Hi Brian, That's just strange. There are a whole lot of these MAX232 and MAX3232 devices being sold. Hmm, I'm looking at the UT+ User's Guide, and it lists the voltage levels as follows. These would imply that an inverter is necessary, right? Could it be that someone programmed your PIC upside down - i.e. using negative logic?
TTL 0 V to 0.8 V = logic 0 2.4 V to 5.0 V = logic 1 RS-232 (reordered from manual to put logic 0 on top) 5 V to 15 V = logic 0 -5 V to -15 V = logic 1 Bob - AE6RV >________________________________ > From: Brian Alsop <[email protected]> >To: Bob Stewart <[email protected]>; Discussion of precise time and frequency >measurement <[email protected]> >Sent: Friday, July 12, 2013 9:09 PM >Subject: Re: [time-nuts] GPDSO is working > > >Hi Bob, > >Here is my experience. I had a PIC that output RS232 at 0-5 volt >levels. It actually worked with my computer directly. When I added a >MAX 232 to make the levels something like -10/+10 volts. It didn't >work. That's because the MAX232 inverts the polarity. Look at the data >sheet, the level converters are clearly inverters. > >The fix in my case was to invert the RS232 stream output by the PIC and >all was fine. > >I'm not sure exactly what you have but a scope sorts it out quickly. > >73 de Brian/K3KO > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
