[dorkbotpdx-blabber] Just a question re: Dorkboard

[Donald Delmar Davis]

The led on the dorkboard (and the arduino in general) is connected  
from the supply to the pin through a resistor.
The pin sinks the current so LOW is on.

On Jan 26, 2009, at 9:25 AM, Aaron wrote:

> Hello, just got done with the induction yesterday, and playing with my
> dorkboard today.
>
> I hooked an additional LED up to pin 12, and am playing with modifying
> the little blink program.
>
> int ledPin = 13;                 // LED connected to digital pin 13
> int ledPin2 = 12;
>
> void setup()
> {
>  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
>  pinMode(ledPin2, OUTPUT);
> }
>
> void loop()
> {
>  digitalWrite(ledPin, HIGH);   // sets the LED on
>  digitalWrite(ledPin2, HIGH);   // sets the LED on
>  delay(1500);                  // waits for a second
>  digitalWrite(ledPin, LOW);    // sets the LED off
>  delay(1500);                  // waits for a second
>  digitalWrite(ledPin2, LOW);    // sets the LED off
>  delay(1500);                  // waits for a second
> }
>
> One would expect this would turn on both LEDs, then wait a second,
> turn off LED1, wait, turn off LED2, wait, and then turn both on again.
> Instead it turns on LED2, waits, turns on LED1, Turns off LED2, turns
> off LED1, then repeats. In order to get the behavior I'm wanting, I
> had to do this
>
> int ledPin = 13;                 // LED connected to digital pin 13
> int ledPin2 = 12;
>
> void setup()
> {
>  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
>  pinMode(ledPin2, OUTPUT);
> }
>
> void loop()
> {
>  digitalWrite(ledPin, LOW);   // sets the LED on
>  digitalWrite(ledPin2, HIGH);   // sets the LED on
>  delay(1500);                  // waits for a second
>  digitalWrite(ledPin, HIGH);    // sets the LED off
>  delay(1500);                  // waits for a second
>  digitalWrite(ledPin2, LOW);    // sets the LED off
>  delay(1500);                  // waits for a second
> }
>
> Is there something wrong with my board? Have I declared something
> oddly? Why does 13 being set "high" turn the LED off, and being set
> low turn it on?
>
> - Aaron @jarvitron
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