implemented calc_pos_with_const_speed() helper function and successfully tested with constant speed and no acceleration.
added overshoot correction to elevator position algorithm.
added elev_move_state_t enum.
updated position helper functions.
updated calculation resolution, implemented a loop counter named 'iter' to determine when 500ms has elapsed and update should be given.
cleaned up unused code.
added binding for open and close buttons.
added check to open_door() function to ensure elevator is stopped before opening door.
added FIXME note for problem with operate_door() functionality.