I2C bus architecture (SDA, SCL) in Embedded C - Mini Project: Build & Apply

I2C Bus Architecture: Understanding SDA and SCL Lines

📖 Scenario: You are working on a small embedded system that communicates with a sensor using the I2C bus. The I2C bus uses two lines: SDA (data line) and SCL (clock line). Your task is to simulate the basic setup and operation of these lines in code.

🎯 Goal: Build a simple embedded C program that sets up the SDA and SCL lines as variables, configures a clock speed, simulates sending data bits over the SDA line synchronized with the SCL clock, and finally prints the transmitted data bits.

📋 What You'll Learn

Create variables representing the SDA and SCL lines

Set a clock speed variable for the SCL line

Simulate sending a byte of data bit by bit over SDA synchronized with SCL

Print the transmitted bits to show the data sent

💡 Why This Matters

🌍 Real World

I2C is a common communication protocol used in embedded systems to connect sensors, displays, and other devices using just two wires.

💼 Career

Understanding how to manipulate and simulate I2C signals in code is useful for embedded software engineers working on hardware communication and device drivers.

1

Setup SDA and SCL lines

Create two integer variables called SDA and SCL and initialize both to 1 to represent idle high lines.

Embedded C

int SDA = 1;
int SCL = 1;
// Your code here

Need a hint?

In I2C, both SDA and SCL lines are high when idle. Use int variables to represent these lines.

2

Configure SCL clock speed

Create an integer variable called clock_speed_khz and set it to 100 to represent 100 kHz clock speed for the SCL line.

Embedded C

int SDA = 1;
int SCL = 1;
int clock_speed_khz = 100;
// Your code here

Need a hint?

The SCL clock speed is often set in kilohertz. Use an integer variable to store this value.

3

Simulate sending data bits over SDA synchronized with SCL

Create a character array data with the value {0xA5}. Then write a for loop using int i from 7 down to 0 to extract each bit from data[0]. Inside the loop, set SDA to the current bit value (0 or 1) using bitwise operations.

Embedded C

int SDA = 1;
int SCL = 1;
int clock_speed_khz = 100;
char data[1] = {0xA5};
for (int i = 7; i >= 0; i--) {
    // Your code here
}

Need a hint?

Use bit shifting and bitwise AND to get each bit from the byte. Loop from the most significant bit (7) down to 0.

4

Print transmitted bits

Inside the for loop, add a printf statement to print the current SDA bit value without a newline. After the loop, print a newline character.

Embedded C

int SDA = 1;
int SCL = 1;
int clock_speed_khz = 100;
char data[1] = {0xA5};
for (int i = 7; i >= 0; i--) {
    SDA = (data[0] >> i) & 1;
    // Your code here
}
// Your code here

Need a hint?

Use printf("%d", SDA); inside the loop to print bits continuously, then print a newline after the loop.