nodemcu-firmware/app/modules/ws2812.c

#include "lualib.h"
#include "lauxlib.h"
#include "platform.h"
#include "auxmods.h"
#include "lrotable.h"
/**
 * All this code is mostly from http://www.esp8266.com/viewtopic.php?f=21&t=1143&sid=a620a377672cfe9f666d672398415fcb
 * from user Markus Gritsch.
 * I just put this code into its own module and pushed into a forked repo,
 * to easily create a pull request. Thanks to Markus Gritsch for the code.
 */

// ----------------------------------------------------------------------------
// -- This WS2812 code must be compiled with -O2 to get the timing right.  Read this:
// -- http://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
// -- The ICACHE_FLASH_ATTR is there to trick the compiler and get the very first pulse width correct.
static void ICACHE_FLASH_ATTR send_ws_0(uint8_t gpio) {
  uint8_t i;
  i = 4; while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, 1 << gpio);
  i = 9; while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, 1 << gpio);
}

static void ICACHE_FLASH_ATTR send_ws_1(uint8_t gpio) {
  uint8_t i;
  i = 8; while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, 1 << gpio);
  i = 6; while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, 1 << gpio);
}

// Lua: ws2812.write(pin, "string")
// Byte triples in the string are interpreted as R G B values and sent to the hardware as G R B.
// ws2812.write(4, string.char(255, 0, 0)) uses GPIO2 and sets the first LED red.
// ws2812.write(3, string.char(0, 0, 255):rep(10)) uses GPIO0 and sets ten LEDs blue.
// ws2812.write(4, string.char(0, 255, 0, 255, 255, 255)) first LED green, second LED white.
static int ICACHE_FLASH_ATTR ws2812_writergb(lua_State* L)
{
  const uint8_t pin = luaL_checkinteger(L, 1);
  size_t length;
  char *buffer = (char *)luaL_checklstring(L, 2, &length); // Cast away the constness.

  // Initialize the output pin:
  platform_gpio_mode(pin, PLATFORM_GPIO_OUTPUT, PLATFORM_GPIO_FLOAT);
  platform_gpio_write(pin, 0);

  // Ignore incomplete Byte triples at the end of buffer:
  length -= length % 3;

  // Rearrange R G B values to G R B order needed by WS2812 LEDs:
  size_t i;
  for (i = 0; i < length; i += 3) {
    const char r = buffer[i];
    const char g = buffer[i + 1];
    buffer[i] = g;
    buffer[i + 1] = r;
  }

  // Do not remove these:
  os_delay_us(1);
  os_delay_us(1);

  // Send the buffer:
  os_intr_lock();
  const char * const end = buffer + length;
  while (buffer != end) {
    uint8_t mask = 0x80;
    while (mask) {
      (*buffer & mask) ? send_ws_1(pin_num[pin]) : send_ws_0(pin_num[pin]);
      mask >>= 1;
    }
    ++buffer;
  }
  os_intr_unlock();

  return 0;
}

#define MIN_OPT_LEVEL 2
#include "lrodefs.h"
const LUA_REG_TYPE ws2812_map[] =
{
  { LSTRKEY( "writergb" ), LFUNCVAL( ws2812_writergb )},
  { LNILKEY, LNILVAL}
};

LUALIB_API int luaopen_ws2812(lua_State *L) {
  // TODO: Make sure that the GPIO system is initialized
  LREGISTER(L, "ws2812", ws2812_map);
  return 1;
}