Method transmitSpi

src/platforms/shared/bitbang/bitbang_channel_driver.cpp.hpp:216–292

}

void BitBangChannelDriver::transmitSpi(
    fl::span<const ChannelDataPtr> channels) FL_NOEXCEPT {
    if (channels.empty()) return;

    // Group channels by clock pin
    fl::vector<bool> processed(channels.size(), false);

    for (fl::size i = 0; i < channels.size(); ++i) {
        if (processed[i] || !channels[i] || !channels[i]->isSpi()) continue;

        const auto* spiCfg =
            channels[i]->getChipset().ptr<SpiChipsetConfig>();
        if (!spiCfg) continue;

        int clockPin = spiCfg->clockPin;
        u32 clockHz = spiCfg->timing.clock_hz;
        u32 halfPeriodNs = (clockHz > 0) ? (500000000u / clockHz) : 500u;

        // Collect all channels sharing this clock pin
        fl::vector<fl::size> groupIndices;
        groupIndices.push_back(i);
        processed[i] = true;

        for (fl::size j = i + 1; j < channels.size(); ++j) {
            if (processed[j] || !channels[j] || !channels[j]->isSpi()) continue;
            const auto* otherSpi =
                channels[j]->getChipset().ptr<SpiChipsetConfig>();
            if (otherSpi && otherSpi->clockPin == clockPin) {
                groupIndices.push_back(j);
                processed[j] = true;
            }
        }

        // Find max data size in group
        size_t maxBytes = 0;
        for (fl::size gi = 0; gi < groupIndices.size(); ++gi) {
            size_t sz = channels[groupIndices[gi]]->getSize();
            if (sz > maxBytes) maxBytes = sz;
        }

        // Bit-bang SPI: MSB-first, data before rising edge (mode 0)
        for (size_t byteIdx = 0; byteIdx < maxBytes; ++byteIdx) {
            for (int bit = 7; bit >= 0; --bit) {
                // Build data mask for all lanes
                u8 dataMask = 0;
                for (fl::size gi = 0; gi < groupIndices.size(); ++gi) {
                    const auto& ch = channels[groupIndices[gi]];
                    const auto* chSpi =
                        ch->getChipset().ptr<SpiChipsetConfig>();
                    if (!chSpi) continue;

                    int pin = chSpi->dataPin;
                    if (pin < 0 || pin > 255) continue;
                    int slot = mSlotForPin[pin];
                    if (slot < 0) continue;

                    const auto& data = ch->getData();
                    u8 byte = (byteIdx < data.size()) ? data[byteIdx] : 0;