kern/153289: Modem Ring Signal not reliably detected
sonilg at utstat.toronto.edu
Sun Dec 19 02:10:10 UTC 2010
>Synopsis: Modem Ring Signal not reliably detected
>Arrival-Date: Sun Dec 19 02:10:09 UTC 2010
>Originator: Tom Glinos
U. of Toronto
FreeBSD atlas.jarnac.org 8.1-RELEASE FreeBSD 8.1-RELEASE #0: Mon Jul 19 02:55:53 UTC 2010 root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
Modem Ring Signal not reliably detected.
On the hardware side, create a switch that toggles DTR to RI. Also DTR to DSR.
On the software side, run a program to repeatedly scan the modem status register with a TIOCMGET ioctl
A toggle of DTR to DSR is always detected. A toggle of DTR to RI is less than half the time detected. Tested against two different serial hardware, similar behaviour.
The same code with same/similar hardware runs perfectly under LINUX.
Unknown at present. There are plenty of work arounds like changing the harware or OS but anyone still using a modem should be seeing this problem.
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