Method flushInternal

Drivers/EPDiyDisplay/Source/EpdiyDisplay.cpp:348–404

Internal functions

// Internal functions
void EpdiyDisplay::flushInternal(const lv_area_t* area, uint8_t* pixelMap, bool isLast) {
    if (!initialized) {
        LOG_E(TAG, "Cannot flush - EPD not initialized");
        return;
    }

    if (!powered) {
        setPowerOn(true);
    }

    const int x = area->x1;
    const int y = area->y1;
    const int width = lv_area_get_width(area);
    const int height = lv_area_get_height(area);

    LOG_D(TAG, "Flushing area: x=%d, y=%d, w=%d, h=%d isLast=%d", x, y, width, height, (int)isLast);

    // Convert L8 (8-bit grayscale, 0=black/255=white) to EPDiy 4-bit (0=black/15=white).
    // Pack 2 pixels per byte: lower nibble = even column, upper nibble = odd column.
    // Row stride includes one padding nibble for odd widths to keep rows aligned.
    // Threshold at 128 (matching FastEPD BB_MODE_1BPP): pixels > 127 → full white (15),
    // pixels ≤ 127 → full black (0).  Maximum contrast for the Mono theme and correct for
    // MODE_DU which only drives two levels.  For greyscale content / MODE_GL16, replace
    // the threshold with `src[col] >> 4` to preserve intermediate grey levels.
    const int row_stride = (width + 1) / 2;
    for (int row = 0; row < height; ++row) {
        const uint8_t* src = pixelMap + static_cast<size_t>(row) * width;
        uint8_t* dst = packedBuffer + static_cast<size_t>(row) * row_stride;
        for (int col = 0; col < width; col += 2) {
            const uint8_t p0 = (src[col] > 127) ? 15u : 0u;
            const uint8_t p1 = (col + 1 < width) ? ((src[col + 1] > 127) ? 15u : 0u) : 0u;
            dst[col / 2] = static_cast<uint8_t>((p1 << 4) | p0);
        }
    }

    const EpdRect update_area = {
        .x = x,
        .y = y,
        .width = static_cast<uint16_t>(width),
        .height = static_cast<uint16_t>(height)
    };

    // Write pixels into EPDiy's framebuffer (no hardware I/O, just memory)
    epd_draw_rotated_image(update_area, packedBuffer, framebuffer);

    // Only trigger EPD hardware update on the last flush of this render cycle.
    // EPDiy's epd_prep tasks run at configMAX_PRIORITIES-1 with busy-wait loops; calling
    // epd_hl_update_area on every partial flush starves IDLE and triggers the task watchdog
    // during scroll animations. Batching to one hardware update per LVGL render cycle fixes this.
    if (isLast) {
        epd_hl_update_screen(
            &highlevelState,
            static_cast<EpdDrawMode>(configuration->defaultDrawMode | MODE_PACKING_2PPB),
            configuration->defaultTemperature
        );
    }
}