Ok thanks so much!

Hi,
I have an Arduino UNO and this sample sketch:

Code:

void setup(){
  pinMode(4, INPUT);
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop(){
 if(digitalRead(4)==HIGH){
   digitalWrite(13, HIGH);
 }else{
   digitalWrite(13, LOW);
 }
 Serial.println(digitalRead(4));
 delay(100);
}

Is it normal that the UNO reads high input value on input 4 as soon as I connect a wire to the input? The wire is floating, not connected to anything!
Did I break the atmega???  :-[

I have found this page:
http://www.ladyada.net/make/xbee/wiring.html
where is the RTS line on an Arduino UNO?
I tried to connect the pin #16 of XBee (RTS) to the same point of the photo, on the solder, but it could not update the firmware...

Nobody?
And if it is not possible, is it possible at least to update the firmware with the arduino as a usb/serial translator doing the necessary connections, but without the xbee shield?
Any help?

Is it possible?
I can change settings in the xbee modules while installed in the arduino shield, but I cannot update the firmware.
Any hint?

At last, here is the truth! Here is the reason!
Thanks so much.

Hehe yes you are right.
That thing sounded strange, because I know Massimo Banzi is one of the maker of Arduino.
Thank you!!

Thank you!
I asked you this because I noticed a strange thing in a text guide (getting started with arduino - by massimo banzi). In an example, the author puts a led directly between pin 13  and GND, on the board itself, with no resistor at all...  :o

Thank you
Actually I don't know the voltage drop of a LED and the desired current in the LED. Are these standard value for a colored LED?

Hi. Really simple question.
I want to connect simple colored (yellow and red) LED to the digital output of arduino Uno.
The voltage of the digital out as we know is 5V: wich resistance should I use?
Thanks

I made it,
the iphone receives data from Arduino, i can see it in terminal.
Now the tricky part is... I need to access this serial stream from inside an objective C application.
I just need to cach a single character once a minute (that's the reading of a digital sensor connected to the arduino).
Any help about it?

something like:

°  Arduino

|  1k res

° iPhone

| 1k res

° ground

?

Ok that's enough for me at the moment, since I just ordered the breakout connector and cannot work right now.
I will try to do that when I will be able to get the physical connection.
So 1K resistance from arduino to iPhone is enough or it is not so safe?

Thanks everybody for this really useful thread.
I just can't get a point. Once you menage to have a funcitonal serial comunication, is there a way to access these data using XCode?
I need to develop an app that uses some of the iPhone sensors (GPS, accelerometers) together with the sensors connected to the arduino, and I need to store all these data on the device.
Is it possible, to access to the serial flow from inside a regular XCode app?
Thanks so much