ws2812 is an RGB LED which has individually included LED controller.

Each LEDs can be controlled one by one using serial signal.

I made a signal using an OC module and DMA and output an Audio port to the LED strip.

#include <sys.h>
#include <file.h>
#include <p270256b.h>

#define LEDs 60
#define OVERSAMPLEx 4
#define VLEDs (LEDs*OVERSAMPLEx)

typedef struct{
  unsigned char r;
  unsigned char g;
  unsigned char b;
} led_t;


// ====================
// ======led task======
// ====================

// ===DMA setting===
// *addr ==> OC4RS
// trig TMR4 irq
// 1byte per event
// destination size is 1byte.
// src size is `size`

// DMA channel 1 and 2 for SD, channel 3 for keyboard, so we use channel 0 to audio.(No more DMA channel;)

void initdma(char *addr,unsigned size){
  DMACON[SET]    = 0x8000;
  DCH0CON[ORIG]  = 0x02;
  DCH0ECON[ORIG] = (14<<8)|(1<<4);
  DCH0SSA[ORIG]  = ((unsigned)addr) & 0x1FFFFFFF;
  DCH0DSA[ORIG]  = ((unsigned)OC4RS) & 0x1FFFFFFF;
  DCH0SSIZ[ORIG] = size;
  DCH0DSIZ[ORIG] = 1;
  DCH0CSIZ[ORIG] = 1;
  DCH0INT[CLR]   = 0x00FF00FF;
//  DCH0CON[SET]   = 0x80;
}

#define CLRFLG DCH0INT[CLR] = 0x00FF00FF
#define ISHALFDONE DCH0INT[ORIG] & 0x40
#define ISALLDONE  DCH0INT[ORIG] & 0x80


// ===PWM settings===
// use timer3
// use OC4
// pwm max duty = 0xFF (8bit)
// output PB13

void setuppwm(void){
  RPB13R[ORIG]= 5;
  PR3[ORIG]   = 60;
  TMR3[ORIG]  = 0;
  T3CON[SET]  = 0x8000;
  OC4CON[ORIG]= 0x000e;
  OC4CON[SET] = 0x8000;
}

unsigned char ledtransbuff[LEDs*24+60];
void initled(void){
  setuppwm();
  initdma(ledtransbuff,sizeof(ledtransbuff));
}

void calcdata(led_t *leds){
  int i,j;
  int t;
  for(i=0;i<LEDs;i++){
    t = 0;
    for(j=0;j<OVERSAMPLEx;j++)
      t += leds[i*OVERSAMPLEx+j].g;
    t /= OVERSAMPLEx;
    for(j=0;j<8;j++){
      ledtransbuff
      [i*24+j]=(t&(1<<(7-j)))?40:15;
    }
    t=0;
    for(j=0;j<OVERSAMPLEx;j++)
      t += leds[i*OVERSAMPLEx+j].r;
    t /= OVERSAMPLEx;
    for(j=0;j<8;j++){
      ledtransbuff
      [i*24+j+8]=(t&(1<<(7-j)))?40:15;
    }
    t=0;
    for(j=0;j<OVERSAMPLEx;j++)
      t += leds[i*OVERSAMPLEx+j].b;
    t /= OVERSAMPLEx;
    for(j=0;j<8;j++){
      ledtransbuff
      [i*24+j+16]=(t&(1<<(7-j)))?40:15;
    }
  }
}

void resend(led_t *leds){
  calcdata(leds);
  while(!(ISALLDONE));
  DCH0CON[SET]   = 0x80;
  CLRFLG;
}

void send(led_t *leds){
  calcdata(leds);
  DCH0CON[SET]   = 0x80;
  CLRFLG;
}

void pattern1(int p,int l,led_t c,led_t *led){
 int k;
 l*=OVERSAMPLEx;
 c.r /= l;
 c.g /= l;
 c.b /= l;
 for(k=0;k<l;k++){
  led[(p+VLEDs+k)%VLEDs].r += k*c.r;
  led[(p+VLEDs+k)%VLEDs].g += k*c.g;
  led[(p+VLEDs+k)%VLEDs].b += k*c.b;
  led[(p+VLEDs+l+k)%VLEDs].r+=(l-k)*c.r;
  led[(p+VLEDs+l+k)%VLEDs].g+=(l-k)*c.g;
  led[(p+VLEDs+l+k)%VLEDs].b+=(l-k)*c.b;
 }
}

int main(int argc,char **argv){  
  int i,k;
  led_t led[LEDs*OVERSAMPLEx]={{0,0,0}};

  initled();
  send(led);
  while(ps2keystatus[0xD]);
  led_t col[]={{100,100,100},{200,100,0},{0,200,100}};
    for(i=0;i<VLEDs/3;i++){
      led[i].r = 150;
      led[i].b = 150;
      led[i].g = 150;
    }
    resend(led);
    wait60thsec(30*8);
    for(i=0;i<VLEDs/3;i++){
      led[i].r = 0;
      led[i].b = 0;
      led[i].g = 0;
    }
    resend(led);

return 0;
  while(1){
   for(k=0;k<VLEDs;k++){
    for(i=0;i<VLEDs;i++){
      led[i].r = 0;
      led[i].b = 0;
      led[i].g = 0;
    }
    for(i=0;i<sizeof(col)/sizeof(col[0]);i++){
      pattern1(k+i*90,4,col[i],led);
    }
    resend(led);
    if(ps2keystatus[0xD])break;
   }
    resend(led);
    if(ps2keystatus[0xD])break;
  }

// Return to quit.
  wait60thsec(1);

  return 0;
}