File content as of revision 0:35d68d1652e1:

#include "mbed.h"
#include "wsDrive.h"

// time period between each movement
#define updatePeriodMS 25

// number of LEDs in chain
#define chainLen 144

// length of the fade off behind the bright spot.
// 1/8th of the chain length seems to look good (18 LEDs for a 144 chain)
#define glowTail (chainLen/8)

// background brightness left after the tail has passed.
// final brightness = peak/backgroundRatio
// set to be the same as the glow tail length for a smooth transition
#define backgroundRatio glowTail

// set the pulldown and then create the driver
DigitalIn dummy(P0_21,PullDown);
wsDrive ledDriver(P0_21,P0_22,P1_15);

// mbuino stnadard definitions
DigitalIn progMode(P0_3,PullDown); // fix the power wasted if we ever sleep.
BusOut LEDs(LED1, LED2, LED3, LED4, LED5, LED6, LED7); // control the LEDs

Timer updateRateTimer;

// pixel storage buffer
pixelInfo pixelData[chainLen];

void blankBuffer(pixelInfo *Ptr)
{
    memset( (void *)Ptr, 0, chainLen*sizeof(pixelInfo) );
}

void setPixel (pixelInfo *pixel, pixelInfo *colour, float level)
{

    pixel->R = (unsigned char) (colour->R * level);
    pixel->G = (unsigned char) (colour->G * level);
    pixel->B = (unsigned char) (colour->B * level);
}


void setTrail (pixelInfo *colour, int peakPoint, bool increasing, int len)
{
    int pixelToUpdate = peakPoint;
    for (int pixel = 0; pixel <= len; pixel++) {
        if (pixel == len) {
            setPixel((pixelData+pixelToUpdate), colour, 1.0/backgroundRatio);
            break;
        }
        setPixel((pixelData+pixelToUpdate), colour, 1.0 - (float)pixel/(float)len);
        increasing ? pixelToUpdate-- : pixelToUpdate++;
        if (pixelToUpdate == chainLen) {
            increasing = false;
            pixelToUpdate = peakPoint - 1;
            pixel = pixel*2;
        }
        if (pixelToUpdate == -1) {
            increasing = true;
            pixelToUpdate = peakPoint + 1;
            pixel = pixel*2;
        }
    }
}


void setColour(pixelInfo *colour)
{
    static int cycleNumber = 0;

    const int maxCycle = 40;
    if (cycleNumber > maxCycle)
        cycleNumber = 0;

    switch (cycleNumber) {
        case maxCycle:
            cycleNumber = 0;
        case 0:
            colour->R = 0x80;
            colour->G = 0x00;
            colour->B = 0x00;
            break;
        case 10:
            colour->R = 0x00;
            colour->G = 0x70;
            colour->B = 0x00;
            break;
        case 20:
            colour->R = 0x00;
            colour->G = 0x00;
            colour->B = 0x80;
            break;
        case 30:
            colour->R = 0x50;
            colour->G = 0x40;
            colour->B = 0x50;
            break;
        default:
            break;
    }
    cycleNumber++;
}


int main ()
{
    LEDs = 0;
    // intialise variables
    int peakPoint = 0;
    bool increasing = true;

    pixelInfo colour;
    setColour(&colour);

    blankBuffer(pixelData);

    // give the LED driver the buffer to use.
    ledDriver.setData(pixelData, chainLen);

    LEDs = 1;

    setTrail (&colour, peakPoint, increasing, glowTail); // set the LED data

    updateRateTimer.start();
    while (true) {
        ledDriver.sendData(); // send the LED data
        LEDs = LEDs+1;

        increasing ? peakPoint++ : peakPoint--; 
        if (peakPoint == chainLen) {
            increasing = false;
            peakPoint = chainLen-2;
        }
        if (peakPoint == -1) {
            setColour(&colour);
            increasing = true;
            peakPoint = 1;
        }
        
        // update to the next trail ready for the next update.
        setTrail (&colour, peakPoint, increasing, glowTail); // set the LED data

        // wait for the next update time.
        while (updateRateTimer.read_ms() < updatePeriodMS) {
        }
        updateRateTimer.reset();
    }

}