip that is designed to convert the
RS-232 signal to standard TTL logic levels such as the Motorola MC1488 and
MC1489 or equivalent. It makes the interfacing easier.


-- 
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Steven Saner                            SouthWind Internet Access, Inc.
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