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 example "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