On 07/09/06, Woodchuck <[EMAIL PROTECTED]> wrote: > > On Wed, 6 Sep 2006, Edd Barrett wrote: > > > > If it works with the sun box, I assumed it's the correct cable? > > Not necessarily the case, said the grey old admin, sighing and > wincing with the facial tic he thought he had lost in the mid 1990's. > > Getting a serial terminal to work is one of the bitchier bits of > olde-tyme sysadmin work. (It is not as bad as getting a serial > printer to work.) Google for "null modem pinout" and you should > get a sample of the sort of witchcraft to which desperate admins > have had recourse over the decades. > > There are different kinds of null modem cable, varying by mfg and > "philosophy". Null modems were at one time a seductive sink for > the sort of creativity that now is reserved for quirky software > license schemes and object-oriented programming. An RS-232 cable > can have, alas, 25 lines. Since only 7 (2 data, 1 gnd, 4 control > (2*(I'm busy, I'm alive))) are useful in any *practical* sense, the > other 18 (as well as the 4 "useful" control lines) can be combined > in a variety of intriguing ways to achieve or suppress some obscure > feature. This includes crossing-over, looping back, joining together, > and hard-wiring to ground or to certain voltages. Sometimes a tiny > resistor or capacitor might find its way under the shield of the > cable, cunningly soldered across the backs of two pins.
This sounds really fun. :\ DEC cables usually work between DEC terminals and DEC computers. > Sometimes DEC cables work between genuine DEC terminals and PeeCees. > Hooking up an IBM terminal (even emulating (often this means > "mocking") a vt100 or vt220 -- this emulation may not extend to the > finicky hardware parts) to a Sun with a Sun (?) cable, experiencing > the rare joy of "working terminal" does not completely predict > behavior of that same terminal and cable with a PeeCee. Some sly > manufacturers may have stooped so low as to create "console" ports that > require a "straight" cable; Sun? I should look into that. this is where "philosophy" can rear > its head. PeeCees don't do that, at least the "standard" (har-har) > ports don't. > > Try setting "local" in /etc/ttys. How you make that IBM terminal > give up trying to set/read various control lines I don't know. > > Before you throw in the towel, try a simple 3-conductor null modem > cable, simply carrying through signal ground and swapping the two > data lines, in conjunction with "local" in /etc/ttys. After that > barely works, you will have to figure out how to set XON-XOFF flow > control with stty maybe. Some of this junk can be set with tset, > too. yikes. ok Dave "My VT-101 works and I'm not touching it again." > -- > Experience runs an expensive school, but fools will learn in no other. > -- Benjamin Franklin Thanks for your comprehensive and amusing reply! Best Regards Edd
