Serial protocol design in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Raspberry Pi serial read code?

Consider this Python code snippet running on a Raspberry Pi reading from a serial port. What will be printed?

Raspberry Pi

import serial
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
data = ser.read(5)
print(data)

A b''

B b'hello'

C hello

D None

💡 Hint

Think about what happens if no data is available on the serial port within the timeout.

The read(5) call tries to read 5 bytes but if no data arrives within 1 second timeout, it returns an empty bytes object b''.

🧠 Conceptual

intermediate

Which serial protocol feature ensures data integrity?

In serial communication protocols, which feature helps detect errors in transmitted data?

A Stop bit

B Baud rate

C Parity bit

D Start bit

💡 Hint

This feature adds an extra bit to check if data was corrupted.

The parity bit is used to detect errors by making the number of set bits even or odd.

🔧 Debug

advanced

Why does this Raspberry Pi serial write code raise an exception?

This code snippet attempts to write a string to the serial port but raises an exception. What is the cause?

Raspberry Pi

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

A No exception, code runs fine

B TypeError because write expects bytes, not str

C ValueError because baud rate is invalid

D SerialException because port is closed

💡 Hint

Check the data type expected by the write method.

The write method requires bytes, but a string was passed causing a TypeError.

📝 Syntax

advanced

Which option correctly initializes a serial port with 8 data bits, no parity, and 1 stop bit?

Choose the correct Python code to configure a serial port on Raspberry Pi with 8N1 settings.

A serial.Serial('/dev/ttyUSB0', 9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE)

B serial.Serial('/dev/ttyUSB0', 9600, bytesize=8, parity='N', stopbits=1)

C serial.Serial('/dev/ttyUSB0', 9600, data_bits=8, parity_bit='none', stop_bit=1)

D serial.Serial('/dev/ttyUSB0', 9600, bits=8, parity='none', stops=1)

💡 Hint

Use constants from the serial module for configuration.

The pyserial library uses constants like serial.EIGHTBITS, serial.PARITY_NONE, and serial.STOPBITS_ONE for these settings.

🚀 Application

expert

How many bytes will be in the buffer after this Raspberry Pi serial read sequence?

Given this code reading from a serial port, how many bytes remain unread in the input buffer after execution?

Raspberry Pi

import serial
ser = serial.Serial('/dev/ttyUSB0', 115200, timeout=0)
ser.write(b'1234567890')
data1 = ser.read(4)
data2 = ser.read(3)
remaining = ser.in_waiting
print(remaining)

A 4

B 7

C 0

D 3

💡 Hint

Count total bytes written, bytes read, then subtract.

10 bytes written, 4 read first, then 3 read next, so 10 - 7 = 3 bytes remain.