At 9:34 AM -0700 10/13/97, Mattias Engstrvm wrote:
>I'm wondering if there is an easy way to convert RS232 output to levels
>suitable for
>a PIC. Like perhaps stripping the negative voltage with a diode and
>running the remainder through a transistor or something?
>
>Any pointers would be helpful.
>
>Regards, Mattias Engstrom
>
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Place a 100K resistor in-line with the RS-232 signal of interest. The internal
clamping diodes will shunt the excess + voltage to VCC and the excess -
voltage to VSS (ground). Make sure you connect the RS-232 GROUND to
your VSS. Otherwise, you can get random results if you get anything at all.
(Classic example is it working great when looking at it with a scope probe!)

If you want to be extra careful, you can place a 100K series resistor on the
RS-232 ground connection.

cheers,
eric