Proof of concept for running multiple sequences on Neopixel LED strips. By no means optimized or clever...

kind of asynchronous, but not really

//testing RTOS for multiple neopixel strips
//ChibiOS for Arduino sourced from: http://code.google.com/p/rtoslibs/

#include <ChibiOS_AVR.h>
#include <Adafruit_NeoPixel.h>
Adafruit_NeoPixel strip1 = Adafruit_NeoPixel(3, 8, NEO_GRB + NEO_KHZ800);
Adafruit_NeoPixel strip2 = Adafruit_NeoPixel(3, 9, NEO_GRB + NEO_KHZ800);

uint8_t wait = 100;
uint8_t r = 255;
uint8_t g = 0;
uint8_t b = 255;
uint32_t steps = 20;
uint32_t steps2 = 40;
volatile uint32_t i1,i2,j1,j2 = 0;

//------------------------------------------------------------------------------
// thread 1 - high priority for neopixel pulse
// 100 byte stack beyond task switch and interrupt needs
static WORKING_AREA(waThread1, 100);

static msg_t Thread1(void *arg) {
  while(true){
    byte _r, _g, _b;
    for(i1 = 1; i1 < steps; i1++)
    {
      //set color level color channel / steps
      _r = (byte)r/i1;
      _g = (byte)g/i1;
      _b = (byte)b/i1;

      for(j1 = 0; j1 < strip1.numPixels(); j1++)
      {
        //set led color
        strip1.setPixelColor(j1, _r, _g, _b);
      }
      strip1.show();
      // Serial.println("1 in" + i1);
      chThdSleepMilliseconds(wait);
    }

    for(i1 = steps; i1 > 1; i1--)
    {
      //set color level color channel / steps
      _r = (byte)r/i1;
      _g = (byte)g/i1;
      _b = (byte)b/i1;

      for(j1 = 0; j1 < strip1.numPixels(); j1++)
      {
        //set led color
        strip1.setPixelColor(j1, _r, _g, _b);
      }
      strip1.show();
      //Serial.println("1 out" + i1);
      chThdSleepMilliseconds(wait);
    }
  }
}

//------------------------------------------------------------------------------
// thread 2 - high priority for neopixel pulse
// 100 byte stack beyond task switch and interrupt needs
static WORKING_AREA(waThread2, 100);

static msg_t Thread2(void *arg) {
  while(true){
    byte _r, _g, _b;
    for(i2 = 1; i2 < steps2; i2++)
    {
      //set color level color channel / steps
      _r = (byte)r/i2;
      _g = (byte)g/i2;
      _b = (byte)b/i2;

      for( j2 = 0; j2 < strip2.numPixels(); j2++)
      {
        //set led color
        strip2.setPixelColor(j2, _r, _g, _b);
      }
      strip2.show();
      chThdSleepMilliseconds(wait);
    }

    for( i2 = steps2; i2 > 1; i2--)
    {
      //set color level color channel / steps
      _r = (byte)r/i2;
      _g = (byte)g/i2;
      _b = (byte)b/i2;

      for( j2 = 0; j2 < strip2.numPixels(); j2++)
      {
        //set led color
        strip2.setPixelColor(j2, _r, _g, _b);
      }
      strip2.show();
      chThdSleepMilliseconds(wait);
    }
  }
}

void setup() {
  strip1.begin();
  strip2.begin();
  strip1.show(); // Initialize all pixels to 'off'
  strip2.show(); // Initialize all pixels to 'off'
  Serial.begin(9600);
  while (!Serial) {
  }
  chBegin(mainThread);
  // chBegin never returns, main thread continues with mainThread()
  while(1) {
  }
}

//------------------------------------------------------------------------------
// main thread runs at NORMALPRIO
void mainThread() {

  // start strip 1 pulse
  chThdCreateStatic(waThread1, sizeof(waThread1),NORMALPRIO + 1, Thread1, NULL);

  // start strip 2 pulse
  chThdCreateStatic(waThread2, sizeof(waThread2),NORMALPRIO + 1, Thread2, NULL);

  // let other things happen
  while (1) {
    chThdSleepMilliseconds(10);
  }
}
//------------------------------------------------------------------------------
void loop() {
  // not used
}