pub const PACK_DIR_1: u32 = 0x01;
Pack from MSB first. For image data, 0x11, 0x22, 0x33, 0x44, it will appear as 0x11223344 in RX FIFO. For stat data, 0xAAAA, 0xBBBB, it will appear as 0xAAAABBBB in STAT FIFO.