Single LED control in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Raspberry Pi LED control code?

Consider this Python code controlling an LED connected to GPIO pin 17 on a Raspberry Pi. What will be the state of the LED after running this code?

Raspberry Pi

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)

GPIO.output(17, GPIO.HIGH)
time.sleep(1)
GPIO.output(17, GPIO.LOW)
GPIO.cleanup()

A The LED stays off the whole time.

B The LED turns on for 1 second, then turns off.

C The LED blinks continuously.

D The code raises a runtime error.

💡 Hint

GPIO.HIGH turns the LED on, GPIO.LOW turns it off.

The code sets the LED pin high (on), waits 1 second, then sets it low (off) and cleans up. So the LED lights up for 1 second only.

🧠 Conceptual

intermediate

Which GPIO mode is used in this code snippet?

In Raspberry Pi Python code, what does GPIO.setmode(GPIO.BCM) mean?

A It sets all pins to input mode.

B It uses the physical pin numbering on the board.

C It uses the Broadcom chip pin numbering scheme.

D It disables all GPIO pins.

💡 Hint

BCM refers to the chip's internal numbering.

GPIO.BCM means the code uses the Broadcom SOC channel numbers, not the physical pin numbers on the board.

🔧 Debug

advanced

What error does this code raise?

What error will this Raspberry Pi LED control code produce?

Raspberry Pi

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
GPIO.output(17, 2)
GPIO.cleanup()

A ValueError: invalid output value

B TypeError: an integer is required (got type str)

C RuntimeWarning: This channel is already in use

D No error, LED turns on.

💡 Hint

GPIO.output expects GPIO.HIGH or GPIO.LOW (0 or 1), not 2.

GPIO.output expects 0 or 1 (GPIO.LOW or GPIO.HIGH). Passing 2 causes a ValueError for invalid output value.

📝 Syntax

advanced

Which option fixes the syntax error in this code?

Fix the syntax error in this Raspberry Pi LED control code snippet:

GPIO.setup(17 GPIO.OUT)

A GPIO.setup(17, GPIO.OUT)

B GPIO.setup(17 GPIO.OUT)

C GPIO.setup(17: GPIO.OUT)

D GPIO.setup(17; GPIO.OUT)

💡 Hint

Function arguments must be separated by commas.

The correct syntax uses a comma between arguments: GPIO.setup(17, GPIO.OUT).

🚀 Application

expert

How many times does the LED blink in this code?

Given this Raspberry Pi Python code, how many times will the LED blink?

Raspberry Pi

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)

for i in range(3):
    GPIO.output(17, GPIO.HIGH)
    time.sleep(0.5)
    GPIO.output(17, GPIO.LOW)
    time.sleep(0.5)

GPIO.cleanup()

A 1 time

B 6 times

C 0 times

D 3 times

💡 Hint

Each loop cycle turns the LED on and off once.

The loop runs 3 times, each time turning the LED on then off once, so 3 blinks total.