NOT for inverting bits in Embedded C - Mini Project: Build & Apply

Using NOT Operator to Invert Bits in Embedded C

📖 Scenario: You are working on a small embedded system that controls an LED display. The display uses an 8-bit register where each bit represents an LED: 1 means the LED is ON, and 0 means the LED is OFF.You want to create a program that can invert the current LED states using the NOT operator, so all ON LEDs turn OFF and all OFF LEDs turn ON.

🎯 Goal: Build a simple embedded C program that uses the NOT operator ~ to invert the bits of an 8-bit variable representing LED states.

📋 What You'll Learn

Create an 8-bit unsigned integer variable called led_state with a specific initial value.

Create a mask variable called mask to limit the bits to 8 bits.

Use the NOT operator ~ to invert the bits of led_state and apply the mask.

Print the original and inverted LED states in binary format.

💡 Why This Matters

🌍 Real World

In embedded systems, controlling hardware like LEDs often requires manipulating bits directly. Using the NOT operator to invert bits is a common task to toggle states quickly.

💼 Career

Understanding bitwise operations and how to invert bits is essential for embedded software developers working with microcontrollers, hardware registers, and low-level device control.

1

Create the initial LED state variable

Create an 8-bit unsigned integer variable called led_state and set it to 0b10101010 to represent the initial LED states.

Embedded C

# Create the variable led_state with value 0b10101010
// Your code here

Need a hint?

Use uint8_t to create an 8-bit unsigned integer and assign the binary value 0b10101010.

2

Create a mask to limit bits to 8 bits

Create an 8-bit unsigned integer variable called mask and set it to 0xFF to mask the bits after inversion.

Embedded C

#include 
#include 

uint8_t led_state = 0b10101010;

// Create the mask variable with value 0xFF
// Your code here

Need a hint?

The mask 0xFF keeps only the lowest 8 bits after inversion.

3

Invert the bits of led_state using NOT operator

Create an 8-bit unsigned integer variable called inverted_led_state and set it to the bitwise NOT of led_state masked with mask using ~led_state & mask.

Embedded C

#include 
#include 

uint8_t led_state = 0b10101010;
uint8_t mask = 0xFF;

// Invert led_state bits and apply mask
// Your code here

Need a hint?

Use the bitwise NOT operator ~ on led_state and then apply the mask with & mask.

4

Print the original and inverted LED states in binary

Write two printf statements to print led_state and inverted_led_state in 8-bit binary format using a loop to show each bit.

Embedded C

#include 
#include 

uint8_t led_state = 0b10101010;
uint8_t mask = 0xFF;
uint8_t inverted_led_state = ~led_state & mask;

int main() {
    // Print led_state in binary
    // Your code here

    // Print inverted_led_state in binary
    // Your code here
    return 0;
}

Need a hint?

Use a for loop from 7 down to 0 and print each bit by shifting and masking with 1.