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| HowTo Linux Zone | Linux Zone Home | E-Mail Me | Linux IR HOWTO Werner Heuser, < wehe@snafu.de >
v2.4, 9 February 1999
An introduction to Linux and infrared devices and how to use the soft&SHY;
ware provided by the Linux/IrDA project. This package uses IrDA(TM)
compliant standards. IrDA(TM) is an industrial standard for infrared
wireless communication, and most laptops made after January 1996 are
equipped with an IrDA(TM) compliant infrared transceiver. Infrared
ports let you communicate with printers, modems, fax machines, LANs,
and other laptops. Speed ranges from 2400bps to 4Mbps. The Linux/IrDA
stack supports IrLAP, IrLMP, IrIAS, IrIAP, IrLPT, IrCOMM, IrOBEX, and
IrLAN. Several of the protocols are implemented as both clients and
servers. There is also support for multiple IrLAP connections, via
several IrDA(TM) devices at once. The Linux/IrDA project started at
the end of 1997 and its status is still experimental, so please don't
expect every feature working straight. AFAIK Linux/IrDA is the _only_
open source IrDA implementation currently available. Remote Control
(RC) via infrared is not the aim of the project, though partly treated
in this HOWTO.
______________________________________________________________________
Table of Contents
1. Introduction
2. Prerequisites
3. Kernel
3.1 General Parameters
3.2 IrDA Specific Parameters
3.2.1 IrDA subsystem support
3.2.1.1 IrDA protocols
3.2.1.2 IrDA protocol options
3.2.1.3 IrDA compressors
3.2.2 Infrared-port device drivers
3.2.2.1 IrTTY (uses serial driver)
3.2.2.2 Dongle support
3.2.2.3 FIR support
4. Linux/IrDA-Utils
5. Configuration
5.1 General Configuration
5.2 IrManager
5.3 Low Level Drivers
5.3.1 SIR
5.3.2 Dongle Connection - Infrared Adapters for the Serial Port
5.3.3 Dongle Connection - Infrared Motherboard Adapter
5.3.4 Fast InfraRed (FIR)
6. Specific Connections and Protocols
6.1 Printer Connection - IrLPT
6.2 LAN Connection - IrLAN
6.3 Palm III Connection - IrOBEX
6.4 Cellular Phone Connection
6.5 Digital Camera Connection
6.6 Window$95 and Linux/IrDA
6.7 Linux to Linux Connection
6.7.1 Connection Methods
6.7.2 Compression
6.8 Multiple Instances
7. Hardware Supported by Linux/IrDA
7.1 Obtaining Information about the Infrared Port in Laptops
7.1.1 SIR
7.1.2 FIR
7.2 Hardware Overviews
8. GUI
9. Power Saving
10. Troubleshooting, Mailing List
10.1 General Information
10.2 Troubleshooting Techniques
11. Known Bugs
12. FAQ
13. Infrared Remote Control
13.1 Resources
13.2 Infrared Remote Control - IrDA
14. Infrared and Eye Safety
15. Credits
16. Revision History
17. Copyright and Disclaimer
______________________________________________________________________
1. Introduction
Better red, than dead. - Unknown AuthorEss
Since 2.1.131 and 2.2.0 Linux/IrDA is part of the kernel. Please note
that the status of the project is still experimental. If you need
information about Linux/IrDA support for 2.0.x kernels please look
into the former version of this HOWTO at
http://www.snafu.de/~wehe/index_li.html. But AFAIK this package is no
longer maintained.
Companies and developers which are interested in joining these efforts
should contact the Linux/IrDA project at
http://www.cs.uit.no/~dagb/irda or me at < wehe@snafu.de >.
Some history about Linux/IrDA. The project started at the end of 1997
with the name Linux/IrDA. Due to some troubles with the name IrDA,
which is trademarked by the Infrared Data Association IrDA
http://www.irda.org/, the name was changed to Linux/IR. At the end of
1998 the the relationship between both became better and the name was
changed to Linux/IrDA again.
This document is based on the "How to use" part of the Linux/IrDA
project homepage http://www.cs.uit.no/~dagb/irda/howto.html. I also
included material provided by the Linux/IrDA core team, the Linux/IrDA
mailing list and other sources.
The document is included in the LINUX DOCUMENTATION PROJECT
http://metalab.unc.edu/LDP.
The latest version of this document is available at
http://www.snafu.de/~wehe/index_li.html
I tried to check all information but I don't have all the necessary
infrared hardware yet, so if something doesn't work for you, please
don't blame me.
Please feel free to contact me for comments or questions. I know this
material is not finished or perfect, but I hope you find it useful
anyway.
<Werner Heuser>
2. Prerequisites
· BIOS
- Make sure your infrared port is enabled in the BIOS and check
what interrupt and port address it uses.
· Infrared Controller Chip
- Make sure your infrared port is detected by the Linux kernel. For
detailed information see the "Hardware Overview" section below.
· modutils
- Make sure you use modutils 2.1.x by insmod --version. I use
version 2.1.121.
· Shared Library
- The shared library libc.so.5 and the loader ld-linux.so.1 has to
be available.
- But glibc2 aka libc6 should work also.
- I am not sure wether you need the zlib library if you use the
data compression features.
· GUI
Currently there are two GraphicalUserInterface's for Linux/IrDA
under development:
· GNOBEX A GNOME application developed by Dag Brattli
http://www.cs.uit.no/~dagb/irda/irda.html with support for drag'n
drop from the GNOME file manager (gmc). It will also show the
progress of the file transfer and give some better error messages
when something goes wrong. The GUI isn't finished yet, but if you
want to try the GUI you will need the Perl-GTK+ module.
· KDE A KDE application developed by Thomas Davis. Look at his page
http://www.jps.net/tadavis/irda.
For all you lurkers out - here's your chance to contribute! Both
GUI's need some icons. Any icons need to be: a) set size (48x48
pixels seems to be a common size, I think) b) large & mini (ask
about size for that; mini's are for docking and such) c) 16 colors
d) free for use. e) please, don't blatently copy MS icons! Please
contact the developers.
· Security
- Most important, you must sync your disks!!! Maybe you have to
reboot your machine. Have you read the disclaimer?
· Miscellaneous
- Other useful progs: APSFILTER, EZ-Magic, MagicFilter or something
similar for the printer configuration.
3. Kernel
Please read the Kernel-HOWTO to get more information about the
compilation process. You'll find the Linux/IrDA code in:
/usr/src/linux/net/irda (protocol stuff)
/usr/src/linux/drivers/net/irda (device drivers)
/usr/src/linux/include/net/irda (header files)
3.1. General Parameters
- Make sure you use kernel 2.2.x sources. If unsure about your kernel
version try uname -r.
- Get the latest kernel patch from the Linux/IrDA project
http://www.cs.uit.no/~dagb/irda/snapshots/. Put it into /usr/src or
where else your kernel sources live and apply something like (replace
patch-2_2.0-irdaXXX with the actual file name):
______________________________________________________________________
cd /usr/src
tar xvzf patch-2_2.0-irdaXXX.tar.gz
cd linux
patch -p1 -l < ./patch-2_2.0-irdaXXX
______________________________________________________________________
- Experimental support has to be enabled (CONFIG_EXPERIMENTAL).
- Enable sysctl in "General Setup" (CONFIG_SYSCTL).
- You should have proc file system support (CONFIG_PROC_FS).
- Also serial support for the SIR features (CONFIG_SERIAL).
- I am not sure wether there has to be printer support for using a
printer with Linux/IrDA (CONFIG_PRINTER). But I assume this feature is
not necessary.
- Networking support must be enabled (CONFIG_NET).
- Make sure you have module support (CONFIG_MODULES) in your kernel!
Test it e.g. with lsmod.
- Also kerneld support is recommended (CONFIG_KERNELD). But kmod
(CONFIG_KMOD) also works. A monolithic kernel seems to work, too.
- Matt Francis wrote: "I notice that some of the modules appear to
want not only module support (as noted on the webpage), but also misc
user device support." (CONFIG_UMISC).
If you only apply the Linux/IrDA patch, you should not have to do a
make clean, so that should save you some time. I suggest you do
something like this:
______________________________________________________________________
make dep && make all && make modules && make install && make modules_install
______________________________________________________________________
If you get really strange errors, then try to rebuild from scratch
after a make clean.
3.2. IrDA Specific Parameters
The following is my suggestion for
../linux-2.2.x/Documentation/Configure.help, parts are from Dag
Brattli and Andreas Butz:
3.2.1. IrDA subsystem support
CONFIG_IRDA
IrDA(TM) is an industrial standard for infrared wireless
communication. Infrared ports let you communicate with printers,
modems, fax machines, LANs, and laptops. Speed ranges from 2400bps to
4Mbps. To use this features you need the irda_utils provided by the
Linux/IrDA project http://www.cs.uit.no/ dagb/irda/ Further
information you may find there and in the Linux/IR-HOWTO at
http://www.snafu.de/ wehe/index_li.html Currently it is recommended to
build IrDA support as modules only. Please see
Documentation/modules.txt. Please note the status of Linux/IrDA is
still experimental.
3.2.1.1. IrDA protocols
· IrLAN protocol
CONFIG_IRLAN
Builds the IrDA network device. Use ``ifconfig eth0 <IP-NUMBER>''
to configure it. - Just say Y
· IrLAN client support
CONFIG_IRLAN_CLIENT
If you connect to infrared devices via IrLAN one has to be the
server and the other the client. You can use both the client and
the server at the same time. The first one to connect becomes the
client. - Just say Y Note: The latest patch includes peer-to-peer
support instead.
· IrLAN server support
CONFIG_IRLAN_SERVER
If you connect to infrared devices via IrLAN one has to be the
server and the other the client. You can use both the client and
the server at the same time. The first one to connect becomes the
client. - Just say Y Note: The latest patch includes peer-to-peer
support instead.
· IrOBEX protocol
CONFIG_IROBEX
IrOBEX is a protocol for exchanging objects (files, vcards, etc.)
over an infrared connection. You can use it to exchange files
between linux and a PALM III. IrOBEX can also be used between two
Linux boxes, Linux and Windows95, etc. - Just say Y
· IrCOMM protocol
CONFIG_IRCOMM
Over IrCOMM you may communicate with cellular phones, etc. To use
this service you have to build a new device with ``mknod
/dev/irnine c 60 64'', which works like /dev/ttySx. - Just say Y
..Note: major and minor number are still not the official ones yet.
For latest improvements (IrSocket is on the way!), please look at
the page of Takahide Higuchi
http://www.pluto.dti.ne.jp/ thiguchi/irda/
..Note: At the moment IrCOMM seems to crash your kernel easily, you
should probably wait for the next patch.
· IrLPT client support
CONFIG_IRLPT_CLIENT
Say Y here if you want to build support for the IrLPT client
protocol. If you want to compile it as a module, say M here and
read Documentation/modules.txt. The IrLPT client protocol can be
used to print documents to IrDA compatible printers like the
HP-5MP, or IrLPT printer adapters like the ACTiSYS IR-100M. - Just
say Y
· IrLPT server support
CONFIG_IRLPT_SERVER
Say Y here if you want to build support for the IrLPT server
protocol. If you want to compile it as a module, say M here and
read Documentation/modules.txt. The IrLPT server protocol makes it
possible to use a Linux machine as an infrared printer server for
other laptops. So if your Linux machine has a cable connection to a
printer, then other laptops can use the Linux machine to print out
documents using infrared communication. - Just say Y
3.2.1.2. IrDA protocol options
CONFIG_IRDA_OPTIONS
You may define some IrDA protocol options.
· Cache last
LSAP CONFIG_IRDA_CACHE_LAST_LSAP
Say Y here if you want IrLMP to cache the last LSAP used. This
makes sense since most frames will be sent/received on the same
connection. Enabling this option will save a hash-lookup per frame.
If unsure, say Y.
· FAST RRs
CONFIG_IRDA_FAST_RR
Use this option if you want to send faster RR (Receive Ready)
frames if the transmit queue is empty. This will give you much
better latencies but will consume more power, because of the
bouncing RR frame.
· Recycle RRs
CONFIG_IRDA_RECYCLE_RR
In the normal life of the IrLAP protocol, it sends a lot of small
RR (Receive Ready) frames over the link (at least when it has
nothing else to do). Saying Y to this option will make IrLAP
recycle these frames thus avoiding many alloc_skb's and
kfree_skb's. To do this it will only buffer one of these frame
which is enough for the usual case.
· Debug information
CONFIG_IRDA_DEBUG
Say Y here if you want the IrDA subsystem to write debug
information to your syslog. You can change the debug level in
/proc/sys/net/irda/debug. If unsure, say Y (since it makes it
easier to find the bugs).
3.2.1.3. IrDA compressors
CONFIG_IRDA_COMPRESSION
You may use the compression methods BZIP2 and BSD. These are not IrDA
standard. This will allow two linux boxes to handshake compression. It
should be compatible with other IrDA devices, although communication
will not be compressed then.
· Deflate compression (experimental)
CONFIG_IRDA_DEFLATE
Say Y here if you want to build support for the Deflate compression
protocol. If you want to compile it as a module, say M here and
read Documentation/modules.txt. The deflate compression (GZIP) is
exactly the same as used by the PPP protocol. Enabling this option
will build a module called irda_deflate.o.
· BZIP2 compression
CONFIG_IRDA_BZIP2
Help not available yet.
· BSD compression
CONFIG_IRDA_BSD
Help not available yet.
3.2.2. Infrared-port device drivers
Three sorts of low level infrared drivers are available: serial,
dongle and FIR. They will show up in /proc/net/dev (irda0) after
initialisation.
3.2.2.1. IrTTY (uses serial driver)
Most IrDA chips support StandardInfraRed (SIR), which works up to
115200bps and emulates a serial port (16550A UART). On many laptops
this port is detected by the serial support of the kernel, see
``dmesg''. IrTTY connects the Linux/IrDA services to this port. - You
should say Y here.
· Serial dongle support
CONFIG_IRTTY_SIR
Say Y here if you want to build support for the IrTTY line
discipline. If you want to compile it as a module, say M here and
read Documentation/modules.txt. IrTTY makes it possible to use
Linux's own serial driver for all IrDA ports that are 16550
compatible. Most IrDA chips are 16550 compatible so you should
probably say Y to this option. Using IrTTY will however limit the
speed of the connection to 115200 bps (IrDA SIR mode). If unsure,
say Y.
3.2.2.2. Dongle support
CONFIG_DONGLE
Currently four dongles (infrared adapters for the serial port) are
supported. The dongle is an infrared device which may be connected to
serial port, if you don't have built-in infrared support for your
machine. If you use a dongle together with a laptop you maybe have to
disable the IrDA support in the BIOS.
· ESI JetEye PC dongle
CONFIG_ESI_DONGLE
Say Y here if you want to build support for the Extended Systems
JetEye PC dongle. If you want to compile it as a module, say M here
and read Documentation/modules.txt. The ESI dongle attaches to the
normal 9-pin serial port connector, and can currently only be used
by IrTTY. To activate support for ESI dongles you will have to
insert ``irattach -d esi'' in the /etc/irda/drivers script.
http://www.extendsys.com/support/ftp/infrared.html
· ACTiSYS IR-220L and IR220L+ dongle
CONFIG_ACTISYS_DONGLE
Say Y here if you want to build support for the ACTiSYS IR-220L and
IR220L+ dongles. If you want to compile it as a module, say M here
and read Documentation/modules.txt. The ACTiSYS dongles attaches to
the normal 9-pin serial port connector, and can currently only be
used by IrTTY. To activate support for ACTiSYS dongles you will
have to insert ``irattach -d actisys'' or ``irattach -d
actisys_plus'' in the/etc/irda/drivers script.
http://www.actisys.com
· Tekram IrMate 210B dongle
CONFIG_TEKRAM_DONGLE
Say Y here if you want to build support for the Tekram IrMate 210B
dongle. If you want to compile it as a module, say M here and read
Documentation/modules.txt. The Tekram dongle attaches to the normal
9-pin serial port connector, and can currently only be used by
IrTTY. To activate support for Tekram dongles you will have to
insert ``irattach -d tekram'' in the /etc/irda/drivers script.
http://www.tekram.de/
·
CONFIG_GIRBIL_DONGLE
Say Y here if you want to build support for the Greenwich
Instruments GirBIL dongle. If you want to compile it as a module,
say M here and read Documentation/modules.txt. The Greenwich dongle
attaches to the normal 9-pin serial port connector, and can
currently only be used by IrTTY. To activate support for Greenwich
dongles you will have to insert ``irattach -d girbil'' in the
/etc/irda/drivers script. http://www.greenwichinst.com/
3.2.2.3. FIR support
FastInfraredSupport (FIR) needs a specific controller chip, which
supports up to 4Mps. - Just say Y
· NSC PC87108
CONFIG_NSC_FIR
NationalSemiConductor NSC PC87108 FIR chip e.g. used in the IBM
Thinkpad 560X and ACTiSYS IR2000 dongle. Probably the NSC PC87338
FIR chip is also supported. The driver supports SIR, MIR and FIR
(4Mbps) speeds. - Just say Y
· Winbond W83977AF (IR)
CONFIG_WINBOND_FIR
Winbond W83977AF (IR) FIR chip e.g. used in the Corel Netwinder PC.
The driver supports SIR, MIR and FIR (4Mbps) speeds. - Just say Y
· Sharp UIRCC
CONFIG_SHARP_FIR
Say Y here if you want to build support for the Sharp UIRCC IrDA
chipset. If you want to compile it as a module, say M here and read
Documentation/modules.txt. This chipset is used by the Toshiba
Tecra laptops.
4. Linux/IrDA-Utils
· Use the latest source snapshot of irda-utils available at
http://www.cs.uit.no/~dagb/irda/irda-utils/
· Untar the package with tar xvzf irda-utils<VERSION>. I recommend to
do this in /usr/src.
· Do a make depend.
· Do a make clean (not necessary if you compile the package for the
first time).
· Do a make all to build the binaries.
· Do a make install, this brings irattach and irmanager into the
right place and installs some config files in /etc/irda.
A recommendation from Bjoern Hansson <Bjorn.Hansson@signal.uu.se>: If
make depend fails on stdef.h and stdarg.h just add -I/usr/lib/gcc-
lib/i586-linux/egcs-2.90.29/include/ or the according path for your
system to the SYS_INCLUDES line in Makefile.
5. Configuration
5.1. General Configuration
· First you should put your IR devices in range. Though it might be
possible that the Linux/IrDA service detects every new device
automagically I only have good experience with the devices in range
during the configuration process.
· Keep your infrared devices together in a range below one meter and
an angle of 30 degree. There has to be a direct line of sight
between them. If this is not possible, you may use a mirror (an
unused M$ CD should work quite good).
· Add the following lines to your /etc/conf.modules file:
___________________________________________________________________
alias tty-ldisc-11 irtty #
alias char-major-60 ircomm_tty # if you want IrCOMM support
___________________________________________________________________
I'm really not sure about those parameters anymore. There is conflict&SHY;
ing information on Dag Brattli's pages and on the list. Though they
had to be used with former versions of the Linux/IrDA package, this
behaviour probably changed with the version for 2.2.x kernels.
· Have a look into the files in /etc/irda. They are similar to the
files in /etc/pcmcia. Edit /etc/irda/drivers to reflect your setup.
Most people will use irattach from that file. The files are:
___________________________________________________________________
Makefile
network*
network.redhat*
serial
drivers
network.opts
obex
printer
___________________________________________________________________
· Run depmod -a.
5.2. IrManager
Dag Brattli wrote: " IrManager [...].is a user-space daemon that is
inspired and quite similar to the cardmgr used in the PCMCIA
distribution.
The IrManager will receive events from the kernel level side of the
protocol stack. When the IrManager receives an event it can execute
shell commands and scripts, so I have added the /etc/irda directory
which will contain such scripts. [...]
For example, if IrLMP discovers a remote device with IrLAN provider
capabilities and no local IrLAN client has registered, then IrLMP will
send an event to the IrManager and make it "modprobe" the module
required. [...]
When application level clients are ready for communication and user-
space configuration, they can also notify IrManager about this, so
that it can execute the right script. For example IrLAN will send the
event EVENT_IRLAN_START when the data channel is ready for exchanging
Ethernet frames. When IrManager receives this event, it will execute
/etc/irda/network start <devname> to configure the network interface.
This network script is actually the same as used by the PCMCIA code
and since I'm using the Redhat variant of it, it will in turn execute
/sbin/ifup <devname>.
So by using the IrManager, I "only" have to do this when I start the
stack:
______________________________________________________________________
irattach /dev/ttyS2 &
irmanager -d 1 # -d 1 means: start discovery process
______________________________________________________________________
and then when my laptop discovers the IrLAN provider (HP Netbeamer in
my case) it will ask IrManager to load the module irlan_client. When
the connection is up and ready, it will ask it to execute
/etc/irda/network start eth0. When the connection is broken, it will
again ask it to take down the interface using /etc/irda/network stop
eth0.[...]
That's all to get it working if you are using Redhat. If you are using
some other distribution which doesn't have /sbin/ifup, then you better
copy /etc/pcmcia/network.opts to /etc/irda/network.opts or configure
the file yourself.
If you want to use the IrLAN server, you will still have to modprobe
irlan_server before you start the irmanager _without_ -d 1.
And just like the cardmgr, you will (if you want to) get the beeps
when the connection is up and running and when it is disconnected!!!
I hope that we can add such scripts for all the other clients/services
that need user level configuration. It would be really cool to have a
/etc/irda/printer script for configuring IrDA(TM) capable printers. So
if you get in range of an IrDA(TM) capable printer, then IrManager
should load the irlpt_client module, and also configure the other
stuff that needs to be done for using this printer.
I also hope that we can use the config file for configuring IrDA(TM)
ports and device drivers. Something like:
______________________________________________________________________
Device Drivers
module "irtty" script="irattach /dev/ttyS2"
module "smc_ircc" irq=11 port=0x34f
______________________________________________________________________
So that IrManager can load and start all these when it is executed. In
this way we would only have to start IrManager in
/etc/rc.d/init.d/irda and the rest would be plug and play. There would
be no need for manually starting programs and configuring devices.
When irmanager receives the following events for a device <dev> it
will currently do:
EVENT_IRLAN_START, start and configure the device using /sbin/ifup
<dev>
EVENT_IRLAN_STOP, close the device using /sbin/ifdown <dev>
This can however be easily changed by the user, if this is not what is
the prefered behaviour.
5.3. Low Level Drivers
There are three sorts of low level drivers: SIR, dongle and FIR. If
the right driver is detected by the kernel you get a message like:
______________________________________________________________________
IrDA irda_device irda0 registered.
______________________________________________________________________
5.3.1. SIR
· Try to find out which serial port is used by the IR device. You may
do so by watching the output of dmesg. If serial support is
modularized do an insmod serial first. Look for an entry like:
___________________________________________________________________
Serial driver version 4.25 with no serial options enabled
ttyS00 at 0x03f8 (irq = 4) is a 16550A #first serial port /dev/ttyS0
ttyS01 at 0x3000 (irq = 10) is a 16550A #e.g. infrared port
ttyS02 at 0x0300 (irq = 3) is a 16550A #e.g. PCMCIA modem port
___________________________________________________________________
If this is not the case, you either don't have infrared support
enabled in the BIOS or your infrared device is not detected by the
kernel. Currently I know only two laptop models with this effect, the
HP OmniBook 800 and the Toshiba Libretto models. I am not sure whether
PnP support effects the detection of the IR port. If you are unsure
try it out and let me know the results.
· In some situations you may have to use setserial /dev/ttyS<0-2>
port 0xNNNN irq M to set the values for your infrared serial port,
especially if the infrared port is a separate serial line. You
usually don't need to change the values! For further information
look into the FAQ section below.
· If you don't use kerneld or kmod insert the irda module with
modprobe irda.
· Do lsmod. It should show the modules irda and irtty now.
· A look into /var/log/messages should show the entry "Serial
connection established" now.
· Say irmanager -d1, which will start the necessary programs, such as
irattach.
· Give irattach some time, e.g. seven seconds, to detect other IR
devices. Then watch the output from the kernel that you will
hopefully get in /var/log/messages. It should look like the
following (I removed some lines, which were not related to
Linux/IrDA):
Jan 2 12:57:26 japh kernel: ttyS00 at 0x03f8 (irq = 4) is a 16550A
Jan 2 12:57:26 japh kernel: ttyS02 at 0x03e8 (irq = 4) is a 16550A
Jan 2 12:57:26 japh kernel: Linux Support for the IrDA (tm) protocols (Dag Brattli)
Jan 2 12:59:09 japh syslog: executing: 'echo 1 > /proc/sys/net/irda/discovery'
Jan 2 12:59:09 japh syslog: Setting discovery to 1 exited with status 1
Jan 2 12:59:09 japh syslog: + 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli
Jan 2 12:59:09 japh syslog: + 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli
Jan 2 12:59:09 japh syslog: Serial connection established.
Jan 2 12:59:09 japh kernel: IrDA irda_device irda0 registered.
Jan 2 13:01:22 japh syslog: executing: './drivers start '
Jan 2 13:01:22 japh syslog: Serial connection established.
Jan 2 13:01:42 japh syslogd: Printing partial message
Jan 2 13:01:42 japh 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli
Jan 2 13:02:49 japh kernel: IrDA Discovered: japh
Jan 2 13:02:49 japh kernel: Services: Computer
5.3.2. Dongle Connection - Infrared Adapters for the Serial Port
The currently supported dongles are the Extended Systems Inc. ESI-9680
JetEye, the Tekram IRmate 210B, the ACTiSYS IR220L and 220L+, the
Greenwich GIrBIL. dongle.
Dag Brattli wrote (modified by wh): "To use dongles you have to do
something like this:
______________________________________________________________________
modprobe tekram # or esi or actisys
irmanager -d 1 #
irattach -d tekram # or -d esi or -d actisys
______________________________________________________________________
As you can see, you must still use the -d option with irattach since
it is possible to have two serial ports using different dongles at the
same time (so the tty you are binding must know which dongle it is
supposed to use). So if you have two dongles and two serial ports, you
could do something like this:
______________________________________________________________________
modprobe tekram
modprobe esi
irattach /dev/ttyS0 -d esi &
irattach /dev/ttyS1 -d tekram &
______________________________________________________________________
PS: I would not try to turn the two dongles against each other, since
I really don't know how the stack would react :-) ... Since I don't
have any of these new ACTiSYS 220L+ dongles, I'm not able to test it.
Since the new dongle has support for one extra speed (38400bps), you
must specify the dongles differently with irattach so that the kernel
knows which dongle you are using (and what QoS can be used):
______________________________________________________________________
irattach /dev/ttyS0 -d actisys # for the 220L dongle
irattach /dev/ttyS0 -d actisys+ # for the 220L+ dongle
______________________________________________________________________
The current implementation of dongle support does not have any state
associated with it, so its not possible to use both ACTiSYS dongles
(220L and 220L+) at the same time (connected to two serial ports) for
now. If someone needs to be able to do so, please mail me (Dag
Brattli) and I will think about it!"
Note: When I tried to use an infrared modem (Swissmod 56Ki,
manufactured by Telelink AG) connected to my laptop (IrDA works with
Window$95 only, due to non standard hardware) I had to remove the
infrared support in the BIOS to get it working!
5.3.3. Dongle Connection - Infrared Motherboard Adapter
Support for the ACTiSYS IR2000 dongle has been implemented in a file
called pc87108 which you can either compile into the kernel or
insmod/modprobe to insert the module:
______________________________________________________________________
irmanager -d 1
modprobe pc87108
______________________________________________________________________
or insert modprobe pc87108 into the /etc/irda/drivers file (I think).
5.3.4. Fast InfraRed (FIR)
The IrDA(TM) standard knows three kinds of speeds:
1. SIR = Standard IrDA, up to 115kbps IrDA,
2. MIR = Medium Speed IrDA,
3. FIR = Fast IrDA (4Mbps),
4. VFIR = Very Fast IrDA(16Mbps), seems to become a future standard
Up to 115.200bps many infrared controllers work like a serial port.
Up to 4Mbps they work in "FIR mode". Currently there are two chips
supported: NationalSemiConductor NSC PC87108 e.g. used in IBM
Thinkpad 560X and Winbond W83977AF (IR) FIR chip e.g. used in the
Corel Netwinder PC. You may start the FIR service by loading the
according module. Linux/IrDA will probe your hardware then.
6. Specific Connections and Protocols
6.1. Printer Connection - IrLPT
IrLPT is under heavy construction at the moment. The client side
should work, but the server side may crash.
· Remove any current print jobs with lprm "*".
· If you don't use kerneld do a modprobe irtty.
· Do a modprobe irlpt_client.
· Check the modules with lsmod. This should show: irda, irtty and
irlpt_client
· cat /proc/misc. Gives you the minor device-number . It is the first
number in the line with irlpt0.
· su to root, and do mknod /dev/irlpt0 c 10 <minor device-number>.
Note: Something like ./MAKEDEV irlpt0 is not possible yet. But
maybe load_misc irlpt works, though I couldn't test this yet.
· Try to write a small file to /dev/irlpt0 by cat FILE >/dev/irlpt0
(do not wonder about a bad format this is just a first check). For
me this didn't always work, but I couldn't find out why not.
· The better way is to change your /etc/printcap to use /dev/irlpt0
in addition or instead of /dev/lp1. See Printing-HOWTO for detailed
information.
· For easy printer setup you may use a printing software like
APSFILTER, MagicFilter EZ-Magic (with RedHat there should also be a
GUI for this purpose). Make a copy of /etc/printcap before.
· Example for APSFILTER with a HP 6P (non-postscript, HP 6MP is with
postscript). The two relevant questions are:
"Do you have a (s)serial or a (p)arallel printer interface?"
Answer "p"
"What's the device name for your parallel printer interface?"
Answer "/dev/irlpt0"
· Restart the print daemon with kill -HUP <PID of lpd>. If you use
another print daemon choose the according command.
· Watch whether the connection indicator of your printer shows
activity, e.g. the green light above the IR port of a HP 6P/MP
comes on (lower left hand corner, near the paper tray).
· I couldn't get to manage printjobs larger than approximately 10
pages yet. But maybe this depends on the memory size of my
hardware, which is 16MB. There seems to be a problem with the
software too, Thomas Davis wrote: "I will ... limit the irlpt, so
it won't eat memory when you send a large print file.".
Takahide Higuchi reported: " I have been debugging IrCOMM with a
printer ( Canon BJC-80v ) with IrDA port and IrCOMM protocol (not
IrLPT). I can print a short e-mail text though, it easily causes dead
lock when I try to print a postscript with gs."
From the page of Thomas Davis http://www.jps.net/tadavis/irda : To use
the IrLPT server, you need to perform the following steps:
______________________________________________________________________
/sbin/insmod irlpt_server
/sbin/mknod /dev/irlptd c 10 `grep irlptd /proc/misc|cut -f 1`
______________________________________________________________________
At this point, the IrLPT server is ready to recieve print jobs; now;
all you need is this simple shell script
______________________________________________________________________
#/bin/sh
#
while (true)
do
cat /dev/irlptd | lpr
done
______________________________________________________________________
6.2. LAN Connection - IrLAN
· You might connect your Linux box using IrLAN to another network
device such as a Linux box with IrLAn, a HP NetBeamer or a
Window$95 box with Inrared Network Device support.
· Dag Brattli wrote: "If you want to use IrLAN you must modprobe
irlan_client before ifup eth0. I had to remove the request_module()
stuff since that needed a process context which I don't have in the
kernel. "
· Run ifconfig eth0 up <ip_address> netmask <ip_netmask> to configure
it with IP-address and other parameters. If the protocol is still
running you may start communicating. It is possible to use RedHat's
netcfg to do this, since it makes it very easy. Next time you only
need to do /sbin/ifup eth0.
· Test the network device by pinging to it. For detailed information
about further setup see the NET3-HOWTO.
· Do not forget to add a route, e.g. route add default gw
<ip_gateway> or route add -host <target host> dev eth0.
· Ping to another IP now, to test the connection.
· For testing reasons I recommend only to use one laptop and one IR
ethernet device in the same room. If there are problems look which
different modes for the IR ethernet device are possible. Try them.
For an ACTiSYS FIR board and dongle you may do:
______________________________________________________________________
irmanager -d1
/sbin/modprobe pc87108 # remove irattach from /etc/irda/drivers, or
# substitute irattach with the modprobe!
______________________________________________________________________
On machine 1:
______________________________________________________________________
modprobe irlan_client # not really necessary since irmanager should do this!
______________________________________________________________________
On machine 2 (if you don't have an access-point)
______________________________________________________________________
modprobe irlan_server
______________________________________________________________________
Do not compile irlan_server into the kernel, since it currently does
not like that! You should have configured /etc/sysconfig/network-
scripts/ircfg-eth0 with a proper ad-hoc network if you are using two
machines. If you have an access-point, then the normal setup should be
fine.
Notice that in the latest patch (2.2.0-irda1) irlan_client will call
the device irlan0 by default, but you can change this by giving eth=1
as an option to irlan_client (modprobe irlan_client eth=1 or options
irlan_client eth=1 in /etc/conf.modules). The next release of IrLAN
will be only one module, so you don't need to think about if you need
to have the client and/or the server installed.
It's possible to do ifconfig irlan0 -broadcast to stop the AP from
flooding you with broadcast frames! That can be a problem if you are
connected to a very large Ethernet segment. The only problem is that
your machine will then have to initiate all communications and can
therefore not function as a server (well, you could probably make a
stationary machine somewhere answer ARP requestes on your behalf).
6.3. Palm III Connection - IrOBEX
The IrOBEX stuff seems under rapidly improving changing development.
So the applications change too. Therefore I just can't give quite
exact information. Please see also the report by Dag Brattli at
http://www.cdpubs.com/hhsys/archives/66/10brattl.pdf .
The /etc/irda script is really only good for configuration of the
devices, making the right mknod for /dev/irobex etc, not for starting
applications.
· Palm III -> Linux
1) Terminal 1> irattach /dev/ttyS<x>
2) Terminal 2> load_misc irobex
3) Terminal 3> Start irobex_app in the irobex directory. I suppose
irobex_app is not working anymore. Now you should use the
gtk/irobex program instead! You need to have the gtk library
installed to use this program. A command line frontend should be
programmed by someone. Maybe the programm to use is irobex_receive.
4) Beam something from your Palm III.
5) If everything is successful, you can take a look at a new file
that has been created in the directory in which you started
irobex_app (or in /tmp for irobex_receive). This file will be named
after the object you just transfered.
· Linux -> Palm III
This should also be possible, but I don't have any further
information right now.
· PPP
Rui Oliveira wrote: "This is just to let you know that with the
latest IrCOMM patch (050998) of Takahide Higuchi, I managed to
HotSync and establish a PPP connection between my Palm III and my
Linux box. I'm using IRLink (from IsComplete) to redirect the
serial port to ir. Communication with pilot-xfer works flawlessly.
Although I was able to establish a PPP connection, I'm still unable
to fetch mail and do Web browsing. This is probably due to
connection time-outs. I am checking this out.". Please see the PPP-
HOWTO for further information about PPP.
· IrCOMM
Jon Howell wrote: "I thought I'd try IrCOMM, since the Palm III can
be made to reroute serial info to the IR port (using IrLink from
IS/Complete, available at www.palmcentral.com), and then you can
run a terminal program (like "PalmTelnet" in serial mode) over
IrDA. I can only assume it's using the IrCOMM protocol. I've tested
this configuration between two palm pilots, but of course I can't
know what the protocol running over the IR is.
I couldn't figure out what to do with the IrCOMM code. I see from
the status page that there's "Client support (should start to get
usable), " but I can't find any docs that indicate how it has to be
used. "
6.4. Cellular Phone Connection
As far as I know some cellular phones use the IrCOMM standard, e.g.
Ericsson SH888 and NOKIA 8110. Benny Amorsen wrote: "I have used
minicom with the SH888, and I actually got it to establish a
connection in minicom (CONNECT 9600...). I could not get it to do
anything after that, and hanging up by dropping carrier does not work.
+++ worked, so I could hang up that way. I would say that the SH888 is
very close to working with linux-irda., and actually it might work in
2.0.x kernels. I only use 2.1 kernels.".
Maybe other cellular phones use the IrOBEX standard, see the Palm III
section for information about setting up a connection.
Carlos Vidal wrote: Correct me if I'm wrong, but it seems to me that
Nokia telephones do not contain a genuine hardware modem, but
something which is similar in principle to WinModems for PC. Whenever
Nokia writes about modem communication, they use the name "Windows
software modem" (or something similar). Which is actually backed up by
the need to use special Nokia software for Windows (called Nokia
Cellular Data Suite).
Joonas Lehtinen wrote: This is true with 61xx models. Models: 8810,
9000(i) and 9110 should work fine. (They have inbuilt modem). My N9000
reports IrCOMM with linux.
To start a communication session with /dev/irnine, for instance, say:
______________________________________________________________________
dip -t
> port irnine
> term
______________________________________________________________________
Probably you may use cu instead of dip, too. There are also reports
about some efforts with the Ericsson GF768 and IR Modem DI 27.
Benny Amorsen wrote: The SH888 emulates an IRDA-port when you connect
it using the serial cable. Why someone would think up something weird
like that is beyond me, but that is the way you get it to work in
Windows. Not that I ever managed to make it work in Windows, though.
6.5. Digital Camera Connection
Markus Schill wrote: "Great that there are also other people who are
interested in using the SONY DSC-F1 IR adapter under linux. Up to now
I have only toyed around with the linux-irda software and the serial
IR adapter from PuMa Technologies that came with the camera. This is
the status. I am using linux 2.0.33 and the latest linux-irda... If I
use:
______________________________________________________________________
insmod irda
insmod irtty
irattach /dev/cua0
______________________________________________________________________
the adapter starts talking to the camera. /var/log/messages says that
SONY-DSC-F1 was found, but no service is started. (Please note, this
probably doesn't apply to the 2.2.x kernel versions of Linux/IrDA,
wh).
There are two programs for linux available that can be used for the
communication with the camera via cable: (1) chotplay and (2)
stillgrab. They both take a tty as commandline option, so I guess that
they should work if the irtty layer of the protocol stack works
correctly ... I have not looked at anything in the linux-irda code,
yet!). I am not sure whether I understand the stack but shouldn't the
irtty make the thing look like a normal tty? What service should be
started. "
Dag Brattli wrote: "I'm not sure which application level protocol the
camera uses, but it is possible that it implements the IrDA(TM)
Infrared Transfer Picture Specification (IrTran-P). If you take a look
at http://www.irda.org/standards/pubs/IrTran-P_10.pdf, you will see
that it is a protocol which is implemented above IrCOMM (not IrTTY!).
IrTTY is something we use just to be able to talk to the Linux serial
driver. "
6.6. Window$95 and Linux/IrDA
Introduction
Why this? Unfortunately Linux users are not always supported with the
necessary hardware information. Sometimes it is possible to look at
this informations in Window$95.
Where to get it from? At
http://www.microsoft.com/windows95/info/irda.htm you will find a
support pack "Infrared Transfer 2.0". It is a self-extracting archive
W95IR.EXE with 331KB.
With some machines e.g. a HP Omnibook 800 it is necessary to use a
vendor specific version of this package (e.g. for the HP Omnibook 800
you may find it on the recovery CD).
Especially the ..\windows\inf\*.inf files and the device manager are
of interest to look for configuration details.
As far as I know Window$NT doesn't support IrDA(TM). About Window$98 I
have heard there is no IrDA(TM) support yet.
There are also some non M$ products available. Note: Some of them use
proprietary infrared protocols:
· CounterPoint: QuickBeam 1.15
· LapLink 7.5
· CarbonCopy 32 4.0
· pc ANYWHERE 7.5
· Puma Technology: TRANXIT pro 4.0
Connection between Linux/IrDA and Window$95 IrDA(TM)
I suppose there are three ways to connect Linux/IrDA and Window$95:
A network connection between two PC's. If you have set up Infrared
Transfer 2.0, you will find an IrDA(TM) network device in the <Network
Device Section>. But I couldn't get a working connection yet.
Maybe it is also possible to use the IrOBEX protocol. But I don't know
which software to use and where to get it. I supposed the necessary
software comes with a Palm III, but this seems not to be true.
Takahide Higuchi <thiguchi@pluto.dti.ne.jp> provided IrCOMM support.
From his page at http://www.pluto.dti.ne.jp/~thiguchi/irda/ I have
taken the following description (I have modified it at little): "With
IrCOMM support you can send or receive short messages between a linux
box and a terminal program on a win95 laptop! Please add this line to
/etc/conf.modules:
______________________________________________________________________
alias char-major-60 ircomm_tty
______________________________________________________________________
Next, make a device file mknod /dev/irnine c 60 64. Now Linux/IrDA
services can be started as usual with irattach /dev/ttyS? &.
/dev/irnine can be used as a serial device. ircomm and ircomm_tty mod&SHY;
ules will be loaded automatically by kerneld/kmod when a program uses
/dev/irnine. NOTE: I think "setserial" utility will not work on
/dev/irnine. Tips:
· To accept login via IrCOMM, use this as a root: First, please
enable IrDA and IrCOMM. Then edit /etc/inittab and add a line like
this:
___________________________________________________________________
T1:23:respawn:/sbin/getty -L -w irnine 38400 vt100
___________________________________________________________________
and do this as a root: init q. And init will start waiting for incom&SHY;
ing IrCOMM connection. You will see your favorite Linux's login prompt
from terminal emulator on Win95!
· If you try pppd, please consider the -crtscts option to disable
flow-control. I implemented some flow-control emulation but it is
not tested.
· Now my patch reports what kind of features is needed by the peer
infrared device. Messages like this will be written in syslog:
Sep 4 10:01:02 monolith kernel: parse_control:instruction(0x12)
Sep 4 10:01:02 monolith kernel: data:03
· I especially want to know what message SH888 (or other infrared
devices except for win95 PC) says. So please mail me your syslog
generated during IrCOMM connection! If you have a copy of the
IrCOMM specification written by IrDA(TM), please see page 34 or 38,
and you will know what these messages mean."
6.7. Linux to Linux Connection
6.7.1. Connection Methods
There should be three ways to get two Linux machines connected via
Linux/IrDA.
· Dag Brattli wrote about the IrOBEX support: "The awakened reader
may wonder what prevents the beaming of files from Linux to Linux?
Well, nothing!! (but I haven't tried that yet). This means that we
now have a "simple" way of beaming files between Linux laptops. I
think that this may be the "killer app" we all have been waiting
for!" Try to "load_misc irobex at both ends, and then try
iroabex_app get on one of the machines and irobex put <file> on the
other.".
· Via Linux/IrDA network connection. I suppose you have to load the
module irlan_client at one machine and irlan_server at the other
one.
· With IrCOMM support, in other words over a serial line, which could
mean minicom, pppd, etc.
6.7.2. Compression
Please note this feature is still quite experimental! Dag Brattli
wrote: "Just wanted you to know I have just added COMPRESSION support
to IrLAP! As you may know, this is _not_ part of the IrDA(TM)
standard, but Linux can now negotiate with its peer and check if it
has the same compression capabilities). So obviously if you are
talking to Win95, Palm III or whatever, you will _not_ get
compression!!! This is something which is exclusive for Linux as far
as I know! The IrDA(TM) standard says that devices should ignore
unknown field in the negotiation header, so we are still "compatible"
with IrDA(TM) (have just borrowed an unused header value).
If you want to try using the compression code (Linux <-> Linux) you
will have to insert the irda_deflate module some time before you
actually make the connection. I do it before irattach.
The compression standard I have added is the deflate format used by
the zlib library which is described by RFCs (Request for Comments)
1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt (zlib
format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
The compression interface is similar to PPP, so you can add as many
different compressors as you want. Currently there is only support for
GZIP, but BSD compression will be added later."
6.8. Multiple Instances
Dag Brattli wrote: "The IrLAP layer has been enhanced to allow more
than one instance (so I can use IrLAN on my built-in ir-port, and
communicate with the Pilot over the IrDA dongle at the same time) ...
So how do you make two Linux/IrDA connections? Well, you just fire up
irattach for each of the IR ports you have like this: "
______________________________________________________________________
irattach /dev/ttyS0 & (my ESI dongle)
irattach /dev/ttyS2 & (my builtin IrDA port)
insmod irlan_client
insmod irobex
______________________________________________________________________
7. Hardware Supported by Linux/IrDA
7.1. Obtaining Information about the Infrared Port in Laptops
To get the IrDA port of your laptop working with Linux/IrDA you may
use StandardInfraRed (SIR) or FastInfraRed (FIR).
7.1.1. SIR
Up to 115.200bps the infrared port emulates a serial port like the
16550A UART. This will be detected by the kernel serial driver at boot
time or when you load the serial module. If infrared support is
enabled in the BIOS, for most laptops you will get a kernel message
like:
______________________________________________________________________
Serial driver version 4.25 with no serial options enabled
ttyS00 at 0x03f8 (irq = 4) is a 16550A #first serial port /dev/ttyS0
ttyS01 at 0x3000 (irq = 10) is a 16550A #e.g. infrared port
ttyS02 at 0x0300 (irq = 3) is a 16550A #e.g. PCMCIA modem port
______________________________________________________________________
7.1.2. FIR
If you want to use up to 4Mbps, your machine has to be equipped with a
certain FIR chip. You need a certain Linux/IrDA driver to support this
chip. Therefore you need exact information about your FIR chip. You
may get this information in one of the following ways:
1. Read the specification of your machine, though it is very rare that
you will find enough information there.
2. Do a cat /proc/pci, though often the PCI information is incomplete.
You may find the latest information about PCI device and vendor
numbers at the page of Craig Hart
http://members.hyperlink.net.au/~chart . From kernel 2.1.82 on, you
may use lspci from the pci-utils package, too. The according files
for 2.2.x kernels are in /proc/bus/pci.
3. If you have installed the Linux/IrDA software load the FIR modules
and watch the output of dmesg, wether FIR is detected or not.
4. Though I didn't use them for this purpose yet the isapnp tools,
could be useful.
5. Another way how to figure it out explained by Thomas Davis: "Dig
through the FTP site (of the vendor, wh), find the FIR drivers, and
they have (for a SMC chip, wh):
___________________________________________________________________
-rw-rw-r-- 1 ratbert ratbert 743 Apr 3 1997 smcirlap.inf
-rw-rw-r-- 1 ratbert ratbert 17021 Mar 24 1997 smcirlap.vxd
-rw-rw-r-- 1 ratbert ratbert 1903 Jul 18 1997 smcser.inf
-rw-rw-r-- 1 ratbert ratbert 31350 Jun 7 1997 smcser.vxd
___________________________________________________________________
If in doubt, always look for the .inf/.vxd drivers for Win95; Win95
doesn't ship with _ANY_ FIR drivers. (they are all third party, mostly
from Counterpoint, who was assimilated by ESI)."
6. Use the DOS tool CTPCI330.EXE provided in ZIP format by the german
computer magazine CT http://www.heise.de . The information
provided by this program is sometimes better than with the Linux
tools.
7. There is also a small DOS utility made by SMC, called "FindChip".
The package also includes a "FirSetup" utility that is supposed to
be able to set all values except the chip address. Look at
http://www.smsc.com/ftppub/chips/appnote/ir_utils.zip
Warning: The package is not intended for the end user, and some of
the utilities could be harmful. The only documentation in the
package is in M$ Word format. Linux users may read this with
catdoc, available at http://www.fe.msk.ru/~vitus/catdoc/ .
8. Use the Device Manager of Window$95/98/NT.
9. You may also use the hardware overviews mentioned below.
7.2. Hardware Overviews
There are some overviews about Linux and infrared capable devices in
the WWW:
· The Linux/IrDA Project - Hardware Survey at
http://www.cs.uit.no/~dagb/irda/hardware.html
· Takahide Higuchi at
http://www.pluto.dti.ne.jp/~thiguchi/ir/product.html.This page is
in japanese.
· I have also set up a hardware overview at
http://www.snafu.de/~wehe/index_li.html. This list also contains
information about infrared capable devices which are not mentioned
here (mice, printers, remote control, transceivers, etc.).
To make this hardware overview list more valuable it is necessary
to collect more information about the infrared devices in different
hardware. You can help by sending me a short e-mail containing the
exact name of the hardware you have and which type of infrared
controller is used.
Please let me also know how well Linux/IrDA worked, at which tty,
port and interrupt it works and the corresponding infrared device
(e.g. printer, cellular phone) you use.
You can also help by contributing detailed technological
information about some infrared devices, which is necessary to
develope an according driver for Linux.
8. GUI
If you want to try out a little GUI, you can try to run ircp.pl. You
will need the Perl-GTK+ module ( http://www.gnome.org) to make it run.
The GUI is far from finished, so don't expect too much :-)
9. Power Saving
In the specifications of my HP OmniBook 800 it is recommended to turn
off the IR port, if it is not in use, because it may consume up to 10
percent of the battery time.
If necessary, you may also try to disable the Fast RRs feature in the
IrDA section of the kernel. This option will give you much better
latencies but will consume more power.
10. Troubleshooting, Mailing List
10.1. General Information
If you encounter problems. Try the following:
· Read the FAQ section below.
· Look at /var/log/messages and/or /var/log/kern.
· Do a dmesg.
· Look at the different files in /proc/irda.
· Look at the mailing list archiv at
http://www.ita.chalmers.se/~svinto/hypermail/irda/, whether your
problem is already known.
· Ask in the Linux/IrDA mailing list. To join the Linux-IrDA mailing
list, send a mail to linux-irda-request@list.uit.no with
"subscribe" in the email body. Use linux-irda@list.uit.no to post a
message. You are welcome to use this mailing list for posting
questions, answers, bug-reports, patches, suggestions and comments.
To avoid spam, the list is now moderated, so there may be some time
before your posting is distributed to the other list members.
10.2. Troubleshooting Techniques
Although I'm not much of a hacker I collected some tricks to track
errors or bugs in the Linux/IrDA software.
· You may set the debug level in /proc/sys/net/irda/debug to 1, 2, 3,
4.
· Use the files in /proc/sys/net/irda to try different parameters
like echo 0 > /proc/sys/net/irda/discovery.
The /proc/*/irda files are:
___________________________________________________________________
root@duckman:~# ls /proc/sys/net/irda/* /proc/net/irda/*
/proc/net/irda/discovery /proc/net/irda/irlmp /proc/sys/net/irda/devname
/proc/net/irda/irda_device /proc/net/irda/irttp /proc/sys/net/irda/discovery
/proc/net/irda/irias /proc/sys/net/irda/compression
/proc/net/irda/irlap /proc/sys/net/irda/debug
___________________________________________________________________
· It is also possible to debug the code. But I don't know how to do
this. If you want to use SKB debug code, you may edit irda.h and
change /include/linux/skbuff.h (see revision history of snapshot
10-2-98).
· For problems with the irda module a utility from the modules
package kdstat might be helpful. But I was not able to try this.
· "You can now alter the number of discovery packets used (1, 6, 8 or
16) and the timeout between sending them (2-8 * 10 ms) in
/proc/sys/net/irda. Please experiment if you have problems
discovering your device. My Palm III seems to like 16
discovery_slots and 8 (*10 ms) for slot_timeout. " ... "The
absolute minimum for reliable discovery of the IR-610 seems to be
9."
· If anybody gets a kernel Oops, then please feed it to the
../linux/scripts/ksymoops/ksymoops program, so that we can find out
where it went wrong. Just cut out the Oops lines from the syslog,
save them to a file, and then run ksymoops <file>
· Dag Brattli wrote: I found out that the cs4232 sound card was
giving me several hundred interrupts per second! I removed the
sound stuff from my kernel, and the machine is now generally about
4 times faster!
Linux/IrDA may get problems if you are running the esound server
(esd) on your machine. Both my machines, a 166Mhz Pentium laptop
and a 200Mhz Pentium Pro cannot run Linux/IrDA when esd is running.
The reason is that esd makes the soundcard give interrups over 300
times/second which makes the serial driver overrun when receiving.
This is because the serial driver now uses slow interrupts in
Linux-2.2 (everything is slow interrupts in 2.2), so the interrupt-
handler schedules on its way out. The good thing about slow
interrupts is that packets are delivered much faster, since you
don't need to wait for the next timer-tick. The only exception for
this is the pc87108 driver which works fine since it uses DMA and
will only give a couple of interrupts per packet.
11. Known Bugs
If you find a bug, please send a bug report to the mailing list,
including dmesg output, and which Linux version, and hardware you are
using. Thank you!
Sometimes IrCOMM fails to connect (especially when both devices
discover each other. You can disable discovering with echo 0
>/proc/sys/net/irda/discovery)
A CR (carriage return) character cannot be transfered between two
linux boxes via IrCOMM with cat file >/dev/irnine and cat /dev/irnine.
It causes a strange thing and freezes your Linux box. Compiling the
pc87108 device driver non modular crashes the kernel on boot.
Temporary solution: compile the driver as a module
IrOBEX may eat some data on receive. The bug is most probably in the
user-space side of IrOBEX.
12. FAQ
· Q1 - Question: I do not know anything about ports and irqs. What
should I do?
· Answer:
PART A: Hardware settings
- 1 Have a look at your hardware specs!!! If not available look at
the support page of your vendor, or contact the support hotline.
You might also find the information in one of the hardware
overviews mentioned above.
- 2 Use a current BIOS. Usually available at the support page of
your vendor.
- 3 Try setserial /dev/ttyS? -g -a | egrep 16550A. One of the
shown devices is probably the one you are looking for. Usually it
is the second one, but with no guarantee.
- 4 Note: What seems like an UART is physically the IrDA
controller. For my HP Omnibook 800 this is the VLSI VL82C147 PCI -
IrDA controller. These controllers should behave up to 115 200 bps
like UART's. But sometimes it is very difficult to get the right
configuration.
PART B: How to tell the kernel about the hardware settings
-4 cat /dev/ioports to see which ports are already in use.
-5 cat /dev/interrupts to see which interrupts are already in use.
-6 Make ports and interrupts available for use with the IR device,
e.g. stop the pcmcia service or include a line like this in
/etc/sysconfig/pcmcia: PCIC_OPTS="irq_list=3,4,5,7,9,10,12,14,15"
-7 Now try to guess what the right interrupt and port is. Use
setserial /dev/ttySx irq M port 0xNNNN to tell the kernel. If there
is more then one possible chance try them all (Note: As mentioned
in the Serial-HOWTO you should not try irq 0, 1, 6, 8, 13, 14).
-8 If you were successful please send the useful parameters to the
author, because I would like to include them in the hardware
overview.
-9 Good luck.
It might also be necessary to fine tune the IR serial port with
setserial, e.g., setserial /dev/ttyS0 spd_vhi (speed rate 115200).
· Q2 - Question: For me, irattach hangs, but recognizes the printer.
/var/log/messages shows that irattach found my HP LaserJet 6P.
· Answer: The "hang" is normal for irattach. Everything is working
right if you see the HP Laserjet show up in the log. "hang" means
irattach is polling the IrDA-Devices for incoming connections. If
you kill it with <CTRL C> the irattach program crashes and
/dev/ttySx does not work anymore. The problem is within the irda
module, and not with the irattach program. Rebooting is the only
thing to do! Next time put irattach in the background by using
irattach &. Stop it if necessary with killall irattach.
Recommendation by Andreas Butz: To my knowledge, <CTRL Z> bg should
work, too, but I haven't tried it in this specific case. Normally
it has the exact same effect as appending & to a command.
· Q3 - Question: I get a message like tcsetattr read/write error in
/var/log/messages.
· Answer: Caused probably by wrong /dev/ttyS* or wrong irq or port.
· Q4 - Question: Every setting seems alright, because I get the
appropriate messages. But it still does not work.
· Answer: Move the devices to within 0.5 meter (1.5 feet). Check that
only one application is using the infrared port. Check that both
devices are using the same protocol, such as IrOBEX or IrCOMM.
· Q5 - Question: I have downloaded the latest snapshot, and compiled
it successfully under Linux 2.0.33 running on an IBM Thinkpad 560E.
In the absence of any other IrDA machines to test with, is it safe
to assume that once the module has been inserted and the syslog
reports "irattach: Serial connection established.", is the IR
really working, and will it start to respond once there is another
machine with which to talk?
· Answer by Dag Brattli: Sorry, this only means that irattach has
done its part of the job, which is just to start the irda-tty.
Maybe the message should have been different, but as I said, it
tells that the serial connection between the irda-chip and the
irda-driver is established.
Note: Support for IrDA on 2.0.x kernels has been discontinued. You
are encouraged to switch to 2.2.x kernels and use the newest IrDA
patches available at http://www.cs.uit.no/~dagb/irda/snapshots/.
· Q6 - Question: At startup modprobe -a checks /lib/modules/<KERNEL-
VERSION>/net/irda.o and causes the messages: "IrLAP; Missing IrTTY
/IrLMP Error no IrLAP connection" (in /var/log/messages and on the
console).
· Answer by Werner Heuser: Workaround for SYSTEM V style systems: Put
a script named for example "ir_rmmod" containing
______________________________________________________________________
#!/bin/sh
echo "$0 : remove irda module"
rmmod irport.o
rmmod irtty.o
rmmod irda.o
______________________________________________________________________
in the startup process (/etc/init.d and a symbolic link name for exam&SHY;
ple "S100ir_rmmod" in /etc/rc3.d to "ir_rmmod"). (Verify the path for
"sh"). For BSD style systems try the corresponding approach.
· Q7 - Question by Ho Chin Keong: Is there other way of setting up
communication between the 2 laptops besides setting up a LAN route
between the two?
· Answer by Dag Brattli: Yes and no! One of the IrDA standard, IrCOMM
permits you to emulate a serial cable between two laptops, so you
can use any application written for serial ports (terminals, PPP,
slip, etc.). This is however not yet implemented in Linux/IrDA. The
IrLPT (printer) support is actually a subset of IrCOMM, so some of
it is working!
· Q8 - Question by Ho Chin Keong: If I block the infrared path
deliberately for more than 10 seconds, the connection could not re-
establish. I have to kill the irattach and restart the whole
procedure to start the infrared route. The connection could be
maintained, however, if the blocking is less than 10 seconds. Is
this part of the design or a bug? Is there any way whereby we can
lengthen this time limit from 10 s to longer or infinitely?
· Answer by Thomas Davis: This seems to be a bug in the primary side
of the IrLAP/IrLMP code. It appears not to send the
reset/disconnect notice all the way back up the stack. You'll
notice it when IrLPT gets stuck in the query mode while you were
trying to talk to a printer, and disconnected/interrupted it when
it was handshaking. (and now, it shows up in the IrLAN portion)
· Q9 - Pierre-Guillaume Raverdy asked: Should I update to IR lib on
my palm and update the system to version 3.0.2?
· Answer by Dag Brattli: You should not need to update your Pilot,
but it should not do any harm to do so. It is however required if
you want to use the IrCOMM library from IsComplete
· Q10 - Pierre-Guillaume Raverdy asked: Also any simple source code
(especially on the palm side) would be greatly appreciated.
· Answer by Dag Brattli: Get the Pilot SDK from Palm. Unzip the
examples.zip and take a look at the beamer application.
· Q11 - Kai Poehlmann wrote: I have a gsm-phone from Ericsson SH 888
and a linux-computer without an irda-port. I have heard that
Ericsson wants to talk with the phone the IrDA-protocol also when
using the serial cable... :-/ Is it now possible to use this phone
with this IrDA-port for linux and the cable?
· Answer by Matthias Lemke: Yes its possible. I tried it 6 weeks ago.
But i had same problems like with real-irda. I can connect my
phone. i can reset it by ATZ but after ATDT nothing happens. Same
with cable or without. But i think you should test newer versions
of the port.
· Q12 - Jonah Peskin wrote: Has anyone had any success extending the
range of an IrDA transceiver? I'm using a Dell Inspiron 7000
notebook, and it seems to have a receiving range of about 1 meter.
I realize this fits the IrDA spec, but are there any laptops or
devices that can do better than a meter? Why not just get a 1 meter
cable?
· Answer by tzeruch@ceddec.com:Because manual connection (until
things like the Palm Cradle) is cumbersome and time consuming and
often creates problems (accessing the back side of my desktop
requires contortions).
The main problem is that you generally have to make the receiver
more sensitive. Basic physics has the inverse square law: the
intensity drops with the SQUARE of the distance, so going from 1 to
5 meters requires 25x the power (and battery drain on a portable
device), or 25x the sensitivity (and dynamic range - it still has
to be able to work at 3 inches). And if you want to do it on the
other end, it doesn't simply have to be 25x more sensitive, it must
pick up the tiny IrDA pulse needle in a haystack of florescent
lights, screen savers, moving shadows...
Someone tried it with a Palm III upgrade board: http://home.t-
online.de/home/PSPilot/ppppiii.htm
13. Infrared Remote Control
13.1. Resources
Remote control via infrared is not the aim of the Linux/IrDA project
but is included in this HOWTO to cover "Linux and Infrared" more
completely. I found three projects which worked on this topic. You may
find some links to current information at http://
www.snafu.de/~wehe/index_li.html.
· LIRC LInux Remote Control
LIRC is a package that supports receiving and sending IR signals of
the most common IR remote controls. It contains a device driver for
hardware connected to the serial port, a daemon that decodes and
sends IR signals using this device driver, a mouse daemon that
translates IR signals to mouse movements and a couple of user
programs that allow to control your computer with a remote control.
Takahide Higuchi wrote about LIRC: "It's great, and it seems almost
complete solution, but it seems there is almost nothing supporting
hardware on the market (or need to solder some special circuit ...
it is hard work for many people to do so). I believe that LIRC will
be more popular if consumer IR support is implemented in FastIR
drivers and some common API (for example, a raw IrSocket and common
ioctls) is made!". You may find LIRC at http://www.thp.uni-
koeln.de/~rjkm/lirc/
· Serial Infrared Remote Controller
This is a simple, cheap device that can be connected to any serial
port to control most components that have infrared remote controls.
It was designed and built on a solderless breadboard and is finally
designed as a PC board. You may find this package at
http://www.armory.com/~spcecdt/remote/remote.html
· Infrared Tools for the COREL Netwinder PC
Ryan Shillington wrote some tools to control the COREL Netwinder
via infrared, for example:
Server Side for the Corel Palm Administrator (deamon). It depends
on having ir-simple installed and up and running. With this you can
check and change IP addresses, Gateway addresses, setup eth1, etc.
You can also run simple commands AND you can check the Temperature,
Memory, Load averages, etc.
Client Side for the Corel Palm Administrator. You can also run
simple commands AND you can check the Temperature, Memory, Load
averages, etc.
A very basic Infra Red device driver. This does not support IrDA
(only unreliable transfers). It looks specifically for Remote
Control signals (and Keyboard, etc.). It blocks and passes data up
very differently.
You may find the tools at http://www.netwinder.org/~ryansh/
13.2. Infrared Remote Control - IrDA
Two of the above mentioned projects use some kind of selfmade dongle
for infrared remote control. There is also a description to build a
serial IrDA dongle by yourself in the german ELEKTOR 5/97 p. 28
magazine. Maybe someone can merge these two kind of dongles together.
For a discussion of the relation between Infrared Remote Control and
IrDA I quote from the Linux/IrDA mailing list (shortend and modified
by wh):
Ryan Shillington wrote: "Remote IR and ASK-IR are very different from
FIR or MIR or SIR.
Remote IR and ASK-IR are very low speed and low frequency (but very
long range) uses for IR. They operate around 2400 baud.
SIR operates at higher rates, and is meant for long range transmission
where you need more than a few characters pass through (unlike a
remote control).
MIR is a little faster (less range), but with speeds up to 1.15 Mbps,
and FIR (where the devices have to be practically touching) is 4Mbps.
The range is inversely proportional to the speed you can send data at.
I'm working on drivers for Remote-IR, but you should know that your IR
stuff has to support it. Look for protocols like NEC, RC-5 or RC-0
(those are the most common ones).
You can use SIR to receive Remote Control signals. Set your baud rate
nice and low and data will come through. BUT, from my experience, it's
not the RIGHT data. It's not being analyzed in the right way, and as
such, you can't compute the checksums or check it with its complement.
I have managed to get data in (using SIR) with remote controls. I
have been told that SIR will read the remote control stuff differently
depending on temperature (although I have never had that experience).
"
Lichen Wang <lwang1@ix.netcom.com> wrote in response: "The so-called
ASKIR in most laptops etc. is not meant for remote IR devices. ASKIR
is meant for Sharp Wizard and Zauaus PDAs and some of Sharp's notebook
PCs. Sharp stated this long before IrDA was established and is still
supporting it to maintain backward compatibility. Apple's Newton had
this capability at one time, too.
Briefly, ASKIR uses 9.6 Kbps (19.2 and 38.4 Kbps are also possible)
asynchronous data format of 8 data bits, 1 stop bit, and odd parity.
The "start" bit as well as all 0 bit in data/parity are transmitted as
IR square wave at 500 KHz (DASK sub-carrier). The "stop" bit as well
as all 1 bit in data/parity are represented by the absence of any IR
transmission.
As you can see, this is totally incompatible with exiting IR remote
control.
[..]
True. Not only can you use SIR hardware to receive, you can transmit,
too. Of course, there are some limitations.
Most IR remote controls use 38 KHz sub-carrier. 3 times 38 is 114,
very close to 115.2. You can set the UART to operate at 115.2 Kbps, 7
data bits, no parity, and 1 stop bit - a total of 9 bits. Each 3
cycles of the 38 KHz sub-carrier can be received or transmitted as a
byte of 0x5B.
There are some physical limitations in addition to the fact that the
sub-carrier must be 38 KHz. The SIR receiver is not as sensitive to 38
KHz as the IR remote receiver designed for that. The SIR transmitter
has a much lower duty cycle and thus can not emit a strong sub-carrier
either.
IR remote encodes the control signal by turning on and off the sub-
carrier at certain specific patterns. Now that you can transmit and
receive the sub-carrier, what remains is all in timing.
For transmit, you have to know how many consecutive bytes of 0x5B to
send for each burst of the sub-carrier, and how long to be quiet
between the bursts.
For receive, you have to know how many of the 0x5Bs you received are
consecutive, and how long the gaps were between these groups of
consecutive bytes.
[..]
My experience with the IrDA link distance of SIR, MIR and FIR is
somewhat different from what Ryan said.
[..]
SIR, MIR and FIR should all work from 0 to 100 cm but in practice:
(a) Some devices may have problems at LONG distances.
When possible, place the two communicating devices no more than 50 cm
apart. Low power devices, such as Pagers, Phones, etc. may have even
shorter ranges despite the fact that they use SIR instead of MIR or
FIR.
(b) Some devices may have problems at SHORT distances.
Place the two devices at least a few cm apart. Putting the two devices
too close to each other can cause troubles.
It is somewhat intuitive that when the link is not reliable we put the
two devices closer together. But it is counterintuitive that too close
is not good either. The reason is that the light intensity at 1 cm is
10.000 times brighter than that at 100 cm. At 0.5 cm, it is 40.000
times, etc. The IR receiver manufacturers have difficulties to cover
this huge dynamic range. We all have problems reading under a 10 W
light bulb, but imagine how it feels under a 100.000 W light!
[..]
The IrDA Physical Layer is totally incompatible with the DASK
modulation used in IR remote controls. Thus it is not possible to use
the same controller function for both FIR and remote control. However,
practically all FIR controller chips do include some additional
functions to support remote control. National, SMC, and Winbond (just
to name a few) all have such I/O chips.
The IR transmitter for FIR and remote control are very similar. I have
tried a standard FIR transmitter. It can reach 10 meters for remote
control purpose. Thus it performs just as good as transmitters
designed for remote control.
The IR receiver for FIR and remote control are somewhat different. A
FIR receiver can receive remote control signals but can reach only 1
meter whereas receivers designed for remote control typically can
reach 10 meters.
I have an ISA bus adapter with a National I/O chip that supports both
FIR and remote control. I also have IR Dongles that include both FIR
and remote control receivers. (Plus a transmitter for both modes.) I
cannot find any software to support remote control functions. I did my
own experiments in DOS (I cannot run Linux yet.) Anybody interest in
this? "
Benny Amorsen wrote: "I have a laptop that is supposed to support
ASKIR. The mode of the infrared port can be switched to ASKIR in the
BIOS. Having to reboot to switch the mode in the BIOS makes it
useless, though, so someone would have to find a way to switch on the
fly. "
Dag Brattli wrote: It should be possible to use IrControl (formerly
IrBus) for IrDA compliant remote controls. I currently don't know
about any remote controls using IrControl standard, but there should
be some out there (anyone else who knows better?). You should go to
the IrDA site (http://www.irda.org) and get the physical layer
standard (which includes IrControl I think).
"Normal" IrDA (using IrLAP) is _not_ well suited for remote control
because of the connection oriented nature (and just supports 9600bps
for connectionless use). The reason for the limited range is eye-
safety they say (but I currently don't know why CIR works better using
the same power). I have however seen laptops connect at 4-5 meters
(but I don't think that any high speed communication would be
possible).
Most IrDA chipsets are capable of CIR operation, and it is quite easy
to modify the drivers so they talk CIR. Takahide Higuchi has started
to look at IrSockets and it would be great if we could open a "raw"
Ir(DA) socket which then could send and receive CIR packets. Then all
the CIR applications could live in userspace.
I know that Corel is interested in using CIR for controlling the
NetWinder (and they actually have running code). Take a look at
http://www.slashdot.org/articles/98/12/05/0916216.shtml or
http://www.netwinder.org/~ryansh
14. Infrared and Eye Safety
This section summarizes some ideas and thoughts that were exchanged on
the Linux/IrDA mailing list. It is not medically wellfounded, and
whoever has better evidence or some more wellfounded source of
information is encouraged to contribute it to this HOWTO.
The IrDA spec says that the range of IrDA devices has been limited to
1m for reasons of eye safety. Another plausible assumption is that
power consumption and IR pollution/crosstalk were reasons for this
limitation. In principle there could be danger for the eye, because
infrared light is not registered by the eye, and thus the pupil won't
close in order to protect the retina from bright IR light sources.
This is the same situation as with UV light, which will cause snow
blindness eventually, but in contrast to UV light, IR light contains
much less harmful energy due to its longer wavelength.
The only legal restrictions and medical advices we were able to find
on the web were concerned with infrared emissions of heat lamps or in
the welding process. This suggests that IR light as emitted by IrDA
devices will be harmless, since even the peak power emitted by strong
IR LEDs (ca. 300mW) is several orders of magnitude below the power
emitted by medical IR heat lamps (up to 500W). For these, however, you
are supposed to wear protective goggles, so maybe if you are looking
straight into 1.000 infrared LEDs flashing at once, you should do so,
too. The effect of infrared light is mostly heat, though, and not an
alteration or destruction of the biological cell structure, such as
caused by UV light. Though in the specs for the HP OmniBook 800
Hewlett-Packard recommends not to look directly into the IR LED.
As stated above, this discussion is only based on guesswork and common
sense assumptions about the data found in IR LED and heat lamp specs.
If anybody with a better medical knowledge can comment on this, please
do so!!!
15. Credits
Thanks to:
· Dag Brattli - Linux/IrDA core team
· Thomas Davis - Linux/IrDA core team
· Takahide Higuchi - Linux/IrDA core team
· Ralf Zabka
· Benny Amorsen
· Lichen Wang
· Ryan Shillington
· Richard Titmuss
· Fons Botman
· Rui Oliveira
· Jon Howell
· Carlos Vidal
· Joonas Lehtinen
· Markus Schill
· Bjoern Hansson
· Pawel Machek
· Ho Chin Keong
· Bjoern Mork
· Andreas Butz
· Tang Ning
· The members of the Linux/IrDA mailing list.
· The writers of the other HOWTOs which gave me many inspirations.
· The developers of the SGML-Tools which provided some means to write
a HOWTO.
Sorry I didn't start to follow the credits when starting the HOWTO,
so probably I forgot somebody.
16. Revision History
· v0.1 to v0.4a, 19 March 1998 to 4 August 1998, drafts, not included
in the LDP
· v1.0, 14 August 1998, release to the LDP
· v1.1, 18 August 1998, added info about IrCOMM patch by Takahide
Higuchi, minor changes
· v1.2, 24 August 1998, updated to linux-irda-1998-08-20 snapshot,
added FIR section and revision history, minor changes
· v1.3, 27 September 1998, added sections about multiple instances,
cellular phones, digital cameras,Linux to Linux connection, the
cutting edge - CVS, power saving; some changes in general
configuration section, changes in hardware overview section, minor
changes
· v1.4, 11 October 1998, better description of IrCOMM support,
changes in dongle connection section, changes in Palm III section,
minor changes
· v1.5, 12 October 1998, minor changes
· v1.6, 26 October 1998, section about IrManager added, updated to
the linux-irda-1998-10-21 snapshot, changed dongle connection
section, minor changes
· v1.7, 1 November 1998, added remote control section, changed dongle
connection section, minor changes
· v2.0, 9 January 1999, nearly complete rewrite and rearrangement
according to the new structure of Linux/IR which is included into
the kernel since 2.1.131, added info about BIOS support into dongle
connection section, configuration tool section and CVS section
removed
· v2.1, 13 January 1999, minor changes
· v2.2, 26 January 1999, project name changed from Linux/IR to
Linux/IrDA, extended the Troubleshooting chapter, changed the order
of the Known Bugs chapter after the Troubleshooting chapter,
removed some lint
· v2.3, 4 February 1999, added chapter about Eye Safety written by
Andreas Butz; spell checking, reworking of Kernel Parameters
chapter and additional information by Andreas Butz; minor changes
· v2.4, 9 February 1999, changed information about applying a patch
file
17. Copyright and Disclaimer
Copyright © 1998, 1999 by Werner Heuser. This document may be
distributed under the terms set forth in the LDP license at
http://metalab.unc.edu/LDP/COPYRIGHT.html.
The information in this document is correct to the best of my
knowledge, but there's a always a chance I've made some mistakes, so
don't follow everything too blindly, especially if it seems wrong.
Nothing here should have a detrimental effect on your computer, but
just in case I take no responsibility for any damages incurred from
the use of the information contained herein.
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