Elevator System Using a Microprocessor

An elevator system implemented using an assembly-coded microprocessor (Freescale/NXP HCS12 family). The controller is written in HC12 assembly and implements a multi-floor elevator with LED indicators, PWM motor control, LCD messages, and safety checks.

Microprocessor / MCU

The project targets the MC9S12DT256 (HCS12) microcontroller. This is specified in the derivative include file:

; include derivative specific macros
INCLUDE 'mc9s12dt256.inc'

Project Structure

• Sources/main.asm – Main controller logic (FSM, PWM motor drive, LED/LCD control)
• Sources/derivative.inc – MCU include (MC9S12DT256)
• Project_6.mcp – CodeWarrior project file
• bin/ – Build outputs and debug artifacts
• Prototype/ – Images and demo videos

How It Works (Logic Overview)

The elevator is implemented as a finite state machine (FSM). The FSM represents elevator states (idle, moving up/down to specific floors, weight alarm). The state variable (FSM) is compared in the main loop to decide which sequence to run.

Key FSM meanings are documented directly in the source:

FSM         DC.B  0                   ; THIS VARIABLE CONTROLS THE FINITE STATE MACHINE WHICH TELLS ME THE INSTRUCTIONS TO PERFORM
                                      ; $00 --> IDLE
                                      ; $FF --> WEIGHT RESTRICTIONS
                                      ; $01 --> MOVING TO FL1 UP      FORM GF       (FL01)
                                      ; $02 --> MOVING TO FL2 UP                    (FL02)
                                      ; $03 --> MOVING TO FL1 THEN 2                (FL012)
                                      ; $04 --> MOVING TO FL2 UP      FROM FL1      (FL12)
                                      ; $05 --> MOVING TO GF  DOWN                  (FL10)
                                      ; $06 --> MOVING TO FL2 THEN GF               (FL120)
                                      ; $07 --> MOVING TO FL1 DOWN    FROM FL2      (FL21)
                                      ; $08 --> MOVING TO GF  DOWN                  (FL20)
                                      ; $09 --> MOVING TO FL1 THEN GF               (FL210)

The main loop checks FSM and jumps to the appropriate routine:

mainLoop:
            LDAA  FSM
            CMPA  #00
            LBEQ  STP
            CMPA  #$FF                
            LBEQ  ALRM            
            CMPA  #$01
            LBEQ  F01
            CMPA  #$02
            LBEQ  F02            
            CMPA  #$03
            LBEQ  F012            
            CMPA  #$04
            LBEQ  F12            
            CMPA  #$05
            LBEQ  F10            
            CMPA  #$06
            LBEQ  F120            
            CMPA  #$07
            LBEQ  F21            
            CMPA  #$08
            LBEQ  F20
            JMP   F210

Inputs / Outputs (High-Level)

• Buttons / PORTA: Used to select floor and movement combinations.
• PWM channels: Drive the motor (direction and speed).
• LEDs: Indicate movement, alarms, or status.
• LCD: Displays textual status (e.g., floor, moving up/down).
• Potentiometer: Used as a weight/overload sensor and triggers alarm logic.

How to Use / Build

1. Open Project_6.mcp in Freescale CodeWarrior for HCS12/HC12.
2. Ensure the MCU derivative is set to MC9S12DT256.
3. Build the project (outputs appear in bin/).
4. Flash/load the generated .s19 file to the HCS12 board.

Prototype Media

Prototype Image

Demo Videos

• Presentation (MP4)
• Video 1 (MP4)

If the videos do not play inline on GitHub, click the links to open/download them.

Notes

• The system is designed around 3 floors: ground, floor 1, floor 2.
• The FSM ensures deterministic transitions between elevator states.
• Overweight/unsafe conditions trigger a dedicated alarm state.

License

See LICENSE.