Voltage of I/O pins on Duemillanove

I would assume the digital I/O pins operate at 5V (so as to interface with most ICs). Is this correct? I need to know so I can calculate resistor values for LEDs on these pins.

Yes that is correct when a pin is high, it is approx. 5 V

The I/O pins output a high voltage about equal to the supply voltage wired to the processor chip. Most common Arduino boards use +5vdc, but some small breadboard/stamp module models use 3.3vdc.

Lefty

I ordered a Duemillanove, so I'm assuming then it will be about 5V. This is good. Now that I've calculated the resistance needed for my LEDs, I can place my component order (about 80 bucks worth of toys ;D)

I can place my component order (about 80 bucks worth of toys)

You will realise once you get into arduino that \$80 of stuff is not that much and you always want something else :D

I have purchased more than \$300 of stuff or something like that in the half a year that i've been doing arduino stuff. I have also used a lot of second hand (free stuff) in projects, so make sure that if you see something, you take it because you will want a big bits box to take things from for future projects ;)

Anyway, hope you enjoy arduino. Out of interest, what stuff have you purchased?

Mowcius

LEDs, caps, pots, resistors, dip switches, 555 timers, off-mom switches, 4051's, and some terminal strips. I also picked up a few items for PCB etching (I'll probably build a UV LED box for photoresist in the next week or so). My interest in electronics isn't Arduino specific, but coming from a computer science background, it's nice for circuits involving logic (sure beats boolean algebra and a bunch of NAND gates).

sure beats boolean algebra and a bunch of NAND gates

Sure does!

Mowcius

I would assume the digital I/O pins operate at 5V

Or 4.75 volts when its hooked up to my computers USBâ€¦

The data sheet says that if the chip is being powered by 5V and is supplying 20mA then the minimum high level output voltage is 4.2V.