-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi
> So is there anything terribly bad/spec-violating/unsafe about driving > an always-asserted RS-232 output directly from the +12V supply through a > resistor, or is that perfectly OK? What should the resistor value be? > Or should I use something more fancy like a PTC resistor acting as a > resettable fuse protecting against external shorts? I currently have a circuit in front of me that uses PNP transistors as switches to connect a supply voltage directly to the TX line of a RS-232 output. I believe this is pretty much identical to shorting that line to supply voltage. So I would say that it would also be safe to directly drive lines in your case. I've also once seen 4.7k resistors in series with RS-232 lines. It is probably a good idea to limit the current that way in case of a short circuit. I can't say if that violates any standards. I certainly wouldn't bet on the manufacturer of this board to stick to specs if it that meant saving a few components :) Best regards Tomaz -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFFbgHYsAlAlRhL9q8RApB+AKDN5so+IkH0gKhsRgsXS4nEJ8o2+wCfaVDM qpGX7mxUMoZ2p7884XZfhMs= =FLX4 -----END PGP SIGNATURE----- _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user