def u4(bytes):
    """
    Convert a little endian Ublox U4 type to a native integer
    """
    if len(bytes) != 4:
        raise ValueError('Need exactly 4 bytes')
    return int(bytes[0]) + \
        int(bytes[1]) * 256 + \
        int(bytes[2]) * 65536 + \
        int(bytes[3]) * 16777216