audio-reactive-led-strip/ws2812_i2s.cpp

// ws2812_lib.cpp
//
// main library file / contains class implementation
//
// Need to give credits to  Charles Lohr (https://github.com/cnlohr due 
// to his work on his software for driving ws2812 led-strips using 
// the i2s interface of the ESP8266.
//
// This inspired me to create an ESP8266 library for the Arduino IDE
// I've added temporal dithering & gamma-correction
// for a 'more natural' light intensity profile.
//
// No pin-definitions/mapings are required/possible as the library used the I2S 
// output-pin. This pin in it's turn is shared with GPIO3 & RXD0
//

#include <Arduino.h>
#include <stdint.h>
#include "ws2812_i2s.h"
#include "ws2812_defs.h"
#include "ws2812_gamma.h"

// include C-style header
extern "C"
{
#include "ws2812_dma.h"
};

// class constructor
WS2812::WS2812(void)
{
  // empty for now
}
  
// class de-constructor
WS2812::~WS2812(void)
{ 
  // empty for now
  // TODO : should implement switching of DMA
}

// Init led-string / memory buffers etc.
void WS2812::init(uint16_t _num_leds)
{
  uint8_t i;
  uint16_t j;

  num_leds = _num_leds;
  
  // clear zero buffer
  for(j=0; j<NUM_I2S_ZERO_WORDS; j++)
  {
    i2s_zeros_buffer[j] = 0;
  }

  // do memory allocation for i2s buffer(s)
  for(i=0; i<WS2812_DITHER_NUM; i++)
  {
    i2s_pixels_buffer[i] = new uint32_t[NUM_I2S_PIXEL_WORDS];

    // TODO : handle memory allocation error better
    if (i2s_pixels_buffer[i] == 0)
    {
      Serial.println("WS2812_I2S : ERROR ALLOCATING MEMORY");
      return;
    }
    
    for(j=0; j<NUM_I2S_PIXEL_WORDS; j++)
    {
      i2s_pixels_buffer[i][j] = 0;
    } 
  }

  // set-up DMA descriptors / 1 pair per dither-factor
  for(i=0; i<WS2812_DITHER_NUM; i++)
  {
    i2s_pixels_queue[i].owner     = 1;
    i2s_pixels_queue[i].eof       = 1;
    i2s_pixels_queue[i].sub_sof   = 0;
    i2s_pixels_queue[i].datalen   = NUM_I2S_PIXEL_BYTES;     // Size in bytes
    i2s_pixels_queue[i].blocksize = NUM_I2S_PIXEL_BYTES;     // Size in bytes
    i2s_pixels_queue[i].buf_ptr   = (uint32_t)i2s_pixels_buffer[i];
    i2s_pixels_queue[i].unused    = 0;
    i2s_pixels_queue[i].next_link_ptr = (uint32_t)&i2s_zeros_queue[i];  // always link to zeros-buffer

    i2s_zeros_queue[i].owner      = 1;
    i2s_zeros_queue[i].eof        = 1;
    i2s_zeros_queue[i].sub_sof    = 0;
    i2s_zeros_queue[i].datalen    = NUM_I2S_ZERO_BYTES;      // Size in bytes)
    i2s_zeros_queue[i].blocksize  = NUM_I2S_ZERO_BYTES;      // Size in bytes 
    i2s_zeros_queue[i].buf_ptr    = (uint32_t)i2s_zeros_buffer;  
    i2s_zeros_queue[i].unused     = 0;

    if (i == (WS2812_DITHER_NUM-1)) // last DMA descriptor in linked list ?
    {
      // yes : link to first DMA descriptor
      i2s_zeros_queue[i].next_link_ptr = (uint32_t)&i2s_pixels_queue[0];
    }
    else
    {
      // no : link to next DMA descriptor
      i2s_zeros_queue[i].next_link_ptr = (uint32_t)&i2s_pixels_queue[i+1];
    }
  }

  // call C based helper function
  // I did not really succeed in putting the code from the helper
  // funtion directly into this constructor...has something to do 
  // with  C vs. C++
  // the i2c_writeReg_Mask macro (+ others) failed.. see ws2812_defs.h
  // may be I solve this later

  // parameter = first entry in DMA descriptor list, i.e the descriptor list
  ws2812_dma(i2s_pixels_queue);

} 

// left this comment in tact....credit to Charles

// All functions below this line are Public Domain 2015 Charles Lohr.
// this code may be used by anyone in any way without restriction or limitation.

// Send out WS2812 bits with coded pulses, one nibble, then the other.
static const uint16_t bitpatterns[16] = 
{
  0b1000100010001000, 0b1000100010001110, 0b1000100011101000, 0b1000100011101110,
  0b1000111010001000, 0b1000111010001110, 0b1000111011101000, 0b1000111011101110,
  0b1110100010001000, 0b1110100010001110, 0b1110100011101000, 0b1110100011101110,
  0b1110111010001000, 0b1110111010001110, 0b1110111011101000, 0b1110111011101110,
};

// display the pixels
void WS2812::show(Pixel_t *pixels)
{
  uint8_t *buffer;
  uint8_t pixelbyte;
  uint8_t gammabyte;
  uint16_t i,b;
  uint16_t *i2s_ptr[WS2812_DITHER_NUM];

  buffer = (uint8_t *)pixels;

  // set-up pointers into the i2s-pixel-buffers  
  for(i=0; i<WS2812_DITHER_NUM; i++)
  {
    i2s_ptr[i] = (uint16_t *)i2s_pixels_buffer[i];
  }
    
  // for every pixel in the input-array
  // - get the pixel value (either R,G, or B)
  // - for every dithered buffer 
  //   get the gamma-corrected output value
  // - and transform into i2s nibble
  
  for(b=0; b<NUM_RGB_BYTES; b++)
  {
    pixelbyte = *buffer++;

    for(i=0; i<WS2812_DITHER_NUM; i++)
    {
      gammabyte = gamma_dither[i][pixelbyte];
      *(i2s_ptr[i]++) = bitpatterns[ (gammabyte & 0x0f) ];
      *(i2s_ptr[i]++) = bitpatterns[ (gammabyte>>4) & 0x0f ];
    }
  }

}

// end of file