Embedded Systems Programming, Networks, Prof. Shankar (17), Study notes of Embedded Systems Programming

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Networks 

Example: elevator controller.

Terminology 

 Elevator carHoistway: elevator shaft.: holds passengers.

  Car control panel car. : buttons in each

Floor control panel etc. per floor. : elevator request,

Theory of operation 

 Each floor has control panel, display.Each car has control panel:

 ^ ^ one button per floor;emergency stop.

Controlled by a single controller.

Elevator position sensing

coarse

sensor fine

Elevator system requirements

name inputs outputs elevator systemF floor control, N position, N car control, 1 masterF displays, N motor controllers functions performance manufacturing cost responds to requests, operates safelyelevator control is time-criticalelectronics is small part of total power physical size/weight electronics consumes small fraction of totalcabling is important

Elevator system class diagram

Car Floor

Master-control-panel* Controller Motor*

Coarse-sensor* Fine-sensor*

Floor-control-panel^ Car-control-panel

(^11) (^1) N

1 F^1

N 1

(^11) (^11 ) 1 1

Car and Floor classes

Car request-lights[1..F]: boolean current-floor: integer

Floor up-light, down-light: boolean

Controller class

Controller car-floor[1..H]: integer emergency-stop[1..H]: scan-cars() scan-floors()^ integer scan-master-panel() operate()

Panels and cab controller 

 Panels are straightforward---no real-^ time requirements.Cab controller:

  (^) read buttons and send events to system controller;read sensor inputs and send to system controller.

System controller 

Must take inputs from many sources:   car controllers;floors.

  Must control cars to hard real-time deadlines.

User interface, scheduling are soft deadlines.