Bob Blick <bblick <at> sonic.net> writes:

> But if you currently have a situation where the transistor is normally on,
> you might be able to flip things around - use a resistor for the normal
> part, and use a PNP transistor instead. This works fine in most RS232
> buffer situations.

Wouldn't a PNP cause the same problem as a NPN darlington ? When the PIC pulls
the base to GND the transistor is still open and it pulls C to E which is at
+0.6V. This is imho a little close to the 'standard' threshold of a RS232
receiver. A Darlington would have the same problem.

Peter


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