The docs seem to indicate that you need a resistor to hook up
an LED except on pin 13.
The photo shows a diode connected directly to pin 16.
One or the other is wrong, right?
Your URL in the subject field was chopped off. Were you talking about the ArduinoMini?
If so, is this the picture you were trying to indicate?
The pin numbers are not counted like a plain DIP. If you used a traditional counterclockwise count from the upper right corner, you might think that LED was on "pin 16." The name for that pin is "Digital I/O Pin 13," and it has a resistor on the board ready for this exact usage. See the pin-out descriptions.
On larger boards, the same numbering is used for the pins on their headers as well.
Pre-diecimila, pin 13 had a resistor before connecting to the connector, but it went away when the design started putting the "pin 13 LED" on the board (with its own resistor) instead of requiring the user to add it (I forget whether this was NG or Diecimila.)
So with any "modern" arduino, you should use a resistor with your LED no matter which pin you connect it to.
On the other hand, it seems to be pretty safe to connected LEDs directly to AVR pins without any resistors at all; current doesn't go TOO far above safe limits for either LED or AVR. It's not "recommended practice", though.
Yes, I was talking about the mini.
I assumed the numbers on the board corresponded
to the pin numbers. You know what they say about
assume.
Good to know before I wreck something.
It may be worth not putting actual (inapplicable) pin numbers
on the mini circuit board.
Thanks.
It may be worth not putting actual (inapplicable) pin numbers on the mini circuit board.
I know it's really confusing, but the little "1" is the only "pin number" I see in that photo. It corresponds to the TX (transmit serial) pin in the corner, which actually is named and labeled "Digital I/O Pin 1" on larger boards.
The pin next to it (which you'd think is the second pin) is named "RX" aka "Digital I/O Pin 0." The "Digital I/O Pin 2" is further down, after the power pins. This strange arrangement (and rearrangement) of the first three or four pins allows a common four-strand jumper cable to interface with the serial interface.