> You are right ;) You can also use a spare analog op-amp or comparator to
> boost RS232 in the other direction.
>
> Peter

Depending on the situation, you can also send it just using the PIC
itself, and invert the output logic level. Not something I'd reccomend
for industrial environments, but it works. The common 232 receivers
don't need negative voltage, just <1V, and they need at least 3V on the
high side.

On the RX side, a resistor in series with the incoming signal, and a
pair of diodes at the pin to +5V and Gnd will clip off the negative side
and limit the current, then the pic can decode it. Again, the polarity
is inverted, but that's a fast hack.