> Hang on a minute, polarity does not switch all of a sudden. The standard RS-232 interface chips include an inverter. The normal output from serial pins on microprocessors or PCI/USB serial chips expects that inversion.
For short runs where you are designing both ends, it's common to skip the RS-232 drivers. So if you are trying to talk to something like a GPSDO board without the typical 9 pin serial connector, there is a reasonable chance you may need to add an inverter. (or maybe a real RS-232 interface chip) -------- It's also possible to cheat on the RS-232 interface ship. A TTL/CMOS driver will work with most RS-232 receivers and a resistor with maybe a pair of diodes will protect a CMOS receiver from RS-232 levels. If you are doing that, you need an inverter in there someplace. With a microprocessor, the inverter is often available (for free) in the pad driver. -- These are my opinions. I hate spam. _______________________________________________ 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.
