Hi all,

What is the general opinion concerning the use of a proper RS232 driver IC
using 'proper' RS232 levels (+/-10V whatever) , such as the MAX232 or
equivalent, as opposed to using 5V levels, so that a simple buffer - or even
a direct connection to PIC's I/O pins could be used?

I understand why the MAX232 exists as it does and the importance of using
such a device if the RS232 connection is to be made over a fair distance, to
ensure compatibility, ESD protection (presumably!), and in order to work
with the sort of loads that may be 'seen' at either end of the connection.
As far as I understand (though I'm sure there will never be a simple answer
to this!) many PC I/O ports nowadays are down to 0 and 5V (or maybe -5 / 5V,
please correct me if I'm wrong) and apparently it's a good idea to assume
these levels could do right down to +/- 3V. Can of worms, maybe? :o)

I have an application which requires an RS232 connection. I'm only making
one of these things. I know that really I could just bung in the MAX232 and
forget about it, though I'm just curious as to what approach others might
take here. It's a unit which transmits IR messages corresponding to commands
sent from the PC serial port. For the hell of it I'm wondering if I could
power the unit straight off the serial port, maybe if I omit the MAX device
and pulse the IRED at a fairly low current (only a short distance needed
here).

I've been reading the text at this link:

http://www.hut.fi/Misc/Electronics/circuits/rspower.html

which has been extremely helpful. Though I'm still not sure. Any thoughts
anyone?

Really my main question here is - if I'm designing a little circuit that
draws a significant (but acceptable) amount of current from the serial IO
lines, and the connection distance is small, are there good reasons for or
against using a '232 or similar driver IC?

Kind regards,

Trevor.





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