Using generic IR ports for RCX 1.5

[traltixx]

Hi,
I can't find my lego mindstorm IR tower and I was thinking if it is possible to hack a generic IR dongle ( http://www.usbgear.com/computer_cable_details.cfm?sku=U1-FIR-IRDA&cats=139&catid=139 ) from a computer so that it can communicate with the RCX brick. Is that possible? How do I do this?
Thanks

[Steve Hassenplug]

I've seen many people attempt this, but none who have succeeded.  (but
I won't say it's not possible)

Steve


On Wed, Feb 4, 2009 at 11:04 PM, traltixx <lego-robotics@...> wrote:

>
> Hi,
> I can't find my lego mindstorm IR tower and I was thinking if it is possible
> to hack a generic IR dongle (
> http://www.usbgear.com/computer_cable_details.cfm?sku=U1-FIR-IRDA&cats=139&catid=139
> ) from a computer so that it can communicate with the RCX brick. Is that
> possible? How do I do this?
> Thanks
>
> --
> View this message in context: http://www.nabble.com/Using-generic-IR-ports-for-RCX-1.5-tp21844970p21844970.html
> Sent from the LEGO Robotics mailing list archive at Nabble.com.

[Claude Baumann]

In lugnet.robotics, Steve Hassenplug wrote:
> I've seen many people attempt this, but none who have succeeded.  (but
> I won't say it's not possible)
>
> Steve
>

IrDA works quite differently from what the RCX is capable of understanding
normally under usual firmware. I don't think that you can change the dongle
reactions, since on the physical layer it will work according to the IrDA
specifications. The only way to set up a communication with the RCX would be to
write an own bit-banged driver for RX (RCX side). The main issue is that you
cannot use the normal serial RX interrupt function, because the IR-receiver
(Vishay TSOP 1738) reacts in direct function of the presence or absence of a
38kHz IR-signal, although it also reacts in the presence of a single infrared
pulse. More specially, it will be difficult to detect the start and the stop
pulse.

Probably the RCX-TX side could be solved much easier, because you only need to
cut off the infrared signal after the short IrDA required pulse, or control the
RCX IR-LEDs directly. (Note that doing this is not without risk for your RCX. If
by inadvertance you switched on "long range" and pulsed the LEDs for a longer
duration (I mean here milliseconds), then the high current can burn either the
LEDs or the driving transistors. I have done both, so be aware. After this your
RCX is dead, because it can no longer communicate.) Anyway, you will need a
tower to download your new IrDA driver to the RCX!!, or hack the RCX to have a
hardware serial connection. You will also need to patch the firmware or program
on the lowest level.

You can consult http://www.emesystems.com/BS2IrDA.htm#IrDA, if you want to see
how an IrDA application is made.

We have realized a lot of infrared communication devices with the RCX. The last
time during the HALE project http://www.convict.lu/htm/rob/hale.htm. If you are
equiped and skilled to build your own microcontroller electronics, then it is
quite simple to realize a serial replacement tower for the RCX. You will need an
USB/RS232 converter. If you cannot do that, I'd recommend that you try Ebay for
another tower.