Raspberry Pi hardware overview (GPIO, USB, HDMI) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

GPIO Pin State Reading

What is the output of this Python code snippet that reads a GPIO pin state on a Raspberry Pi?

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP)
state = GPIO.input(18)
print(state)

A GPIO.IN

B 1

C 0

D Raises RuntimeError

💡 Hint

Consider the pull-up resistor setting and what it means for the input pin state when nothing is connected.

The pin 18 is set as input with a pull-up resistor, so if nothing is connected, the input reads as high (1).

🧠 Conceptual

intermediate

USB Port Power Limits

Which statement correctly describes the power limits of USB ports on a Raspberry Pi 4?

A All USB ports share a total current limit of 1.2A combined.

B Each USB port can supply up to 1.2A independently.

C USB ports do not supply power, only data signals.

D Each USB port can supply up to 500mA independently.

💡 Hint

Think about the total power budget for USB devices connected to the Pi.

On Raspberry Pi 4, all USB ports share a combined current limit of about 1.2A total, not per port.

❓ Predict Output

advanced

HDMI Display Resolution Detection

What will this Python code print when run on a Raspberry Pi connected to a 1920x1080 HDMI display?

Raspberry Pi

import subprocess
output = subprocess.run(['tvservice', '-s'], capture_output=True, text=True)
print(output.stdout.strip())

A Error: tvservice command not found

B state 0x40001 [LCD], 800x480 @ 60.00Hz, progressive

C state 0x12000a [HDMI DMT (82) RGB full 16:9], 1280x720 @ 60.00Hz, progressive

D state 0x12000a [HDMI CEA (16) RGB lim 16:9], 1920x1080 @ 60.00Hz, progressive

💡 Hint

Look for the resolution and refresh rate in the output string.

The tvservice command reports the current HDMI mode. For a 1920x1080 display at 60Hz, it shows the CEA mode with that resolution.

🔧 Debug

advanced

Fixing GPIO Output Code

What error does this code raise when trying to set a GPIO pin high on a Raspberry Pi?

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
GPIO.output(17, 2)

A RuntimeError: GPIO not set up

B TypeError: GPIO.output() takes 2 positional arguments but 3 were given

C ValueError: The GPIO pin value must be 0 or 1

D No error, pin set high

💡 Hint

Check the allowed values for GPIO.output() when setting pin state.

GPIO.output() expects the value to be 0 (low) or 1 (high). Passing 2 causes a ValueError.

🚀 Application

expert

Calculate Total GPIO Pins Available

How many general-purpose input/output (GPIO) pins are available on a Raspberry Pi 4 Model B for user programming?

A 26 pins

B 40 pins

C 28 pins

D 17 pins

💡 Hint

Consider the total pins on the header and which are reserved for power or ground.

The Raspberry Pi 4 has a 40-pin header, but 26 of these are GPIO pins; the rest are power and ground pins.