Simple state machine with switch-case in Embedded C - Mini Project: Build & Apply

Simple state machine with switch-case

📖 Scenario: You are programming a simple traffic light controller for a small intersection. The traffic light cycles through three states: RED, GREEN, and YELLOW. Each state lasts for a certain number of seconds before switching to the next.

🎯 Goal: Build a simple state machine using switch-case in C to cycle through the traffic light states and print the current state.

📋 What You'll Learn

Create an enum for the traffic light states: RED, GREEN, YELLOW

Create a variable called current_state to hold the current state

Use a switch-case statement to handle state transitions

Print the current state name in each case

💡 Why This Matters

🌍 Real World

Traffic lights and many devices use state machines to control behavior based on current conditions.

💼 Career

Understanding state machines and switch-case logic is essential for embedded systems programming and device control.

1

Define the traffic light states

Create an enum called TrafficLight with the states RED, GREEN, and YELLOW. Then create a variable called current_state of type enum TrafficLight and set it to RED.

Embedded C

enum TrafficLight { RED, GREEN, YELLOW };
enum TrafficLight current_state = RED;
// Your code here

Need a hint?

Use enum TrafficLight { RED, GREEN, YELLOW }; to define the states and then enum TrafficLight current_state = RED; to set the initial state.

2

Add a variable for the timer

Create an int variable called timer and set it to 0. This will count seconds in each state.

Embedded C

enum TrafficLight { RED, GREEN, YELLOW };
enum TrafficLight current_state = RED;
int timer = 0;
// Your code here

Need a hint?

Just add int timer = 0; below the current_state variable.

3

Implement the state machine logic with switch-case

Write a switch statement on current_state. For each case (RED, GREEN, YELLOW), print the state name using printf. Then update current_state to the next state in this order: RED -> GREEN -> YELLOW -> RED.

Embedded C

enum TrafficLight { RED, GREEN, YELLOW };
enum TrafficLight current_state = RED;
int timer = 0;

switch (current_state) {
    // Your code here
}

Need a hint?

Use switch (current_state) and inside each case, print the state name and update current_state to the next state.

4

Print the current state

Add a printf statement after the switch-case block to print the text "Current state updated.".

Embedded C

enum TrafficLight { RED, GREEN, YELLOW };
enum TrafficLight current_state = RED;
int timer = 0;

switch (current_state) {
    case RED:
        printf("RED\n");
        current_state = GREEN;
        break;
    case GREEN:
        printf("GREEN\n");
        current_state = YELLOW;
        break;
    case YELLOW:
        printf("YELLOW\n");
        current_state = RED;
        break;
}

// Your code here

Need a hint?

Use printf("Current state updated.\n"); after the switch-case block.