battletank/arduino/libraries/Adafruit_Circuit_Playground/utility/Adafruit_CPlay_NeoPixel.cpp

/*-------------------------------------------------------------------------
  Arduino library to control a wide variety of WS2811- and WS2812-based RGB
  LED devices such as Adafruit FLORA RGB Smart Pixels and NeoPixel strips.
  Currently handles 400 and 800 KHz bitstreams on 8, 12 and 16 MHz ATmega
  MCUs, with LEDs wired for various color orders.  8 MHz MCUs provide
  output on PORTB and PORTD, while 16 MHz chips can handle most output pins
  (possible exception with upper PORT registers on the Arduino Mega).

  Written by Phil Burgess / Paint Your Dragon for Adafruit Industries,
  contributions by PJRC, Michael Miller and other members of the open
  source community.

  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing products
  from Adafruit!

  -------------------------------------------------------------------------
  This file is part of the Adafruit NeoPixel library.

  NeoPixel is free software: you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as
  published by the Free Software Foundation, either version 3 of
  the License, or (at your option) any later version.

  NeoPixel is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with NeoPixel.  If not, see
  <http://www.gnu.org/licenses/>.
  -------------------------------------------------------------------------*/

#include "Adafruit_CPlay_NeoPixel.h"

/**************************************************************************/
/*! 
    @brief  Constructor when length, pin and type are known at compile-time
    @param n number of pixels
    @param p pin the pixels are attached to
    @param t the type of neopixel. can be NEO_KHZ800 or NEO_KHZ400
*/
/**************************************************************************/
Adafruit_CPlay_NeoPixel::Adafruit_CPlay_NeoPixel(uint16_t n, uint8_t p, neoPixelType t) :
  begun(false), brightness(0), pixels(NULL), endTime(0)
{
  updateType(t);
  updateLength(n);
  setPin(p);
}

// via Michael Vogt/neophob: empty constructor is used when strand length
// isn't known at compile-time; situations where program config might be
// read from internal flash memory or an SD card, or arrive via serial
// command.  If using this constructor, MUST follow up with updateType(),
// updateLength(), etc. to establish the strand type, length and pin number!

/**************************************************************************/
/*! 
    @brief  via Michael Vogt/neophob: empty constructor is used when strand length
      isn't known at compile-time; situations where program config might be
      read from internal flash memory or an SD card, or arrive via serial
      command.  If using this constructor, MUST follow up with updateType(),
      updateLength(), etc. to establish the strand type, length and pin number!
*/
/**************************************************************************/
Adafruit_CPlay_NeoPixel::Adafruit_CPlay_NeoPixel() :
  is800KHz(true),
  begun(false), numLEDs(0), numBytes(0), pin(-1), brightness(0), pixels(NULL),
  rOffset(1), gOffset(0), bOffset(2), wOffset(1), endTime(0)
{
}

Adafruit_CPlay_NeoPixel::~Adafruit_CPlay_NeoPixel() {
  if(pixels)   free(pixels);
  if(pin >= 0) pinMode(pin, INPUT);
  pixels = NULL;
}

/**************************************************************************/
/*! 
    @brief  initialize necessary hardware to drive the pixels.
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::begin(void) {
  if(pin >= 0) {
    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
  }
  begun = true;
}

/**************************************************************************/
/*! 
    @brief  Set the number of pixels in the strip
    @param n the number of pixels in the strip
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::updateLength(uint16_t n) {
  if(pixels) free(pixels); // Free existing data (if any)

  // Allocate new data -- note: ALL PIXELS ARE CLEARED
  numBytes = n * ((wOffset == rOffset) ? 3 : 4);
  if((pixels = (uint8_t *)malloc(numBytes))) {
    memset(pixels, 0, numBytes);
    numLEDs = n;
  } else {
    numLEDs = numBytes = 0;
  }
}

/**************************************************************************/
/*! 
    @brief  set the type of neopixel we are using
    @param t the type of neopixel. Can be NEO_KHZ800 or NEO_KHZ400
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::updateType(neoPixelType t) {
  boolean oldThreeBytesPerPixel = (wOffset == rOffset); // false if RGBW

  wOffset = (t >> 6) & 0b11; // See notes in header file
  rOffset = (t >> 4) & 0b11; // regarding R/G/B/W offsets
  gOffset = (t >> 2) & 0b11;
  bOffset =  t       & 0b11;
  is800KHz = (t < 256);      // 400 KHz flag is 1<<8

  // If bytes-per-pixel has changed (and pixel data was previously
  // allocated), re-allocate to new size.  Will clear any data.
  if(pixels) {
    boolean newThreeBytesPerPixel = (wOffset == rOffset);
    if(newThreeBytesPerPixel != oldThreeBytesPerPixel) updateLength(numLEDs);
  }
}

/**************************************************************************/
/*! 
    @brief  Write data to the neopixels
    @note this disables interrupts on the chip until the write is complete.
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::show(void) {

  if(!pixels) return;

  // Data latch = 50+ microsecond pause in the output stream.  Rather than
  // put a delay at the end of the function, the ending time is noted and
  // the function will simply hold off (if needed) on issuing the
  // subsequent round of data until the latch time has elapsed.  This
  // allows the mainline code to start generating the next frame of data
  // rather than stalling for the latch.
  while(!canShow());
  // endTime is a private member (rather than global var) so that mutliple
  // instances on different pins can be quickly issued in succession (each
  // instance doesn't delay the next).

  // In order to make this code runtime-configurable to work with any pin,
  // SBI/CBI instructions are eschewed in favor of full PORT writes via the
  // OUT or ST instructions.  It relies on two facts: that peripheral
  // functions (such as PWM) take precedence on output pins, so our PORT-
  // wide writes won't interfere, and that interrupts are globally disabled
  // while data is being issued to the LEDs, so no other code will be
  // accessing the PORT.  The code takes an initial 'snapshot' of the PORT
  // state, computes 'pin high' and 'pin low' values, and writes these back
  // to the PORT register as needed.

  noInterrupts(); // Need 100% focus on instruction timing

#ifdef __AVR__
// AVR MCUs -- ATmega & ATtiny (no XMEGA) ---------------------------------

  volatile uint16_t
    i   = numBytes; // Loop counter
  volatile uint8_t
   *ptr = pixels,   // Pointer to next byte
    b   = *ptr++,   // Current byte value
    hi,             // PORT w/output bit set high
    lo;             // PORT w/output bit set low

  // Hand-tuned assembly code issues data to the LED drivers at a specific
  // rate.  There's separate code for different CPU speeds (8, 12, 16 MHz)
  // for both the WS2811 (400 KHz) and WS2812 (800 KHz) drivers.  The
  // datastream timing for the LED drivers allows a little wiggle room each
  // way (listed in the datasheets), so the conditions for compiling each
  // case are set up for a range of frequencies rather than just the exact
  // 8, 12 or 16 MHz values, permitting use with some close-but-not-spot-on
  // devices (e.g. 16.5 MHz DigiSpark).  The ranges were arrived at based
  // on the datasheet figures and have not been extensively tested outside
  // the canonical 8/12/16 MHz speeds; there's no guarantee these will work
  // close to the extremes (or possibly they could be pushed further).
  // Keep in mind only one CPU speed case actually gets compiled; the
  // resulting program isn't as massive as it might look from source here.

// 8 MHz(ish) AVR ---------------------------------------------------------
#if (F_CPU >= 7400000UL) && (F_CPU <= 9500000UL)

  if(is800KHz) {

    volatile uint8_t n1, n2 = 0;  // First, next bits out

    // Squeezing an 800 KHz stream out of an 8 MHz chip requires code
    // specific to each PORT register.  At present this is only written
    // to work with pins on PORTD or PORTB, the most likely use case --
    // this covers all the pins on the Adafruit Flora and the bulk of
    // digital pins on the Arduino Pro 8 MHz (keep in mind, this code
    // doesn't even get compiled for 16 MHz boards like the Uno, Mega,
    // Leonardo, etc., so don't bother extending this out of hand).
    // Additional PORTs could be added if you really need them, just
    // duplicate the else and loop and change the PORT.  Each add'l
    // PORT will require about 150(ish) bytes of program space.

    // 10 instruction clocks per bit: HHxxxxxLLL
    // OUT instructions:              ^ ^    ^   (T=0,2,7)


      // Same as above, just switched to PORTB and stripped of comments.
      hi = PORTB |  pinMask;
      lo = PORTB & ~pinMask;
      n1 = lo;
      if(b & 0x80) n1 = hi;

      asm volatile(
       "cp_headB:"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n2]   , %[lo]"    "\n\t"
        "out  %[port] , %[n1]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 6"        "\n\t"
         "mov %[n2]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n1]   , %[lo]"    "\n\t"
        "out  %[port] , %[n2]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 5"        "\n\t"
         "mov %[n1]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n2]   , %[lo]"    "\n\t"
        "out  %[port] , %[n1]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 4"        "\n\t"
         "mov %[n2]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n1]   , %[lo]"    "\n\t"
        "out  %[port] , %[n2]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 3"        "\n\t"
         "mov %[n1]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n2]   , %[lo]"    "\n\t"
        "out  %[port] , %[n1]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 2"        "\n\t"
         "mov %[n2]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n1]   , %[lo]"    "\n\t"
        "out  %[port] , %[n2]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 1"        "\n\t"
         "mov %[n1]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n2]   , %[lo]"    "\n\t"
        "out  %[port] , %[n1]"    "\n\t"
        "rjmp .+0"                "\n\t"
        "sbrc %[byte] , 0"        "\n\t"
         "mov %[n2]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "sbiw %[count], 1"        "\n\t"
        "out  %[port] , %[hi]"    "\n\t"
        "mov  %[n1]   , %[lo]"    "\n\t"
        "out  %[port] , %[n2]"    "\n\t"
        "ld   %[byte] , %a[ptr]+" "\n\t"
        "sbrc %[byte] , 7"        "\n\t"
         "mov %[n1]   , %[hi]"    "\n\t"
        "out  %[port] , %[lo]"    "\n\t"
        "brne cp_headB"           "\n"
      : [byte] "+r" (b), [n1] "+r" (n1), [n2] "+r" (n2), [count] "+w" (i)
      : [port] "I" (_SFR_IO_ADDR(PORTB)), [ptr] "e" (ptr), [hi] "r" (hi),
        [lo] "r" (lo));

  } else { // end 800 KHz, do 400 KHz

    // Timing is more relaxed; unrolling the inner loop for each bit is
    // not necessary.  Still using the peculiar RJMPs as 2X NOPs, not out
    // of need but just to trim the code size down a little.
    // This 400-KHz-datastream-on-8-MHz-CPU code is not quite identical
    // to the 800-on-16 code later -- the hi/lo timing between WS2811 and
    // WS2812 is not simply a 2:1 scale!

    // 20 inst. clocks per bit: HHHHxxxxxxLLLLLLLLLL
    // ST instructions:         ^   ^     ^          (T=0,4,10)

    volatile uint8_t next, bit;

    hi   = *port |  pinMask;
    lo   = *port & ~pinMask;
    next = lo;
    bit  = 8;

    asm volatile(
     "cp_head20:"               "\n\t" // Clk  Pseudocode    (T =  0)
      "st   %a[port], %[hi]"    "\n\t" // 2    PORT = hi     (T =  2)
      "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 128)
      "mov  %[next], %[hi]"     "\n\t" // 0-1   next = hi    (T =  4)
      "st   %a[port], %[next]"  "\n\t" // 2    PORT = next   (T =  6)
      "mov  %[next] , %[lo]"    "\n\t" // 1    next = lo     (T =  7)
      "dec  %[bit]"             "\n\t" // 1    bit--         (T =  8)
      "breq cp_nextbyte20"      "\n\t" // 1-2  if(bit == 0)
      "rol  %[byte]"            "\n\t" // 1    b <<= 1       (T = 10)
      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 12)
      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 14)
      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 16)
      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 18)
      "rjmp cp_head20"          "\n\t" // 2    -> head20 (next bit out)
       "cp_nextbyte20:"         "\n\t" //                    (T = 10)
      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 12)
      "nop"                     "\n\t" // 1    nop           (T = 13)
      "ldi  %[bit]  , 8"        "\n\t" // 1    bit = 8       (T = 14)
      "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++    (T = 16)
      "sbiw %[count], 1"        "\n\t" // 2    i--           (T = 18)
      "brne cp_head20"          "\n"   // 2    if(i != 0) -> (next byte)
      : [port]  "+e" (port),
        [byte]  "+r" (b),
        [bit]   "+r" (bit),
        [next]  "+r" (next),
        [count] "+w" (i)
      : [hi]    "r" (hi),
        [lo]    "r" (lo),
        [ptr]   "e" (ptr));
  }

#else
 #error "CPU SPEED NOT SUPPORTED"
#endif // end F_CPU ifdefs on __AVR__

// END AVR ----------------------------------------------------------------

#elif defined(__SAMD21G18A__) // Arduino Zero / CP Express

  // Tried this with a timer/counter, couldn't quite get adequate
  // resolution.  So yay, you get a load of goofball NOPs...

  uint8_t  *ptr, *end, p, bitMask, portNum;
  uint32_t  pinMask;

  portNum =  g_APinDescription[pin].ulPort;
  pinMask =  1ul << g_APinDescription[pin].ulPin;
  ptr     =  pixels;
  end     =  ptr + numBytes;
  p       = *ptr++;
  bitMask =  0x80;

  volatile uint32_t *set = &(PORT->Group[portNum].OUTSET.reg),
                    *clr = &(PORT->Group[portNum].OUTCLR.reg);

  if(is800KHz) {
    for(;;) {
      *set = pinMask;
      asm("nop; nop; nop; nop; nop; nop; nop; nop;");
      if(p & bitMask) {
        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop;");
        *clr = pinMask;
      } else {
        *clr = pinMask;
        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop;");
      }
      if(bitMask >>= 1) {
        asm("nop; nop; nop; nop; nop; nop; nop; nop; nop;");
      } else {
        if(ptr >= end) break;
        p       = *ptr++;
        bitMask = 0x80;
      }
    }
  } else { // 400 KHz bitstream
    for(;;) {
      *set = pinMask;
      asm("nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;");
      if(p & bitMask) {
        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop;");
        *clr = pinMask;
      } else {
        *clr = pinMask;
        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop; nop; nop; nop; nop; nop;"
            "nop; nop; nop;");
      }
      asm("nop; nop; nop; nop; nop; nop; nop; nop;"
          "nop; nop; nop; nop; nop; nop; nop; nop;"
          "nop; nop; nop; nop; nop; nop; nop; nop;"
          "nop; nop; nop; nop; nop; nop; nop; nop;");
      if(bitMask >>= 1) {
        asm("nop; nop; nop; nop; nop; nop; nop;");
      } else {
        if(ptr >= end) break;
        p       = *ptr++;
        bitMask = 0x80;
      }
    }
  }

#else
 #error "CPU ARCHITECTURE NOT SUPPORTED"
#endif

// END ARCHITECTURE SELECT ------------------------------------------------

  interrupts();
  endTime = micros(); // Save EOD time for latch on next call
}

/**************************************************************************/
/*! 
    @brief  Set the output pin number
    @param p the pin number
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::setPin(uint8_t p) {
  if(begun && (pin >= 0)) pinMode(pin, INPUT);
    pin = p;
    if(begun) {
      pinMode(p, OUTPUT);
      digitalWrite(p, LOW);
    }
#ifdef __AVR__
    port    = portOutputRegister(digitalPinToPort(p));
    pinMask = digitalPinToBitMask(p);
#endif
}

/**************************************************************************/
/*! 
    @brief  Set pixel color from separate R,G,B components:
    @param n the pixel number to set
    @param r the red component
    @param g the green component
    @param b the blue component
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::setPixelColor(
 uint16_t n, uint8_t r, uint8_t g, uint8_t b) {

  if(n < numLEDs) {
    if(brightness) { // See notes in setBrightness()
      r = (r * brightness) >> 8;
      g = (g * brightness) >> 8;
      b = (b * brightness) >> 8;
    }
    uint8_t *p;
    if(wOffset == rOffset) { // Is an RGB-type strip
      p = &pixels[n * 3];    // 3 bytes per pixel
    } else {                 // Is a WRGB-type strip
      p = &pixels[n * 4];    // 4 bytes per pixel
      p[wOffset] = 0;        // But only R,G,B passed -- set W to 0
    }
    p[rOffset] = r;          // R,G,B always stored
    p[gOffset] = g;
    p[bOffset] = b;
  }
}

/**************************************************************************/
/*! 
    @brief  Set pixel color from separate R,G,B,W components:
    @param n the pixel number to set
    @param r the red component
    @param g the green component
    @param b the blue component
    @param w the white component
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::setPixelColor(
 uint16_t n, uint8_t r, uint8_t g, uint8_t b, uint8_t w) {

  if(n < numLEDs) {
    if(brightness) { // See notes in setBrightness()
      r = (r * brightness) >> 8;
      g = (g * brightness) >> 8;
      b = (b * brightness) >> 8;
      w = (w * brightness) >> 8;
    }
    uint8_t *p;
    if(wOffset == rOffset) { // Is an RGB-type strip
      p = &pixels[n * 3];    // 3 bytes per pixel (ignore W)
    } else {                 // Is a WRGB-type strip
      p = &pixels[n * 4];    // 4 bytes per pixel
      p[wOffset] = w;        // Store W
    }
    p[rOffset] = r;          // Store R,G,B
    p[gOffset] = g;
    p[bOffset] = b;
  }
}

/**************************************************************************/
/*! 
    @brief  Set pixel color from 'packed' 32-bit RGB color:
    @param n the pixel number to set
    @param c the packed 32-bit color data
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::setPixelColor(uint16_t n, uint32_t c) {
  if(n < numLEDs) {
    uint8_t *p,
      r = (uint8_t)(c >> 16),
      g = (uint8_t)(c >>  8),
      b = (uint8_t)c;
    if(brightness) { // See notes in setBrightness()
      r = (r * brightness) >> 8;
      g = (g * brightness) >> 8;
      b = (b * brightness) >> 8;
    }
    if(wOffset == rOffset) {
      p = &pixels[n * 3];
    } else {
      p = &pixels[n * 4];
      uint8_t w = (uint8_t)(c >> 24);
      p[wOffset] = brightness ? ((w * brightness) >> 8) : w;
    }
    p[rOffset] = r;
    p[gOffset] = g;
    p[bOffset] = b;
  }
}

/**************************************************************************/
/*! 
    @brief  Convert separate R,G,B into packed 32-bit RGB color.
    @param r the red component
    @param g the green component
    @param b the blue component
    @return the converted 32-bit color

    @note Packed format is always RGB, regardless of LED strand color order.
*/
/**************************************************************************/
uint32_t Adafruit_CPlay_NeoPixel::Color(uint8_t r, uint8_t g, uint8_t b) {
  return ((uint32_t)r << 16) | ((uint32_t)g <<  8) | b;
}

/**************************************************************************/
/*! 
    @brief  Convert separate R,G,B,W into packed 32-bit WRGB color.
    @param r the red component
    @param g the green component
    @param b the blue component
    @param w the white component
    @return the converted 32-bit color

    @note Packed format is always WRGB, regardless of LED strand color order.
*/
/**************************************************************************/
uint32_t Adafruit_CPlay_NeoPixel::Color(uint8_t r, uint8_t g, uint8_t b, uint8_t w) {
  return ((uint32_t)w << 24) | ((uint32_t)r << 16) | ((uint32_t)g <<  8) | b;
}

/**************************************************************************/
/*! 
    @brief  Query color from previously-set pixel (returns packed 32-bit RGB value)
    @param n the number of the pixel to check
    @return the 32-bit color of the pixel

    @note this does not read from the pixel itself. It just checks the value that was previously set.
*/
/**************************************************************************/
uint32_t Adafruit_CPlay_NeoPixel::getPixelColor(uint16_t n) const {
  if(n >= numLEDs) return 0; // Out of bounds, return no color.

  uint8_t *p;

  if(wOffset == rOffset) { // Is RGB-type device
    p = &pixels[n * 3];
    if(brightness) {
      // Stored color was decimated by setBrightness().  Returned value
      // attempts to scale back to an approximation of the original 24-bit
      // value used when setting the pixel color, but there will always be
      // some error -- those bits are simply gone.  Issue is most
      // pronounced at low brightness levels.
      return (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
             (((uint32_t)(p[gOffset] << 8) / brightness) <<  8) |
             ( (uint32_t)(p[bOffset] << 8) / brightness       );
    } else {
      // No brightness adjustment has been made -- return 'raw' color
      return ((uint32_t)p[rOffset] << 16) |
             ((uint32_t)p[gOffset] <<  8) |
              (uint32_t)p[bOffset];
    }
  } else {                 // Is RGBW-type device
    p = &pixels[n * 4];
    if(brightness) { // Return scaled color
      return (((uint32_t)(p[wOffset] << 8) / brightness) << 24) |
             (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
             (((uint32_t)(p[gOffset] << 8) / brightness) <<  8) |
             ( (uint32_t)(p[bOffset] << 8) / brightness       );
    } else { // Return raw color
      return ((uint32_t)p[wOffset] << 24) |
             ((uint32_t)p[rOffset] << 16) |
             ((uint32_t)p[gOffset] <<  8) |
              (uint32_t)p[bOffset];
    }
  }
}


/**************************************************************************/
/*! 
    @brief  Returns pointer to pixels[] array.  Pixel data is stored in device-
      native format and is not translated here.  Application will need to be
      aware of specific pixel data format and handle colors appropriately.
    @return pointer to the pixel array.
*/
/**************************************************************************/
uint8_t *Adafruit_CPlay_NeoPixel::getPixels(void) const {
  return pixels;
}


/**************************************************************************/
/*! 
    @brief  get the number of pixels in the strip
    @return the number of pixels
*/
/**************************************************************************/
uint16_t Adafruit_CPlay_NeoPixel::numPixels(void) const {
  return numLEDs;
}

/**************************************************************************/
/*! 
    @brief  Adjust output brightness; 0=darkest (off), 255=brightest.
    @param b the brightness to set
    @return the number of pixels

    @note This does NOT immediately affect what's currently displayed on the LEDs.  The
      next call to show() will refresh the LEDs at this level.  However,
      this process is potentially "lossy," especially when increasing
      brightness.  The tight timing in the WS2811/WS2812 code means there
      aren't enough free cycles to perform this scaling on the fly as data
      is issued.  So we make a pass through the existing color data in RAM
      and scale it (subsequent graphics commands also work at this
      brightness level).  If there's a significant step up in brightness,
      the limited number of steps (quantization) in the old data will be
      quite visible in the re-scaled version.  For a non-destructive
      change, you'll need to re-render the full strip data.  C'est la vie.
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::setBrightness(uint8_t b) {
  // Stored brightness value is different than what's passed.
  // This simplifies the actual scaling math later, allowing a fast
  // 8x8-bit multiply and taking the MSB.  'brightness' is a uint8_t,
  // adding 1 here may (intentionally) roll over...so 0 = max brightness
  // (color values are interpreted literally; no scaling), 1 = min
  // brightness (off), 255 = just below max brightness.
  uint8_t newBrightness = b + 1;
  if(newBrightness != brightness) { // Compare against prior value
    // Brightness has changed -- re-scale existing data in RAM
    uint8_t  c,
            *ptr           = pixels,
             oldBrightness = brightness - 1; // De-wrap old brightness value
    uint16_t scale;
    if(oldBrightness == 0) scale = 0; // Avoid /0
    else if(b == 255) scale = 65535 / oldBrightness;
    else scale = (((uint16_t)newBrightness << 8) - 1) / oldBrightness;
    for(uint16_t i=0; i<numBytes; i++) {
      c      = *ptr;
      *ptr++ = (c * scale) >> 8;
    }
    brightness = newBrightness;
  }
}

/**************************************************************************/
/*! 
    @brief  get the global brightness value
    @return the global brightness
*/
/**************************************************************************/
uint8_t Adafruit_CPlay_NeoPixel::getBrightness(void) const {
  return brightness - 1;
}

/**************************************************************************/
/*! 
    @brief  set all neopixel data to 'off' in internal memory.
    @note this does not automatically update pixels. Update with show() after calling clear()
*/
/**************************************************************************/
void Adafruit_CPlay_NeoPixel::clear() {
  memset(pixels, 0, numBytes);
}

// This bizarre construct isn't Arduino code in the conventional sense.
// It exploits features of GCC's preprocessor to generate a PROGMEM
// table (in flash memory) holding an 8-bit unsigned sine wave (0-255).
static const int _SBASE_ = __COUNTER__ + 1; // Index of 1st __COUNTER__ below
#define _S1_ (sin((__COUNTER__ - _SBASE_) / 128.0 * M_PI) + 1.0) * 127.5 + 0.5,
#define _S2_ _S1_ _S1_ _S1_ _S1_ _S1_ _S1_ _S1_ _S1_ // Expands to 8 items
#define _S3_ _S2_ _S2_ _S2_ _S2_ _S2_ _S2_ _S2_ _S2_ // Expands to 64 items
static const uint8_t PROGMEM _sineTable[] = { _S3_ _S3_ _S3_ _S3_ }; // 256

// Similar to above, but for an 8-bit gamma-correction table.
#define _GAMMA_ 2.6
static const int _GBASE_ = __COUNTER__ + 1; // Index of 1st __COUNTER__ below
#define _G1_ pow((__COUNTER__ - _GBASE_) / 255.0, _GAMMA_) * 255.0 + 0.5,
#define _G2_ _G1_ _G1_ _G1_ _G1_ _G1_ _G1_ _G1_ _G1_ // Expands to 8 items
#define _G3_ _G2_ _G2_ _G2_ _G2_ _G2_ _G2_ _G2_ _G2_ // Expands to 64 items
static const uint8_t PROGMEM _gammaTable[] = { _G3_ _G3_ _G3_ _G3_ }; // 256

/*!  @brief Get a sinusoidal value from a sine table
     @param x a 0 to 255 value corresponding to an index to the sine table
     @returns An 8-bit sinusoidal value back */
uint8_t Adafruit_CPlay_NeoPixel::sine8(uint8_t x) const {
  return pgm_read_byte(&_sineTable[x]); // 0-255 in, 0-255 out
}

/*!  @brief Get a gamma-corrected value from a gamma table
     @param x a 0 to 255 value corresponding to an index to the gamma table
     @returns An 8-bit gamma-corrected value back */
uint8_t Adafruit_CPlay_NeoPixel::gamma8(uint8_t x) const {
  return pgm_read_byte(&_gammaTable[x]); // 0-255 in, 0-255 out
}