[clug] how to configure a second keyboard

Robert Edwards bob at cs.anu.edu.au
Sun Nov 11 23:31:24 GMT 2007

Hi Michael,

Many thanks. Alas, I was already aware of that reciever implementation -
I was thinking that you had a receiver that was actually working over
the serial protocol (and hence would work with many other serial ports).
This one is the usual "bit-banging" on the Data Carrier Detect (DCD)
serial handshaking line.


Bob Edwards.

Michael Cohen wrote:
> On Mon, Nov 12, 2007 at 09:22:36AM +1100, Robert Edwards wrote:
>> Michael,
>> More details on your serial IR receiver - please!
>> Cheers,
>> Bob Edwards.
> Bob,
>   The serial receiver i built was the one described in
> http://lirc.org/receivers.html and the layout I used was in
> http://lirc.org/images/irrcv_board.gif. It probably took about 20
> minutes to build the first one the next one took 10 minutes etc... (I
> built 3) I think the total cost was less than $10 - the IR component
> - most expensive part - cost about $2.60 from RS.
> There are other references like
> http://lnx.manoweb.com/lirc/?partType=section&partName=circuit which try
> to build it into the connector but thats just silly because the serial
> connector is at the back of the computer and the receiver has to be in
> the front so you need to make a serial cable anyway. That reference is
> excellent for the software configuration part though (i.e. using xmode2
> and irrecord).
> I find that you need to be quite specific with the lirc driver (which
> you need to compile from source as explained in the lirc reference) -
> and set stuff which may be autodetected wrongly. This is what I do in
> rc.local: (btw by setting the io and irq you dont need to recompile if
> you change them later - most lirc packages have a gui for configuration
> but that only configures the defaults and is not needed if you
> explicitely set it like this).
> setserial /dev/ttyS0 uart none
> modprobe lirc_serial io=0x3f8 irq=4 sense=0
> /etc/init.d/lirc restart
> I find that it takes a little while for the receiver to become ready
> (i.e. respond properly) maybe 10 seconds or so - that might be due to
> the RC factor on the power regulator taking a while to bring the supply
> voltage up if the serial port current is too low (this might be specific
> to my mobo).
> If your receiver has the sense autodetected wrong it will work really
> badly - i.e. you can train it but the training will not be that stable
> and will miss many signals which is why I force it now. Often I find
> that stray light does affect the receiver (I think it might increase the
> voltage bias) so try to put it in a reasonably dark spot. The workable
> range with my remote is about 10-15 meters.
> This receiver works well - but your mobo _has_ to have real serial ports
> not usb/serial - that wont work. One of my new mobos doesnt even have
> any serial ports at all - so that makes life more difficult.
> You can use a PIC to build a usb receiver but thats beyond the time i
> care to invest on it atm. There is a reference for an IR receiver which
> uses the sound card which might be nice if anyone got that one to work?
> Michael.

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