Configuring pin as input or output in Embedded C - Try It Yourself

Configuring Pin as Input or Output

📖 Scenario: You are working on a simple embedded system where you need to control an LED and read a button state. To do this, you must configure a microcontroller pin as either input or output.

🎯 Goal: Learn how to configure a microcontroller pin as input or output using C code.

📋 What You'll Learn

Create a variable representing the pin configuration register

Define a constant for the pin number

Write code to set the pin as output

Write code to set the pin as input

Print the pin configuration register value

💡 Why This Matters

🌍 Real World

Microcontrollers use pin configuration registers to control hardware pins for sensors, LEDs, buttons, and communication.

💼 Career

Embedded software engineers must know how to configure pins correctly to interface with hardware devices.

1

Create pin configuration register and pin number

Create an unsigned int variable called PIN_CONFIG and set it to 0. Then create a constant int called PIN_NUMBER and set it to 3.

Embedded C

unsigned int PIN_CONFIG = 0;
const int PIN_NUMBER = 3;
// Your code here

Need a hint?

Use unsigned int for the register and const int for the pin number.

2

Define output mode mask

Create a constant unsigned int called OUTPUT_MODE and set it to 1 << PIN_NUMBER.

Embedded C

unsigned int PIN_CONFIG = 0;
const int PIN_NUMBER = 3;
const unsigned int OUTPUT_MODE = 1 << PIN_NUMBER;
// Your code here

Need a hint?

Use bit shifting to create a mask for the pin.

3

Set pin as output and then as input

Set PIN_CONFIG to output mode by using PIN_CONFIG |= OUTPUT_MODE;. Then set PIN_CONFIG to input mode by using PIN_CONFIG &= ~OUTPUT_MODE;.

Embedded C

unsigned int PIN_CONFIG = 0;
const int PIN_NUMBER = 3;
const unsigned int OUTPUT_MODE = 1 << PIN_NUMBER;

// Set pin as output
// Your code here

// Set pin as input
// Your code here

Need a hint?

Use bitwise OR to set the bit and bitwise AND with NOT to clear the bit.

4

Print the final pin configuration

Use printf to print the value of PIN_CONFIG as an unsigned integer with the format "%u\n".

Embedded C

unsigned int PIN_CONFIG = 0;
const int PIN_NUMBER = 3;
const unsigned int OUTPUT_MODE = 1 << PIN_NUMBER;

PIN_CONFIG |= OUTPUT_MODE;
PIN_CONFIG &= ~OUTPUT_MODE;

// Print PIN_CONFIG
// Your code here

Need a hint?

Use printf("%u\n", PIN_CONFIG); inside main().