How can I randomly select an Arduino pin output?

Question

I have a series of eight LEDs that I'm trying to fade in and out randomly, starting from ON. Here's where I am so far.

#define LED1 2
#define LED2 3
#define LED3 4
#define LED4 5
#define LED5 6
#define LED6 7
#define LED7 8
#define LED8 9

void setup() {
pinMode(LED1,output);
pinMode(LED2,output);
pinMode(LED3,output);
pinMode(LED4,output);
pinMode(LED5,output);
pinMode(LED6,output);
pinMode(LED7,output);
pinMode(LED8,output);
}

    void cycleLED() {
        timeOn = random(600,1800);
        timeOff = random(600,1800);
        for (fadeOut = 255; fadeOut > 0; fadeOut--) { 
            analogWrite(LED, fadeout);
            delay(timeOff); 
        }

        for (fadeIn = 0;fadeIn < 255; fadeIn++) { 
            analogWrite(LED,fadeIn);      
            delay(timeOn); 
        }
    }

Here's where I'm stuck. I want to do something similar to the following pseudocode.

activeLED = random(2,10);             // choose a random LED pin
LEDtoCycle = pinNumber-activeLED;     // set the active LED to the random LED pin 
cycleLED(pinNumber-activeLED);        // run cycleLED on the active LED

My intention is to select an LED at random, then to run cycleLED on that LED, repeating indefinitely. By choosing random However, I'm having a hard time wrapping my head around a good way to do this. How do I pass the pin variable to cycleLED()? Or should I repeatedly #define a single, random LED? Or should I just hardcode eight separate instances of cycleLED1(), cycleLED2(), cycleLED3(), and so forth.

Tips or suggestions?

"How do I pass the pin variable to cycleLED()?" - euh, using an argument to that function, perhaps? — user529758
– user529758, Commented Dec 31, 2012 at 14:37

Chris Desjardins · Accepted Answer · 2012-12-31 14:39:13Z

2

You can make the cycleLED function take a parameter as follows:

void cycleLED(int led)

Then just use the led variable in your analogWrite calls in lieu of the mysterious LED thing you currently have.

answered Dec 31, 2012 at 14:39

Chris Desjardins

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