Michel/arduino-library-lolshield
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For SHADES==2 or 8, use precomputed exponents. Saves 716 bytes of code for

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SHADES==8; the compiler already optimized to ~the same code for SHADES==2,
so there is no change there.
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2013-08-27 03:43:29 +00:00
parent 72c03d0a77
commit b323909c49
1 changed files with 25 additions and 5 deletions
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lib/Charliplexing.cpp
+25 -5
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@@ -423,15 +423,35 @@ void LedSign::SetBrightness(uint8_t brightness)
/* ---- This needs review! Please review. -- thilo */
// set up page counts
// TODO: make SHADES a function parameter. This would require some refactoring.
const int max = 255;
const float scale = 1.8;
const float delta = pow(max, 1.0 / scale) / (SHADES - 1);
int counts[SHADES];
uint8_t i;
const int max = 255;
#define C(x) (0.49999f + max * brightnessPercent * fastPrescaler.relativeSpeed * x)
#if SHADES == 2
const int counts[SHADES] = {
0.0f,
C(1.0f),
};
#elif SHADES == 8
const int counts[SHADES] = {
0.0f,
C(0.030117819624378613658712f),
C(0.104876339357015456218728f),
C(0.217591430058779512857041f),
C(0.365200625214741116475101f),
C(0.545719579451565749226202f),
C(0.757697368024318811680598f),
C(1.0f),
};
#else
// NOTE: Changing "scale" invalidates any tables above!
const float scale = 1.8f;
const float delta = pow(max, 1.0f / scale) / (SHADES - 1);
int counts[SHADES];
counts[0] = 0;
for (i=1; i<SHADES; i++)
counts[i] = pow(i * delta, scale) * brightnessPercent * fastPrescaler.relativeSpeed + 0.49999;
counts[i] = pow(i * delta, scale) * brightnessPercent * fastPrescaler.relativeSpeed + 0.49999f;
#endif
// Wait until the previous brightness request goes through
while( videoFlipTimer ) {