Communicating with Arduino over UART in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this UART read code snippet?

Consider this Python code running on a Raspberry Pi to read data from an Arduino over UART. What will it print?

Raspberry Pi

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
line = ser.readline().decode('utf-8').strip()
print(line)

A Prints raw bytes without decoding

B Raises a SerialException due to missing port

C Prints the first line of data sent by Arduino as a string

D Prints an empty string always

💡 Hint

Think about what readline() and decode() do.

The readline() method reads bytes until a newline. decode('utf-8') converts bytes to string. strip() removes whitespace. So it prints the first line sent by Arduino.

🧠 Conceptual

intermediate

Which UART setting is critical for successful communication?

When setting up UART communication between Raspberry Pi and Arduino, which setting must match on both devices?

A Baud rate

B GPIO pin numbering scheme

C IP address

D Operating system version

💡 Hint

Think about the speed at which data is sent.

Both devices must use the same baud rate to correctly interpret the bits sent over UART.

🔧 Debug

advanced

Why does this UART write code fail to send data?

Look at this Raspberry Pi Python code intended to send 'Hello' to Arduino over UART. Why does it not send data?

Raspberry Pi

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write('Hello')

A Serial port not opened error

B TypeError because write expects bytes, not string

C Timeout error due to missing timeout parameter

D No error, data sent successfully

💡 Hint

Check the type of argument write() expects.

The write() method requires a bytes object, but 'Hello' is a string. It raises a TypeError.

📝 Syntax

advanced

Which option correctly opens UART port with timeout?

Choose the correct Python code to open UART port /dev/ttyS0 at 115200 baud with a 2-second timeout.

A serial.Serial('/dev/ttyS0', 115200, time_out=2)

B serial.Serial('/dev/ttyS0', baudrate=115200 timeout=2)

C serial.Serial(port='/dev/ttyS0', 115200, timeout=2)

D serial.Serial('/dev/ttyS0', 115200, timeout=2)

💡 Hint

Check the correct keyword argument spelling and commas.

Option D uses correct syntax with positional baud rate and keyword timeout. Others have syntax errors or wrong argument names.

🚀 Application

expert

How many bytes are sent by this UART write sequence?

Given this Python code on Raspberry Pi sending data to Arduino, how many bytes are sent over UART?

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600)
data = b'Pi\nArduino\n'
ser.write(data)

A 13 bytes

B 12 bytes

C 11 bytes

D 14 bytes

💡 Hint

Count all characters including escape sequences.

The byte string b'Pi\nArduino\n' contains 'P'(1), 'i'(2), '\n'(3-4), 'A'(5), 'r'(6), 'd'(7), 'u'(8), 'i'(9), 'n'(10), 'o'(11), '\n'(12-13). The \n escape sequence represents a newline character (one byte each), not literal backslash and 'n'. Total 13 bytes.