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.

Practice

1. Which Raspberry Pi hardware component allows you to connect and control electronic parts like LEDs and sensors?

easy

A. GPIO pins

B. USB ports

C. HDMI port

D. Ethernet port

Solution

1. Step 1: Understand GPIO function

   GPIO pins are designed to connect and control electronic parts such as LEDs and sensors.

2. Step 2: Compare with other ports

   USB ports connect devices like keyboards, and HDMI connects to screens, so they don't control electronics directly.

3. Final Answer:

   GPIO pins -> Option A

4. Quick Check:

   GPIO = electronic control pins [OK]

Hint: GPIO pins control electronics, USB and HDMI do not [OK]

Common Mistakes:

• Confusing USB ports with GPIO pins
• Thinking HDMI controls electronics
• Selecting Ethernet port which is for network

2. Which of the following is the correct way to describe the HDMI port on a Raspberry Pi?

easy

A. Connects to electronic sensors

B. Connects to USB devices

C. Connects to power supply

D. Connects to a display screen

Solution

1. Step 1: Identify HDMI port purpose

   The HDMI port is used to connect the Raspberry Pi to a display screen like a monitor or TV.

2. Step 2: Eliminate other options

   Electronic sensors connect via GPIO, USB devices connect to USB ports, and power supply uses a separate power connector.

3. Final Answer:

   Connects to a display screen -> Option D

4. Quick Check:

   HDMI = display connection [OK]

Hint: HDMI always connects to screens, not devices or power [OK]

Common Mistakes:

• Confusing HDMI with USB ports
• Thinking HDMI connects sensors
• Mixing power supply with HDMI

3. What will happen if you connect a keyboard to the Raspberry Pi's USB port?

medium

A. The keyboard will work and allow typing input

B. The keyboard will control GPIO pins directly

C. The keyboard will display output on the HDMI screen

D. The keyboard will charge the Raspberry Pi

Solution

1. Step 1: Understand USB port function

   USB ports connect input devices like keyboards and mice to the Raspberry Pi.

2. Step 2: Analyze keyboard behavior

   When connected, the keyboard sends typing input to the Raspberry Pi; it does not control GPIO or display output.

3. Final Answer:

   The keyboard will work and allow typing input -> Option A

4. Quick Check:

   USB port = input device connection [OK]

Hint: USB ports connect input devices like keyboards [OK]

Common Mistakes:

• Thinking keyboard controls GPIO pins
• Assuming keyboard shows output on HDMI
• Believing keyboard charges the Pi

4. You tried to connect a sensor to the Raspberry Pi but it did not work. You connected it to the USB port instead of the GPIO pins. What is the likely problem?

medium

A. The sensor needs HDMI connection to work

B. The sensor requires power from the USB port only

C. USB ports cannot directly connect sensors; use GPIO pins instead

D. The sensor must be connected to the Ethernet port

Solution

1. Step 1: Identify correct sensor connection

   Sensors connect to GPIO pins because they need direct electronic control signals.

2. Step 2: Understand USB port role

   USB ports connect devices like keyboards and storage, not sensors directly.

3. Final Answer:

   USB ports cannot directly connect sensors; use GPIO pins instead -> Option C

4. Quick Check:

   Sensors use GPIO, not USB [OK]

Hint: Sensors connect to GPIO pins, not USB ports [OK]

Common Mistakes:

• Trying to use HDMI for sensors
• Assuming USB powers sensors directly
• Confusing Ethernet port with sensor connection

5. You want to build a project that lights up an LED when you press a button connected to your Raspberry Pi. Which hardware ports will you use to connect the LED and button, and how will you see the output on a screen?

hard

A. Connect LED and button to Ethernet port; use USB for screen output

B. Connect LED and button to GPIO pins; use HDMI port for screen output

C. Connect LED and button to HDMI port; use USB for screen output

D. Connect LED and button to USB ports; use GPIO pins for screen output

Solution

1. Step 1: Identify connection for LED and button

   LEDs and buttons are electronic components controlled via GPIO pins on the Raspberry Pi.

2. Step 2: Identify how to display output

   The HDMI port connects the Raspberry Pi to a screen to show output visually.

3. Final Answer:

   Connect LED and button to GPIO pins; use HDMI port for screen output -> Option B

4. Quick Check:

   GPIO for electronics + HDMI for display [OK]

Hint: Use GPIO for electronics, HDMI for screen display [OK]

Common Mistakes:

• Connecting electronics to USB or HDMI ports
• Using USB for screen output
• Confusing Ethernet port with GPIO