Re: Real-Time Serial Problems

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Bert Hooyman (bert++at++demeern.sgi.com)
Sun, 08 Nov 1998 14:42:35 +0100

>I've been told by people in the business of building
>head-trackers that the Onyx systems only service
>the serial port at a 50Hz rate at best. This

If I'm correct, React/Pro 3.2 and beyond support a user-level mapped
interface to the serial ports, without the OS sitting in between. This
is on IRIX 6.5, Octane, Origin O2, Onyx2, only.

Serial Ports

IRIX 6.5 adds support for the user mode serial library, or usio, which
provides access to the system
serial ports on Origin, O2, and OCTANE systems, without the overhead of
system calls. On these
systems, the device /dev/ttyus* is mapped into the user process's
address space and is accessed directly
by the library routines. The user mode library provides read, write, and
error detection routines. In
addition to the library routines, ioctl support is provided to perform
functions that are not time
critical, such as port configuration. The read() and write() system
calls are not supported for this
device type, as these functions are implemented in the user library. For
complete information about
usio, see the usio(7) reference page.

On the Origin, O2, and OCTANE systems, support for a character-based
interface on the serial
ports is also provided as a low-cost alternative for applications
needing bulk data transfer with no
character interpretation, via the serial ports. For more information,
see the cserialio(7) reference
page.

-- 
Bert Hooyman,                  Coordinating Systems Engineer
Silicon Graphics b.v.,    Veldzigt 2a,   NL 3454 PW De Meern
phone +31-30-6696866, fax +31-30-6696899, voicemail 955-6866

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