possible to random choose a value from an array?

Forum 2005-2010 (read only) Software Troubleshooting
1

I am working on a firefly driver with my Arduino andI want to use the pwm outputs to drive the LEDs. I plan to light only one LED at a time. Since the PWM outputs are not all sequential, is it possible to use the Random() command to choose a value from an array?--each output pin would be a value in the array. What's the best way to go about this?

2

http://arduino.cc/en/Reference/Random

3

I looked at the Random() command pretty closely before asking. The problem I was having was that the PWM outputs are not all sequential, so you can't give it a limited range and expect it to always "land on" one of the preferred outputs. I did find another way, though. I used the random number generator with a range limitation. I then used IF statements to tell it that numbers 0-24 = output 1, 25-48 = output 2, etc. That seems to be about as clean as I can get it.

4

I looked at the Random() command pretty closely before asking

A lot of people don't - thanks!

If you put the PWM pin numbers into a constant array, thusly:
const byte pwmPins [] = {3, 5, 6, 9, 10, 11};
byte pwmPin;

And then use
"pwmPin = pwmPins [random (0, 5)];"

you'd get a random pin.

[EDIT] Oops - the docs say the max value is exclusive, so that should probably be
"pwmPin = pwmPins [random (0, 6)];"

5

That works perfectly, see my work here: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1245067981

Thanks for your help, AWOL. I just needed to get over the hump.

6

A couple of years ago over at avrfreaks, there were a few firefly projects, using many individual processors, and algorithms to mimic the synchronisation of real fireflies.