encoder_utils.h

Go to the documentation of this file.

#pragma once

 
#include "fl/stl/stdint.h"
#include "fl/gfx/gamma_lut.h"
#include "fl/stl/noexcept.h"
 
namespace fl {

inline u8 mapBrightness8to5(u8 brightness_8bit) FL_NOEXCEPT {
    #if defined(FL_IS_AVR)
    // AVR-specific: Use bit shifts to avoid expensive division
    // Approximation: (value * 31) / 255 ≈ (value * 31) >> 8
    // Add rounding: ((value * 31) + 128) >> 8
    u16 bri5 = ((u16)brightness_8bit * 31 + 128) >> 8;
 
    // Ensure non-zero input doesn't map to zero output
    if (bri5 == 0 && brightness_8bit != 0) {
        bri5 = 1;
    }
 
    return static_cast<u8>(bri5);
    #else
    // Non-AVR: Use accurate division
    u16 bri5 = ((u16)brightness_8bit * 31 + 128) / 255;
 
    // Ensure non-zero input doesn't map to zero output
    if (bri5 == 0 && brightness_8bit != 0) {
        bri5 = 1;
    }
 
    return static_cast<u8>(bri5);
    #endif
}

inline u8 p9813FlagByte(u8 r, u8 g, u8 b) FL_NOEXCEPT {
    return 0xC0 | ((~b & 0xC0) >> 2) | ((~g & 0xC0) >> 4) | ((~r & 0xC0) >> 6);
}

inline u8 lpd8806Encode(u8 value) FL_NOEXCEPT {
    // LPD8806 requires MSB set on each byte, and uses 7-bit color depth
    return 0x80 | ((value >> 1) | ((value && (value < 254)) & 0x01));
}

inline u16 hd108GammaCorrect(u8 value) FL_NOEXCEPT {
    return Gamma28LUT16::read(value);
}

inline void hd108BrightnessHeader(u8 brightness_8bit, u8* f0_out, u8* f1_out) FL_NOEXCEPT {
    (void)brightness_8bit;  // Unused - brightness applied to 16-bit values instead
 
    // Use maximum gain for all channels for maximum precision
    // Brightness control happens via 16-bit PWM values
    constexpr u8 r_gain = 31;
    constexpr u8 g_gain = 31;
    constexpr u8 b_gain = 31;
 
    // Correct HD108 per-channel encoding:
    // f0: [1][RRRRR][GG] - marker bit, 5-bit R gain, 2 MSBs of G gain
    // f1: [GGG][BBBBB]   - 3 LSBs of G gain, 5-bit B gain
    *f0_out = 0x80 | ((r_gain & 0x1F) << 2) | ((g_gain >> 3) & 0x03);
    *f1_out = ((g_gain & 0x07) << 5) | (b_gain & 0x1F);
}

inline u16 lpd6803EncodeRGB(u8 r, u8 g, u8 b) FL_NOEXCEPT {
    u16 command = 0x8000;  // Start marker
    command |= (r & 0xF8) << 7;   // Red: high 5 bits
    command |= (g & 0xF8) << 2;   // Green: high 5 bits
    command |= (b >> 3);          // Blue: high 5 bits
    return command;
}
 
} // namespace fl