Date: 27 Mar 2000 01:25:53 +0200 From: naddy@mips.rhein-neckar.de (Christian Weisgerber) To: freebsd-questions@freebsd.org Subject: Re: dumb terminal on db9 serial port Message-ID: <8bm6a1$94n$1@bigeye.rhein-neckar.de> References: <38DD5024.E7E2958C@cam.org> <8blbha$1cka$1@bigeye.rhein-neckar.de> <38DE871E.44B97FC4@gorean.org>
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Doug Barton <Doug@gorean.org> wrote: > > I think BSD expects DCD to be active. A local bridge DTR->DCD should > > do. The terminal also may require DCD to be active. > > I'm coming into this late, so pardon me if I'm off base here. If you're > trying to set up a standard serial terminal for freebsd all you need are > Tx, Rx (crossed of course) and SG. That is the very minimal configuration. If the terminal supports hardware flow control (not all do) you really want to wire up those leads and use them rather than dealing with XON/XOFF or setting the speed so slow that flow control is never required. Also, your three-wire setup leaves various control lines floating at undefined levels, which isn't that great. I know that OpenBSD requires DCD to be active for a terminal, because not all that long ago I connected a VT220 to a OpenBSD box. I'm fairly certain the same holds true for FreeBSD, but I don't really remember for sure. > In a standard null modem cable you would connect CTS to > RTS, and DTR to DSR, not the way you have it here. We're not dealing with a standard null modem cable (a somewhat ill-defined term) here. We're talking about connecting a terminal. A good many terminals support DTR/DSR flow control in a fashion equivalent to the way RTS/CTS is used on PC serial ports for this purpose, in which case wiring up a cable with DTR-CTS and DSR-RTS is just the right thing to do. I have been using this for my VT320-clone. I don't know what types of flow control a Wyse 60 supports. The truth is, serial ports are a mess. The semantics of the various control lines are ill-defined and in practice their actual usage varies with the hardware. Connecting a terminal is fairly easy if you have some experience but can turn very painful if you're trying to work by recipe and don't understand what you are doing. When you deal with an unknown terminal, you don't start by soldering up a cable. You grab your serial kit with break-out boxes for LED displays and arbitrary jumpering of the leads. Starting out from educated guesses or the manual and progressing by trial-and-error you refine the configuration until everything works. *Then* you make an appropriate cable. Well, that's my approach at least, and I don't have anybody to turn to for help. -- Christian "naddy" Weisgerber naddy@mips.rhein-neckar.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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