State transition table approach in Embedded C - Mini Project: Build & Apply

State Transition Table Approach in Embedded C

📖 Scenario: You are programming a simple traffic light controller for an intersection. The traffic light changes states in a fixed order: Green → Yellow → Red → Green again. You want to use a state transition table to manage these changes clearly and simply.

🎯 Goal: Build a small embedded C program that uses a state transition table to move through traffic light states and print the current state.

📋 What You'll Learn

Create an enum for traffic light states

Create a state transition table as an array

Write a function to get the next state from the table

Print the current state in the main loop

💡 Why This Matters

🌍 Real World

State machines like this are used in embedded systems to control devices with clear, predictable behavior such as traffic lights, elevators, and appliances.

💼 Career

Understanding state transition tables helps in designing reliable embedded software and firmware, a key skill for embedded systems engineers.

1

Define traffic light states

Create an enum called State with these exact values: GREEN, YELLOW, and RED.

Embedded C

# Your code here

Need a hint?

Use typedef enum { ... } State; to define the states.

2

Create the state transition table

Create an array called state_transition of type State with 3 elements. The order should be: YELLOW after GREEN, RED after YELLOW, and GREEN after RED.

Embedded C

typedef enum {
    GREEN,
    YELLOW,
    RED
} State;

# Your code here

Need a hint?

The array state_transition holds the next state for each current state.

3

Write a function to get the next state

Write a function called get_next_state that takes a State current and returns the next state using the state_transition array.

Embedded C

typedef enum {
    GREEN,
    YELLOW,
    RED
} State;

State state_transition[3] = {YELLOW, RED, GREEN};

// Your code here

Need a hint?

Use the current state as an index to get the next state from the array.

4

Print the traffic light states in a loop

In main, create a variable current_state initialized to GREEN. Use a for loop to print the current state name 6 times, updating current_state each time by calling get_next_state. Use printf to print the state names exactly as: "GREEN", "YELLOW", or "RED".

Embedded C

typedef enum {
    GREEN,
    YELLOW,
    RED
} State;

State state_transition[3] = {YELLOW, RED, GREEN};

State get_next_state(State current) {
    return state_transition[current];
}

int main() {
    // Your code here
}

Need a hint?

Use a switch to print the state names and update the state each loop.