shuffle_function.txt

For Bill from this post:
https://plus.google.com/u/0/109149766109138486006/posts/J9Xnqthpgsh
//---------------------------------------------------------------


Somewhere at the top of the program:

#define NUM_LEDS 32  //length of one strip
#define DBL_LEDS NUM_LEDS*2  //double the length of one strip
CRGB ledsA[NUM_LEDS];  //strip A (gets displayed)
CRGB ledsB[NUM_LEDS];  //strip B (gets displayed)
CRGB temp[DBL_LEDS];  //temporary working array (not displayed)



//---------------------------------------------------------------
In the setup section, something like this for the two strips ledsA and ledsB:

FastLED.addLeds<APA102, DATA_PIN, CLOCK_PIN, RGB>(ledsA, NUM_LEDS);
FastLED.addLeds<APA102, DATA_PIN2, CLOCK_PIN2, RGB>(ledsB, NUM_LEDS);



//---------------------------------------------------------------
In the main loop when assigning color, opperate on the "temp"
array and use DBL_LEDS as the number of pixels.  For example:

fill_rainbow( temp, DBL_LEDS, millis()/5);



Call the shuffle function right before running show:

ShufflePixels();
FastLED.show();



//---------------------------------------------------------------
And a shuffle function:

void ShufflePixels()
// Function to shuffle pixels before displaying.
//
// Have "temp" array data like this:
// 0,1,2,3,4,5 ... DBL_LEDS
//
// Want it shuffled and distributed to two strips like this:
// 0,2,4,6...
// 1,3,5,7...

{
  uint16_t c = 1;
  for (uint8_t i=0; i<DBL_LEDS; i++) {
    if ((i & 0x01) == 0) {  //number is even
      ledsA[c/2] = temp[i]; 
    } else {                //number is odd
      ledsB[(c/2)-1] = temp[i];
    }
    c++;
  }
}//end ShufflePixels