Date: Thu, 03 Feb 2005 10:26:59 -0600 From: Martin McCormick <martin@dc.cis.okstate.edu> To: freebsd-questions@freebsd.org Subject: /dev/ttyd0 as an Input Device Works on some Systems but not others. Message-ID: <200502031627.j13GQxx1022097@dc.cis.okstate.edu>
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I wrote a C program that opens /dev/ttyd0 for reading data from an external device. I had beginner's luck because it worked in Linux (actually that device is called /dev/ttyS0) and on the first FreeBSD box I tried it as /dev/ttyd0. The /etc/ttys file had /dev/ttyd0 set to off so there was no login banner and that system has been reading telephone switch logging data 24/7 for over 600 days. I then tried two different FreeBSD servers, each one with 2 serial ports and that's where I ran in to trouble. Here is what I notice. On systems like the one that is working, a test command like echo "hello" >/dev/ttyd0 works fine even if nothing is connected to the serial port. The port can be opened with /dev/ttyd0 as a file descripter and read indefinitely as long as an EOF char isn't received. On the two-port systems I have had trouble with, echoing anything to /dev/ttyd0 causes a total hang of that command that one can't break with anything short of a reboot. I have actually tried two single-port FreeBSD systems and both could read from ttyd0 and echoing output to ttyd0 worked as described. One of the systems is the one that has been up for 600 odd days. The BIOS settings on the two-port systems that won't work this way indicate that the port is on. The other choices are Auto and Off. Any ideas as to the reason for the differences and how I can make /dev/ttyd0 work the same way every time? The dmesg output describing the serial ports from one of the 2-port systems reads as follows: sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0 sio0: type 16550A sio1 at port 0x2f8-0x2ff irq 3 on isa0 sio1: type 16550A Any suggestions are appreciated. Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Division Network Operations Group
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