Volatile keyword and why it matters in Embedded C - Mini Project: Build & Apply

Volatile Keyword and Why It Matters

📖 Scenario: You are working on a small embedded system that reads a hardware sensor value repeatedly. The sensor value can change at any time outside the program's control.You want to make sure your program always reads the latest sensor value and does not use a cached or optimized copy.

🎯 Goal: Build a simple program that uses the volatile keyword correctly to read a sensor value that can change unexpectedly.

📋 What You'll Learn

Create a variable to hold the sensor value

Add a flag variable to control the reading loop

Use a loop to read the sensor value repeatedly

Print the sensor value in each loop iteration

💡 Why This Matters

🌍 Real World

Embedded systems often read hardware sensors or flags that change outside the program flow. Using <code>volatile</code> ensures the program reads fresh values.

💼 Career

Understanding <code>volatile</code> is essential for embedded software engineers to write reliable device drivers and firmware.

1

Create the sensor value variable

Create an int variable called sensor_value and initialize it to 0.

Embedded C

int sensor_value = 0;  // Your code here

Need a hint?

Use int sensor_value = 0; to create the variable.

2

Add a flag variable to control the loop

Add an int variable called running and set it to 1 to control the reading loop.

Embedded C

int sensor_value = 0;
int running = 1;  // Your code here

Need a hint?

Use int running = 1; to create the flag variable.

3

Use volatile keyword and loop to read sensor

Change the declaration of sensor_value to use the volatile keyword. Then write a while loop that runs while running is 1 and inside the loop, assign sensor_value to a function call read_sensor().

Embedded C

volatile int sensor_value = 0;
int running = 1;

// Your code here

Need a hint?

Use volatile int sensor_value = 0; and a while (running == 1) loop with sensor_value = read_sensor(); inside.

4

Print the sensor value inside the loop

Inside the while loop, add a printf statement to print the text "Sensor value: %d\n" with the current sensor_value.

Embedded C

volatile int sensor_value = 0;
int running = 1;

while (running == 1) {
    sensor_value = read_sensor();
    // Your code here
}

Need a hint?

Use printf("Sensor value: %d\n", sensor_value); inside the loop.

For testing, assume read_sensor() returns 42.