light_ws2812.c

/*
* light weight WS2812 lib V2.0b
*
* Controls WS2811/WS2812/WS2812B RGB-LEDs
* Author: Tim (cpldcpu@gmail.com)
*
* Jan 18th, 2014  v2.0b Initial Version
*
* License: GNU GPL v2 (see License.txt)
*/

#include "light_ws2812.h"
#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>
 
void inline ws2812_setleds(struct cRGB *ledarray, uint16_t leds)
{
   ws2812_setleds_pin(ledarray,leds, _BV(ws2812_pin));
}

void inline ws2812_setleds_pin(struct cRGB *ledarray, uint16_t leds, uint8_t pinmask)
{
  ws2812_DDRREG |= _BV(ws2812_pin); // Enable DDR
  ws2812_sendarray_mask((uint8_t*)ledarray,leds+leds+leds,pinmask);
  _delay_us(50);
}

void ws2812_sendarray(uint8_t *data,uint16_t datlen)
{
  ws2812_sendarray_mask(data,datlen,_BV(ws2812_pin));
}

/*
  This routine writes an array of bytes with RGB values to the Dataout pin
  using the fast 800kHz clockless WS2811/2812 protocol.
*/

// Timing in ns
#define w_zeropulse   350
#define w_onepulse    900
#define w_totalperiod 1250

// Fixed cycles used by the inner loop
#define w_fixedlow    2
#define w_fixedhigh   4
#define w_fixedtotal  8   

// Insert NOPs to match the timing, if possible
#define w_zerocycles    (((F_CPU/1000)*w_zeropulse          )/1000000)
#define w_onecycles     (((F_CPU/1000)*w_onepulse    +500000)/1000000)
#define w_totalcycles   (((F_CPU/1000)*w_totalperiod +500000)/1000000)

// w1 - nops between rising edge and falling edge - low
#define w1 (w_zerocycles-w_fixedlow)
// w2   nops between fe low and fe high
#define w2 (w_onecycles-w_fixedhigh-w1)
// w3   nops to complete loop
#define w3 (w_totalcycles-w_fixedtotal-w1-w2)

#if w1>0
  #define w1_nops w1
#else
  #define w1_nops  0
#endif

// The only critical timing parameter is the minimum pulse length of the "0"
// Warn or throw error if this timing can not be met with current F_CPU settings.
#define w_lowtime ((w1_nops+w_fixedlow)*1000000)/(F_CPU/1000)
#if w_lowtime>550
   #error "Light_ws2812: Sorry, the clock speed is too low. Did you set F_CPU correctly?"
#elif w_lowtime>450
   #warning "Light_ws2812: The timing is critical and may only work on WS2812B, not on WS2812(S)."
   #warning "Please consider a higher clockspeed, if possible"
#endif   

#if w2>0
#define w2_nops w2
#else
#define w2_nops  0
#endif

#if w3>0
#define w3_nops w3
#else
#define w3_nops  0
#endif

#define w_nop1  "nop      \n\t"
#define w_nop2  "rjmp .+0 \n\t"
#define w_nop4  w_nop2 w_nop2
#define w_nop8  w_nop4 w_nop4
#define w_nop16 w_nop8 w_nop8

void inline ws2812_sendarray_mask(uint8_t *data,uint16_t datlen,uint8_t maskhi)
{
  uint8_t curbyte,ctr,masklo;
  uint8_t sreg_prev;
  
  masklo	=~maskhi&ws2812_PORTREG;
  maskhi |=        ws2812_PORTREG;
  sreg_prev=SREG;
  cli();  

  while (datlen--) {
    curbyte=*data++;
    
    asm volatile(
    "       ldi   %0,8  \n\t"
    "loop%=:            \n\t"
    "       out   %2,%3 \n\t"    //  '1' [01] '0' [01] - re
#if (w1_nops&1)
w_nop1
#endif
#if (w1_nops&2)
w_nop2
#endif
#if (w1_nops&4)
w_nop4
#endif
#if (w1_nops&8)
w_nop8
#endif
#if (w1_nops&16)
w_nop16
#endif
    "       sbrs  %1,7  \n\t"    //  '1' [03] '0' [02]
    "       out   %2,%4 \n\t"    //  '1' [--] '0' [03] - fe-low
    "       lsl   %1    \n\t"    //  '1' [04] '0' [04]
#if (w2_nops&1)
  w_nop1
#endif
#if (w2_nops&2)
  w_nop2
#endif
#if (w2_nops&4)
  w_nop4
#endif
#if (w2_nops&8)
  w_nop8
#endif
#if (w2_nops&16)
  w_nop16 
#endif
    "       out   %2,%4 \n\t"    //  '1' [+1] '0' [+1] - fe-high
#if (w3_nops&1)
w_nop1
#endif
#if (w3_nops&2)
w_nop2
#endif
#if (w3_nops&4)
w_nop4
#endif
#if (w3_nops&8)
w_nop8
#endif
#if (w3_nops&16)
w_nop16
#endif

    "       dec   %0    \n\t"    //  '1' [+2] '0' [+2]
    "       brne  loop%=\n\t"    //  '1' [+3] '0' [+4]
    :	"=&d" (ctr)
    :	"r" (curbyte), "I" (_SFR_IO_ADDR(ws2812_PORTREG)), "r" (maskhi), "r" (masklo)
    );
  }
  
  SREG=sreg_prev;
}