RPi.GPIO library setup in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this GPIO setup code?

Consider this Python code snippet using the RPi.GPIO library. What will be printed when this code runs?

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)
print(GPIO.gpio_function(18))

A 0

B 1

C 2

D 3

💡 Hint

GPIO.gpio_function(pin) returns a number representing the pin mode. GPIO.OUT corresponds to 1.

The code sets pin 18 as an output pin using BCM numbering. The gpio_function returns 1 for output mode.

❓ Predict Output

intermediate

What error does this GPIO setup code raise?

What error will this code produce when run on a Raspberry Pi?

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(22, "OUT")

A RuntimeError

B TypeError

C ValueError

D No error

💡 Hint

The setup function expects a constant like GPIO.OUT, not a string.

The GPIO.setup function requires the mode argument to be a constant like GPIO.OUT, not a string. Passing "OUT" causes a ValueError.

🔧 Debug

advanced

Why does this GPIO output not toggle as expected?

This code is intended to toggle GPIO pin 17 on and off once. Why does it not work as expected?

Raspberry Pi

import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
GPIO.output(17, GPIO.HIGH)
GPIO.output(17, GPIO.LOW)
GPIO.cleanup()

A GPIO.output requires a boolean True/False, not GPIO.HIGH/LOW.

B GPIO.cleanup() resets the pin before setting LOW, so the LOW command fails.

C GPIO.setmode(GPIO.BCM) must be called after setup, not before.

D The pin is set HIGH and immediately set LOW without delay, so the change is too fast to observe.

💡 Hint

Think about how fast the commands run and what you can actually see.

The code sets the pin HIGH and then immediately LOW without any pause. The change happens too quickly to notice. Adding a delay between the two commands would make the toggle visible.

🧠 Conceptual

advanced

What is the difference between GPIO.BCM and GPIO.BOARD modes?

When setting up GPIO pins, what is the key difference between using GPIO.setmode(GPIO.BCM) and GPIO.setmode(GPIO.BOARD)?

A GPIO.BCM is for input pins only; GPIO.BOARD is for output pins only.

B GPIO.BCM uses Broadcom chip numbering; GPIO.BOARD uses physical pin numbering on the header.

C GPIO.BCM requires root access; GPIO.BOARD does not.

D GPIO.BCM disables pull-up resistors; GPIO.BOARD enables them by default.

💡 Hint

Think about how pins are identified on the Raspberry Pi.

GPIO.BCM mode refers to the Broadcom chip's GPIO numbering, while GPIO.BOARD mode refers to the physical pin numbers on the Raspberry Pi's header.

🚀 Application

expert

How many pins are set as outputs after this code runs?

Given this code, how many GPIO pins are configured as outputs at the end?

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
pins = [5, 6, 13, 19]
for pin in pins:
    GPIO.setup(pin, GPIO.OUT)
GPIO.setup(6, GPIO.IN)
GPIO.setup(19, GPIO.IN)

A 2

B 4

C 3

D 1

💡 Hint

Consider the effect of the last two setup calls on pins 6 and 19.

Initially, pins 5, 6, 13, and 19 are set as outputs. Then pins 6 and 19 are reconfigured as inputs. So only pins 5 and 13 remain outputs.