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/*
* Fadecandy Firmware: Low-level draw buffer update code
* (Included into fadecandy.cpp)
*
* Copyright (c) 2013 Micah Elizabeth Scott
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
static void updateDrawBuffer(unsigned interpCoefficient)
{
/*
* Update the LED draw buffer. In one step, we do the interpolation,
* gamma correction, dithering, and we convert packed-pixel data to the
* planar format used for OctoWS2811 DMAs.
*
* "interpCoefficient" indicates how far between fbPrev and fbNext
* we are. It is a fixed point value in the range [0x0000, 0x10000],
* corresponding to 100% fbPrev and 100% fbNext, respectively.
*/
// For each pixel, this is a 24-byte stream of bits (6 words)
uint32_t *out = (uint32_t*) leds.getDrawBuffer();
/*
* Interpolation coefficients, including a multiply by 257 to convert 8-bit color to 16-bit color.
* You'd think that it would save clock cycles to calculate icPrev in updatePixel(), but this doesn't
* seem to be the case.
*
* icPrev in range [0, 0x1010000]
* icNext in range [0, 0x1010000]
* icPrev + icNext = 0x1010000
*/
uint32_t icPrev = 257 * (0x10000 - interpCoefficient);
uint32_t icNext = 257 * interpCoefficient;
/*
* Pointer to the residual buffer for this pixel. Calculating this here rather than in updatePixel
* saves a lot of clock cycles, since otherwise updatePixel() immediately needs to do a load from
* constant pool and some multiplication.
*/
residual_t *pResidual = residual;
for (int i = 0; i < LEDS_PER_STRIP; ++i, pResidual += 3) {
// Six output words
union {
uint32_t word;
struct {
uint32_t p0a:1, p1a:1, p2a:1, p3a:1, p4a:1, p5a:1, p6a:1, p7a:1,
p0b:1, p1b:1, p2b:1, p3b:1, p4b:1, p5b:1, p6b:1, p7b:1,
p0c:1, p1c:1, p2c:1, p3c:1, p4c:1, p5c:1, p6c:1, p7c:1,
p0d:1, p1d:1, p2d:1, p3d:1, p4d:1, p5d:1, p6d:1, p7d:1;
};
} o0, o1, o2, o3, o4, o5;
/*
* Remap bits.
*
* This generates compact and efficient code using the BFI instruction.
*/
uint32_t p0 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 0),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 0),
pResidual + LEDS_PER_STRIP * 3 * 0);
o5.p0d = p0;
o5.p0c = p0 >> 1;
o5.p0b = p0 >> 2;
o5.p0a = p0 >> 3;
o4.p0d = p0 >> 4;
o4.p0c = p0 >> 5;
o4.p0b = p0 >> 6;
o4.p0a = p0 >> 7;
o3.p0d = p0 >> 8;
o3.p0c = p0 >> 9;
o3.p0b = p0 >> 10;
o3.p0a = p0 >> 11;
o2.p0d = p0 >> 12;
o2.p0c = p0 >> 13;
o2.p0b = p0 >> 14;
o2.p0a = p0 >> 15;
o1.p0d = p0 >> 16;
o1.p0c = p0 >> 17;
o1.p0b = p0 >> 18;
o1.p0a = p0 >> 19;
o0.p0d = p0 >> 20;
o0.p0c = p0 >> 21;
o0.p0b = p0 >> 22;
o0.p0a = p0 >> 23;
uint32_t p1 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 1),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 1),
pResidual + LEDS_PER_STRIP * 3 * 1);
o5.p1d = p1;
o5.p1c = p1 >> 1;
o5.p1b = p1 >> 2;
o5.p1a = p1 >> 3;
o4.p1d = p1 >> 4;
o4.p1c = p1 >> 5;
o4.p1b = p1 >> 6;
o4.p1a = p1 >> 7;
o3.p1d = p1 >> 8;
o3.p1c = p1 >> 9;
o3.p1b = p1 >> 10;
o3.p1a = p1 >> 11;
o2.p1d = p1 >> 12;
o2.p1c = p1 >> 13;
o2.p1b = p1 >> 14;
o2.p1a = p1 >> 15;
o1.p1d = p1 >> 16;
o1.p1c = p1 >> 17;
o1.p1b = p1 >> 18;
o1.p1a = p1 >> 19;
o0.p1d = p1 >> 20;
o0.p1c = p1 >> 21;
o0.p1b = p1 >> 22;
o0.p1a = p1 >> 23;
uint32_t p2 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 2),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 2),
pResidual + LEDS_PER_STRIP * 3 * 2);
o5.p2d = p2;
o5.p2c = p2 >> 1;
o5.p2b = p2 >> 2;
o5.p2a = p2 >> 3;
o4.p2d = p2 >> 4;
o4.p2c = p2 >> 5;
o4.p2b = p2 >> 6;
o4.p2a = p2 >> 7;
o3.p2d = p2 >> 8;
o3.p2c = p2 >> 9;
o3.p2b = p2 >> 10;
o3.p2a = p2 >> 11;
o2.p2d = p2 >> 12;
o2.p2c = p2 >> 13;
o2.p2b = p2 >> 14;
o2.p2a = p2 >> 15;
o1.p2d = p2 >> 16;
o1.p2c = p2 >> 17;
o1.p2b = p2 >> 18;
o1.p2a = p2 >> 19;
o0.p2d = p2 >> 20;
o0.p2c = p2 >> 21;
o0.p2b = p2 >> 22;
o0.p2a = p2 >> 23;
uint32_t p3 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 3),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 3),
pResidual + LEDS_PER_STRIP * 3 * 3);
o5.p3d = p3;
o5.p3c = p3 >> 1;
o5.p3b = p3 >> 2;
o5.p3a = p3 >> 3;
o4.p3d = p3 >> 4;
o4.p3c = p3 >> 5;
o4.p3b = p3 >> 6;
o4.p3a = p3 >> 7;
o3.p3d = p3 >> 8;
o3.p3c = p3 >> 9;
o3.p3b = p3 >> 10;
o3.p3a = p3 >> 11;
o2.p3d = p3 >> 12;
o2.p3c = p3 >> 13;
o2.p3b = p3 >> 14;
o2.p3a = p3 >> 15;
o1.p3d = p3 >> 16;
o1.p3c = p3 >> 17;
o1.p3b = p3 >> 18;
o1.p3a = p3 >> 19;
o0.p3d = p3 >> 20;
o0.p3c = p3 >> 21;
o0.p3b = p3 >> 22;
o0.p3a = p3 >> 23;
uint32_t p4 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 4),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 4),
pResidual + LEDS_PER_STRIP * 3 * 4);
o5.p4d = p4;
o5.p4c = p4 >> 1;
o5.p4b = p4 >> 2;
o5.p4a = p4 >> 3;
o4.p4d = p4 >> 4;
o4.p4c = p4 >> 5;
o4.p4b = p4 >> 6;
o4.p4a = p4 >> 7;
o3.p4d = p4 >> 8;
o3.p4c = p4 >> 9;
o3.p4b = p4 >> 10;
o3.p4a = p4 >> 11;
o2.p4d = p4 >> 12;
o2.p4c = p4 >> 13;
o2.p4b = p4 >> 14;
o2.p4a = p4 >> 15;
o1.p4d = p4 >> 16;
o1.p4c = p4 >> 17;
o1.p4b = p4 >> 18;
o1.p4a = p4 >> 19;
o0.p4d = p4 >> 20;
o0.p4c = p4 >> 21;
o0.p4b = p4 >> 22;
o0.p4a = p4 >> 23;
uint32_t p5 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 5),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 5),
pResidual + LEDS_PER_STRIP * 3 * 5);
o5.p5d = p5;
o5.p5c = p5 >> 1;
o5.p5b = p5 >> 2;
o5.p5a = p5 >> 3;
o4.p5d = p5 >> 4;
o4.p5c = p5 >> 5;
o4.p5b = p5 >> 6;
o4.p5a = p5 >> 7;
o3.p5d = p5 >> 8;
o3.p5c = p5 >> 9;
o3.p5b = p5 >> 10;
o3.p5a = p5 >> 11;
o2.p5d = p5 >> 12;
o2.p5c = p5 >> 13;
o2.p5b = p5 >> 14;
o2.p5a = p5 >> 15;
o1.p5d = p5 >> 16;
o1.p5c = p5 >> 17;
o1.p5b = p5 >> 18;
o1.p5a = p5 >> 19;
o0.p5d = p5 >> 20;
o0.p5c = p5 >> 21;
o0.p5b = p5 >> 22;
o0.p5a = p5 >> 23;
uint32_t p6 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 6),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 6),
pResidual + LEDS_PER_STRIP * 3 * 6);
o5.p6d = p6;
o5.p6c = p6 >> 1;
o5.p6b = p6 >> 2;
o5.p6a = p6 >> 3;
o4.p6d = p6 >> 4;
o4.p6c = p6 >> 5;
o4.p6b = p6 >> 6;
o4.p6a = p6 >> 7;
o3.p6d = p6 >> 8;
o3.p6c = p6 >> 9;
o3.p6b = p6 >> 10;
o3.p6a = p6 >> 11;
o2.p6d = p6 >> 12;
o2.p6c = p6 >> 13;
o2.p6b = p6 >> 14;
o2.p6a = p6 >> 15;
o1.p6d = p6 >> 16;
o1.p6c = p6 >> 17;
o1.p6b = p6 >> 18;
o1.p6a = p6 >> 19;
o0.p6d = p6 >> 20;
o0.p6c = p6 >> 21;
o0.p6b = p6 >> 22;
o0.p6a = p6 >> 23;
uint32_t p7 = updatePixel(icPrev, icNext,
buffers.fbPrev->pixel(i + LEDS_PER_STRIP * 7),
buffers.fbNext->pixel(i + LEDS_PER_STRIP * 7),
pResidual + LEDS_PER_STRIP * 3 * 7);
o5.p7d = p7;
o5.p7c = p7 >> 1;
o5.p7b = p7 >> 2;
o5.p7a = p7 >> 3;
o4.p7d = p7 >> 4;
o4.p7c = p7 >> 5;
o4.p7b = p7 >> 6;
o4.p7a = p7 >> 7;
o3.p7d = p7 >> 8;
o3.p7c = p7 >> 9;
o3.p7b = p7 >> 10;
o3.p7a = p7 >> 11;
o2.p7d = p7 >> 12;
o2.p7c = p7 >> 13;
o2.p7b = p7 >> 14;
o2.p7a = p7 >> 15;
o1.p7d = p7 >> 16;
o1.p7c = p7 >> 17;
o1.p7b = p7 >> 18;
o1.p7a = p7 >> 19;
o0.p7d = p7 >> 20;
o0.p7c = p7 >> 21;
o0.p7b = p7 >> 22;
o0.p7a = p7 >> 23;
*(out++) = o0.word;
*(out++) = o1.word;
*(out++) = o2.word;
*(out++) = o3.word;
*(out++) = o4.word;
*(out++) = o5.word;
}
}