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List:       gpsd-users
Subject:    [Gpsd-users] Mac OS X & BSD - Should we use /dev/tty.xxx or /dev/cu.xxx for gpsd?
From:       frank () nicholasfamilycentral ! com (Frank Nicholas)
Date:       2005-04-09 14:23:32
Message-ID: 5dcb7d2f29a72ebe33b7303e8d900e5a () nicholasfamilycentral ! com
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I've been investigating some oddities with Bluetooth serial ports on 
Mac OS X, and wondered what the difference was between /dev/tty.xxx 
devices & /dev/cu.xxx devices.  I found the following paragraph:

"The idea is to supplement software in sharing a line between incoming
and outgoing calls.  The callin device (typically /dev/tty*) is used
for incoming traffic.  Any process trying to open it blocks within the
open() call as long as DCD is not asserted by hardware (i.e. as long
as the modem doesn't have a carrier).  During this, the callout device
(typically /dev/cu* -- cu stands for "calling unit") can be freely
used.  Opening /dev/cu* doesn't require DCD to be asserted and
succeeds immediately.  Once succeeded, the blocked open() on the
callin device will be suspended, and cannot even complete when DCD is
raised, until the cu device is closed again.

That way, you can have a getty listening on /dev/tty*, and can still
use /dev/cu* without restrictions."

This leads me to believe I should be using /dev/cu.xxx devices.  Anyone 
know more about BSD/Mac OS X serial devices, that can make a 
recommendation?

I've been investigating some oddities with Bluetooth serial ports on
Mac OS X, and wondered what the difference was between /dev/tty.xxx
devices & /dev/cu.xxx devices.  I found the following paragraph:


"<fontfamily><param>Courier</param><x-tad-smaller>The idea is to
supplement software in sharing a line between incoming

and outgoing calls.  The callin device (typically /dev/tty*) is used

for incoming traffic.  Any process trying to open it blocks within the

open() call as long as DCD is not asserted by hardware (i.e. as long

as the modem doesn't have a carrier).  During this, the callout device

(typically /dev/cu* -- cu stands for "calling unit") can be freely

used.  Opening /dev/cu* doesn't require DCD to be asserted and

succeeds immediately.  Once succeeded, the blocked open() on the

callin device will be suspended, and cannot even complete when DCD is

raised, until the cu device is closed again.


That way, you can have a getty listening on /dev/tty*, and can still

use /dev/cu* without restrictions."</x-tad-smaller></fontfamily>


This leads me to believe I should be using /dev/cu.xxx devices. 
Anyone know more about BSD/Mac OS X serial devices, that can make a
recommendation?

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