moi,
I want to trigger with a bang from PD a LED that is connected to my notebook via an Arduino board.
so every time the LED receives a bang its light should turn on for a short moment.
how to do???? anybody an idea??? or experience???
and yes...I use widnows xp.

I don't have an ardunio board here but afaik you need a logic level, 1 or 0, to activate the LED. If you send 11111111 (255) to an 8 bit port all the LEDs will light, then send 00000000 (0) to the port and they will all go off.

To convert a bang to a brief logical high something like

[bang(
|
[ t b b ]
| |
[del 250] |
| [255(
[0( |
\ /
\ /
\ /
\/
[send yourardunioport]

may do the trick

thanks,
but my problme is how to create a working communication between PD and the Arduino board.
what you were calling [sendyourarduinoport] is the connection I don´t have at the moment.
hmmm. whatcha gonna do????

look at Hans tutorials

http://www.arduino.cc/playground/Interfacing/PD