Method pollOnce

src/platforms/arm/lpc/rx_sct_capture.cpp.hpp:485–542

}

fl::size LpcSctRxChannel::pollOnce() FL_NOEXCEPT {
#if defined(FASTLED_LPC_RX_SCT) && defined(FL_IS_ARM_LPC_845)
    // Drain SCT EVFLAG into the edge buffer. For each event that has
    // fired since the last poll:
    //   * EV0 (rising-edge capture) → read CAP[0]. If we already saw a
    //     prior edge, the line was LOW from `mPrevTick` to `tick` (since
    //     this is a rising edge, so it was LOW before).
    //   * EV1 (falling-edge capture) → read CAP[1]. Line was HIGH from
    //     `mPrevTick` to `tick`.
    //
    // The "phase level" labeled into EdgeTime.high is the level the line
    // was at DURING the just-completed phase, not the edge direction.
    // That matches the decoder's expectation: HIGH duration then LOW
    // duration per WS2812 bit.
    //
    // We deliberately don't clear EVFLAG until AFTER reading CAP[n]; the
    // SCT latches a fresh CAP[n] on the *next* matching edge regardless
    // of the EVFLAG bit, so the read/W1C order matters only for the
    // poll-once semantic (one capture per poll-cycle per event).

    fl::size pushed = 0;
    const fl::u32 evflag = sct(kOffEVFLAG);

    if (evflag & 0x1u) {
        const fl::u32 tick = sct_cap(0);
        sct(kOffEVFLAG) = 0x1u;  // W1C
        if (mPrevSeen) {
            const fl::u32 delta = tick - mPrevTick;   // u32 wrap is fine — modulo arithmetic over 32-bit counter
            if (mEdges.size() < mCapacity) {
                mEdges.push_back(EdgeTime(mLastRising, ticksToNs(delta)));
                ++pushed;
            }
        }
        mPrevTick = tick;
        mPrevSeen = true;
        mLastRising = true;  // a rising edge just fired → line was LOW before, HIGH now
    }

    if (evflag & 0x2u) {
        const fl::u32 tick = sct_cap(1);
        sct(kOffEVFLAG) = 0x2u;
        if (mPrevSeen) {
            const fl::u32 delta = tick - mPrevTick;
            if (mEdges.size() < mCapacity) {
                mEdges.push_back(EdgeTime(mLastRising, ticksToNs(delta)));
                ++pushed;
            }
        }
        mPrevTick = tick;
        mPrevSeen = true;
        mLastRising = false;
    }

    return pushed;
#else
    return 0;
#endif
}