Hi. Complete Arduino novice but have project in mind for which Arduino seems ideal. Before I purchase can I just confirm that it would be possible to use a serial to USB converter (I have no serial port) and still have Java recognise the inputs from Arduino? If not is there an alternative as I'm not sure there is an appropriate Java API for USB detection on Windows XP. Sorry if it's a trivial question, and is probably more suited to a Java forum but thought I would start here. Thanks
You don't even need a USB-to-serial converter since the Arduino is a USB-connected peripheral. It will LOOK like a serial port as far as your computer is concerned, but the hardware is all USB.
And there should be no problem recognizing the inputs from the Arduino with Java. The Arduino GUI, as a matter of fact, is written in Java and has a built-in serial terminal program that communicates with the Arduino over the "serial port".
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Appreciated. Many thanks. Time to order!
I am running XP in a partition on my Mac and it recognizes the Arduino just fine. I may have had to install the driver that comes with the distribution, but that's all it took if so.
I think you need to be more specific about what you wish to do.
would be possible to use a serial to USB converter (I have no serial port)
This sounds like you have a PC that only has USB and so you want to use USB on the PC.
I'm not sure there is an appropriate Java API for USB detection on Windows XP.
This sounds like you want to use Java on the PC but you are not sure if you can use USB from Java, so you are kind of contradicting yourself.
The Arduino has a development environment that runs under XP and allows you to download code to the Arduino over USB.
It is possible to open a monitor window and receive output back from the Arduino over USB, I cannot see any reason why your own program could not do the same thing.
I think the Arduino has a UART (have not got that far myself yet) so you could probably also attach a serial to USB converter to that and plug the USB end into the PC. You would need to be clear about voltage levels and how things get powered, but I am sure people here will advise.
I would be very surprised if Java does not support USB under XP. Having said that a quick google did not give a lot of confidence 
Like I said I think you need to give a bit more detail about what you want to do.
Go with what RuggedCircuits is saying it sounds right and he obviously knows more about this than me.
The Ardino is very easy to use and good fun by the way.
Thank you all. radman - you are right, I should have given more details. I'm attaching a rough schematic for the project. Based on responses so far I'm happy that it should be ok. All I need Arduino to do initially is to receive signal and pass to PC (see notes on schematic). I'm aware of possible timing lag issues but I hope they can be resolved by comparative measurements.
Thanks again.
TimingSchematic.doc (30 KB)