glg@balrog.UUCP (Gary L. Grebus) (11/22/88)
Here's one for the hardware hackers...how hard would it be turn the
unix-pc 1200 baud modem into a serial port? Is there a separate serial
chip that could be hooked to the outside world, or is everything done by the
modem chip? Maybe the hard part of this would be kludging a the device
driver to run it.
A 1200 baud modem is getting less useful all the time.
/gary
Gary Grebus (K8LT), 16 North Mason Rd., Brookline, NH 03033-2452
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Ham Packet: K8LT @ KB4Nditto@cbmvax.UUCP (Michael "Ford" Ditto) (11/23/88)
In article <378@balrog.UUCP> glg@balrog.UUCP (Gary L. Grebus) writes: >Here's one for the hardware hackers...how hard would it be turn the >unix-pc 1200 baud modem into a serial port? I agree that the OBM is less useful than a serial port for most people, and it is quite feasible to bypass it and use its uart for a serial port. There are three problems that I can think of: 1) RS-232 Line driver & receiver would be needed (one IC). 2) There are no other RS-232 lines (DTR/CD/RTS/CTS). Even if there were, the driver would require modification to use them. I seem to remember that those pins off the 8274 are already used for the other port or something. 3) The driver won't set the speed to anything other than 300 or 1200 bps. I suspect, though, that the driver changes might turn out to be trivial since the desired code is already in there. It might be as simple as pointing a few vectors at the tty00[0-6] routines. -- -=] Ford [=- "The number of Unix installations (In Real Life: Mike Ditto) has grown to 10, with more expected." ford@kenobi.cts.com - The Unix Programmer's Manual, ...!sdcsvax!crash!elgar!ford 2nd Edition, June, 1972. ditto@cbmvax.commodore.com
jbm@uncle.UUCP (John B. Milton) (11/29/88)
In article <378@balrog.UUCP> glg@balrog.UUCP (Gary L. Grebus) writes: >Here's one for the hardware hackers...how hard would it be turn the >unix-pc 1200 baud modem into a serial port? Is there a separate serial >chip that could be hooked to the outside world, or is everything done by the >modem chip? Maybe the hard part of this would be kludging a the device >driver to run it. It should be relatively easy from the hardware point of view. The software is another matter entirely. The serial port for the modem is the other half of the NEC 7201 used for /dev/tty000. If you look at your major/minor numbers: 0 crw-rw-rw- 2 uucp mail 0, 0 Nov 28 21:34 /dev/tty000 0 crw-rw-rw- 2 uucp users 0, 2 Nov 27 20:00 /dev/tty001 0 crw-rw-rw- 2 root mail 0, 3 Nov 9 03:24 /dev/tty002 0 crw-rw-rw- 2 root users 0, 4 Jun 22 00:28 /dev/tty003 0 crw-rw-rw- 2 root users 0, 5 Jun 22 00:28 /dev/tty004 0 crw-rw-rw- 2 root users 0, 6 Jun 22 00:28 /dev/tty005 0 crw-rw-rw- 2 root users 0, 7 Jun 22 00:28 /dev/tty006 Your see that 0,1 is NOT used. Go ahead, make it. When you try to access it you will get a kernel panic. (odd address I think) The software is very nasty since the serial port is so buried in the phone driver. I could imagine a way to eaves drop the serial line during normal modem operation (for Tx Rx lights, for example), but not for generic serial port usage. John -- John Bly Milton IV, jbm@uncle.UUCP, n8emr!uncle!jbm@osu-cis.cis.ohio-state.edu (614) h:294-4823, w:459-7644; MS-DOS is a beautiful flower that smells bad!