On Sun, 19 Sep 1999 16:54:51 +0100 Dan Rosenfeld writes: > I'm also > wondering > whether I can get away with running this all at Vdd = 3.0V (thus the > LF84) > or will I need run at some higher voltage while debugging. You can make a direct connection if the PC is going to accept the 0 to 3V signal. I haven't tried but I suspect that many will. If you don't use a level converter the PIC software needs to send out bits of opposite polarity than if a level converter is used. The serial out line of the PIC should idle near Vss for a direct connection. With a level converter it would idle near Vdd, the level converter will convert that to a negative voltage for the RS-232 line. If your PC doesn't work with such a small voltage signal it would probably be better to include a level converter circuit in the PC adapter circuit rather than increase the PIC supply voltage. The PIC circuit would then be unchanged for debugging other than tapping off a 0 to 3V logic line for serial output. > I'm pretty clear on the PC side (terminal emulator app or basic > program), > but I'm not certain of the exact electrical connections on the pic > side. > I've seen mention of using anywhere from 1k to 1meg in series w/o > tx/rx > lines and along with some mention of pulldowns on these lines. If you are transmitting only from the PIC no resistors are necessary. It may be a good idea to use a small resistor (100 ohms) in series with the data line to limit current in case of a fault. So you'd connect PIC ground to PC ground and PIC pin (possibly through resistor) to PC data in. > > Also, do I need to do anything special with any of the other rs-232 > lines > such as RTS/DTS, etc. or can I just let them float? (Assuming the pc > software is configured correctly.) Most PC software will can be set to ignore the handshaking lines, but some would like them driven high. A conventional way to do that is connect CTS to RTS and DSR to DTR at the PC connector. The PIC circuit would just connect to two pins: ground and data in. ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.