Function initPluGraph

src/platforms/arm/lpc/clockless_arm_lpc_plu.h:234–277

One-shot PLU init. Idempotent: a second call rewrites the same registers.

// One-shot PLU init. Idempotent: a second call rewrites the same registers.
static void initPluGraph() FL_NOEXCEPT {
    // Step 1: enable peripheral clock BEFORE any register write
    // (ARM Cortex-M0+ silently drops writes to unpowered peripherals).
    enablePluClock();

    // Step 2: wire LUT0 inputs - only IN2 matters.
    writeLutInputMux(0, 0, kMuxPluIn0);   // ignored
    writeLutInputMux(0, 1, kMuxPluIn1);   // ignored
    writeLutInputMux(0, 2, kMuxPluIn2);   // CNT1
    writeLutInputMux(0, 3, kMuxPluIn0);
    writeLutInputMux(0, 4, kMuxPluIn0);
    writeLutTruth(0, kLut0Truth_T0H);

    // Step 3: wire LUT1 inputs - IN1, IN2 matter.
    writeLutInputMux(1, 0, kMuxPluIn0);   // ignored
    writeLutInputMux(1, 1, kMuxPluIn1);   // CNT0
    writeLutInputMux(1, 2, kMuxPluIn2);   // CNT1
    writeLutInputMux(1, 3, kMuxPluIn0);
    writeLutInputMux(1, 4, kMuxPluIn0);
    writeLutTruth(1, kLut1Truth_T1H);

    // Step 4: wire LUT2 (bit mux) - IN0=DATA, IN1=LUT0_out, IN2=LUT1_out.
    writeLutInputMux(2, 0, kMuxPluIn0);     // DATA
    writeLutInputMux(2, 1, muxLutOutput(0)); // LUT0 out
    writeLutInputMux(2, 2, muxLutOutput(1)); // LUT1 out
    writeLutInputMux(2, 3, kMuxPluIn0);
    writeLutInputMux(2, 4, kMuxPluIn0);
    writeLutTruth(2, kLut2Truth_BitMux);

    // Step 5: route LUT2 to PLU_OUT0.
    writeOutputMux(0, 2);

    // Step 6: PLU is purely combinational + a wake-int block we don't use.
    // Disable any latent wake-interrupt config (UM11065 §12.6.4).
    *reg32(kPluBase, kOffWakeIntCtrl) = 0;

    // Step 7 (deferred): bring up the timing-counter source feeding PLU_IN1 /
    // PLU_IN2. On LPC804 this is most naturally an SCT-generated Gray-coded
    // pair (counter rolls every WS2812 bit period). The exact SCT config is
    // pin-routing dependent and intentionally left for board-level glue.
    // TODO(2841): provide a default SCT-based timing source in a follow-up
    // commit; for now the integrator must call their own init_timing_source()
    // before FastLED.show().
}

}  // namespace lpc_plu_detail