a MAX232 will do a logic inversion. You either need to use another inverter between the PIC and the MAX232 or change the pic code to invert the signals.
Larry G Nelson Sr.

> 
> From: "Mark Chauvin" <chauvin555@sbcglobal.net>
> Date: 2005/10/06 Thu AM 07:32:04 EDT
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Subject: [PIC] Serial pins to MAX232
> 
> I've got a design that someone else gave me, for a PIC16C58B.  It has the 
> rs232 serial lines from the db9 connector coming in PIC pins 1 & 2. 
> Transmit from the DB9 goes thru a 33k ohm resistor to PIC pin 1, and DB9 
> receive is tied directly to PIC pin 2.  DB9 pin 5 is tied to ground.  Comm 
> is 19200 baud, no handshaking (3 wires only).  I'd like to add a max232 chip 
> to the design.  I've got a max232 chip wired up to it, but can't get it to 
> work.  The guy that sells me the (pre-programmed) PIC's says the PIC serial 
> pins "are of oppposite logic levels" so the max232 won't work with it.  I've 
> got the chip wired up similar to what's shown here:
> 
> http://www.boondog.com/tutorials/pic16F84/rs232x.gif
> 
> except I have C9 tied to gnd, not VCC.  What am I doing wrong, or will this 
> even work without modding the PIC itself?
> 
> Thanks
> -Mark
> 
> 
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