buildWave3ExpansionLUT()

FL_OPTIMIZE_FUNCTION Wave3BitExpansionLut fl::buildWave3ExpansionLUT

(

const ChipsetTiming &

timing

)

Build a Wave3BitExpansionLut from chipset timing data.

Converts three-phase LED timing (T1, T2, T3) into a nibble lookup table for 3-tick-per-bit waveform expansion. Each nibble maps to 12 bits.

Parameters

timing

ChipsetTiming struct containing T1, T2, T3 in nanoseconds

Returns

Populated Wave3BitExpansionLut lookup table (32 bytes)

Definition at line 70 of file wave3.cpp.hpp.

                                                                                      {
    Wave3BitExpansionLut lut;
 
    const u32 period = timing.T1 + timing.T2 + timing.T3;
 
    // T0H = T1, T1H = T1 + T2
    const float t0h_norm = static_cast<float>(timing.T1) / period;
    const float t1h_norm = static_cast<float>(timing.T1 + timing.T2) / period;
 
    // Round to nearest integer tick count out of 3
    u32 ticks_bit0 = static_cast<u32>(t0h_norm * 3.0f + 0.5f);
    u32 ticks_bit1 = static_cast<u32>(t1h_norm * 3.0f + 0.5f);
 
    // Clamp to valid range [0, 3]
    if (ticks_bit0 > 3) ticks_bit0 = 3;
    if (ticks_bit1 > 3) ticks_bit1 = 3;
 
    // Generate 3-bit patterns for bit 0 and bit 1
    // Pattern has ticks_bitN high bits followed by (3 - ticks_bitN) low bits
    // MSB first within the 3-bit field
    u8 pattern_bit0 = 0;
    u8 pattern_bit1 = 0;
 
    for (u32 i = 0; i < ticks_bit0; i++) {
        pattern_bit0 |= (0x4 >> i); // Set bits from MSB: 0x4=100, 0x6=110, 0x7=111
    }
    for (u32 i = 0; i < ticks_bit1; i++) {
        pattern_bit1 |= (0x4 >> i);
    }
 
    // Build LUT for all 16 nibbles
    // Each nibble maps to 12 bits (4 LED bits × 3 ticks each)
    for (u8 nibble = 0; nibble < 16; nibble++) {
        u16 pattern = 0;
        // Process bits MSB first (bit 3, 2, 1, 0)
        for (int bit_pos = 3; bit_pos >= 0; bit_pos--) {
            bool bit_set = (nibble >> bit_pos) & 1;
            u8 tick_pattern = bit_set ? pattern_bit1 : pattern_bit0;
            pattern = (pattern << 3) | (tick_pattern & 0x7);
        }
        lut.lut[nibble] = pattern;
    }
 
    return lut;
}

References FL_NO_EXCEPT.