Brian Foster wrote:
> I'm running SUSE 9.2 and, for various not-relevant
> reasons, decided to run the YaST2 init(8) “runlevel”
> editor. it hung during its initialisation. after
> investigating, I determined the bash(1) command:
>> isserial </dev/ttyS1
>> is hanging; strace(1) shows the (bash) open(2) of
> /dev/ttyS1 is hanging. this isn't too surprising
> since ttyS1 is the serial modem (and all this was
> done whilst I was off-line; i.e., that serial port
> is NOT open, and there is probably no other process
> trying to open it (and the permissions are not the
>> after a few false starts, I determined the hang is
> because the line has _somehow_ been configured to
> require various modem-control signals (i.e., it's
> not a simple 3-wire connection). again, not too
> surprising (albeit it took me awhile to get to
> this “obvious” point! ;-\ ). the (admittedly
> unused) non-modem serial port is not so configured.
>> but at this point I'm stuck: how does Linux (2.6)
> configure a serial port to use (or to not use?)
> modem-control signals? this is (now) just for my
> own curiosity since the original YaST2 problem can
> be solved by a bit of hacking on the relevant shell
> script. I've _no_ intention of changing anything
> w.r.t. the modem or the serial port; I am (now)
> simply curious.
>> ( apologies if this is described someplace; I've
> drawn a blank with quick searches for an answer.
> nor did I spot anything in /etc/init.d/*, albeit
> it's always possible I missed something? .... )
>There seem to be about 3 incompatible ways of doing this. I remember
last year figuring this for a PIC based LCD + keypad I programmed as a
terminal connected to serial port. I wanted keypress level interactive.
The various examples on net about handshanking and how to disable CR
input buffer AND have my Linux C programming skip char i/p if no key
I'm using two serial programs currently, one does the Xmodem to my
latest developemtn board and the other handles screen / terminal
formatting properly. (KDE). Minicom does handshake, Xmodem & formating,
but only with a modem. I set worong serial port and now it exits with error.
Presumably there is a Linux KDE equivalent to MS Hyperterminal for
serial, that is free and actually does what I want, but I don;t know
what it is.
Additonally there are three schemes for RS232 hardware handshake wiring,
using one or two or both schemes of HW signalling,. A Modem can use two
of them at same time, a Terminal or inter PC only needs either of those
two, and some serial printers have used a third wiring scheme. Oridinary
modems never use Xon/Xoff SW handshake.
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