Hierarchical state machine concept in Embedded C - Mini Project: Build & Apply

Hierarchical State Machine Concept in Embedded C

📖 Scenario: You are building a simple control system for a home heating device. The device has two main modes: Off and On. When it is On, it can be in two sub-states: Heating or Idle. This is a real example of a hierarchical state machine where states contain sub-states.

🎯 Goal: Create a hierarchical state machine in Embedded C that models the heating device states and prints the current state and sub-state.

📋 What You'll Learn

Define an enum for main states: Off and On

Define an enum for sub-states: Heating and Idle

Create variables to hold the current main state and sub-state

Write a function to print the current main state and sub-state

💡 Why This Matters

🌍 Real World

Hierarchical state machines are used in embedded systems like home appliances, robots, and automotive controls to manage complex behaviors clearly and efficiently.

💼 Career

Understanding hierarchical state machines is essential for embedded software engineers working on real-time systems and device firmware.

1

Define main states enum and current state variable

Create an enum called MainState with values OFF and ON. Then create a variable called currentMainState of type MainState and set it to OFF.

Embedded C

// Your code here

Need a hint?

Use typedef enum { OFF, ON } MainState; to define the main states.

2

Define sub-states enum and current sub-state variable

Create an enum called SubState with values HEATING and IDLE. Then create a variable called currentSubState of type SubState and set it to IDLE.

Embedded C

typedef enum {
    OFF,
    ON
} MainState;

MainState currentMainState = OFF;

// Your code here

Need a hint?

Define sub-states similarly to main states using typedef enum.

3

Write a function to print current states

Write a function called printCurrentState that prints the current main state and sub-state using printf. Use switch statements on currentMainState and currentSubState to print the state names as strings.

Embedded C

typedef enum {
    OFF,
    ON
} MainState;

MainState currentMainState = OFF;

typedef enum {
    HEATING,
    IDLE
} SubState;

SubState currentSubState = IDLE;

// Your code here

Need a hint?

Use nested switch statements to print main and sub-states.

4

Print the current state in main

Write a main function that calls printCurrentState() to display the current states.

Embedded C

typedef enum {
    OFF,
    ON
} MainState;

MainState currentMainState = OFF;

typedef enum {
    HEATING,
    IDLE
} SubState;

SubState currentSubState = IDLE;

#include 

void printCurrentState() {
    printf("Main State: ");
    switch (currentMainState) {
        case OFF:
            printf("OFF\n");
            break;
        case ON:
            printf("ON\n");
            printf("Sub State: ");
            switch (currentSubState) {
                case HEATING:
                    printf("HEATING\n");
                    break;
                case IDLE:
                    printf("IDLE\n");
                    break;
            }
            break;
    }
}

// Your code here

Need a hint?

Call printCurrentState() inside main() and return 0.