On Mon, 26 Jun 2000, Peter McAlpine wrote:

> Hi All,
> I have seen somewhere a circuit for how to connect standard
> 5v output ports to RS232 serial port of a PC using a couple
> of diodes... but  can't find it again.
>
> Anyone point me in the right direction please?

I just connect the PIC's xmit pin directly to the PC RxD, and the PC's TxD
to the PIC through a 22K resistor...  works fine for me.  You need to
invert the data, of course.  I've also seen a lot of different methods of
doing this with transistors, Zeners, etc. - I guess it just depends on how
close to "real" RS232C you want to get, but the drivers & receivers I have
looked at see anything below .7V as low and anything above 1.4V as high
(if I remember correctly), so TTL/CMOS levels work fine.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
                -- Isaac Asimov