pyserial library usage in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this pyserial code snippet?

Consider this Python code using pyserial to open a serial port and read data:

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
data = ser.readline()
print(data)

Assuming the device sends the bytes b'Hello\n', what will be printed?

Raspberry Pi

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
data = ser.readline()
print(data)

A b'Hello\n'

B 'Hello\n'

C Hello

D b'Hello'

💡 Hint

Remember that readline() returns bytes, not a string.

The readline() method returns a bytes object including the newline character. So the output is b'Hello\n'.

🧠 Conceptual

intermediate

Which parameter sets the baud rate in pyserial?

In the serial.Serial() constructor, which parameter controls the communication speed (baud rate)?

A baudrate

B port

C timeout

D parity

💡 Hint

Think about the term that defines bits per second.

The baudrate parameter sets the speed of communication in bits per second.

❓ Predict Output

advanced

What error does this pyserial code raise?

What error will this code raise?

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

Raspberry Pi

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

A No error, writes successfully

B ValueError: invalid port

C AttributeError: 'Serial' object has no attribute 'write'

D TypeError: a bytes-like object is required, not 'str'

💡 Hint

Check the type of data write() expects.

The write() method requires bytes, not a string. Passing a string causes a TypeError.

📝 Syntax

advanced

Which option correctly opens a serial port with a 2-second timeout?

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

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

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

C serial.Serial('/dev/ttyS0', baudrate=115200, timeout=2.0)

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

💡 Hint

Check parameter names and types carefully.

Option B uses correct parameter names and types. Option B passes timeout as string, which is invalid. Option B is valid syntax but timeout as float is accepted, but the question expects integer 2. Option B uses wrong parameter name baud.

🚀 Application

expert

How to flush input buffer before reading data?

You want to clear any old data in the input buffer before reading fresh data from the serial port. Which method should you call?

A ser.flushInput()

B ser.clear()

C ser.reset_input_buffer()

D ser.flush()

💡 Hint

Look for the modern method name to reset input buffer.

The reset_input_buffer() method clears the input buffer. flushInput() is deprecated. flush() flushes output buffer. clear() does not exist.