Communicating with Arduino over UART in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open the UART serial port on Raspberry Pi.

Raspberry Pi

import serial

ser = serial.Serial('/dev/ttyS0', [1])
print("Serial port opened")

Drag options to blanks, or click blank then click option'

A9600

B115200

C19200

D4800

Attempts:

3 left

💡 Hint

Common Mistakes

Using a baud rate that does not match the Arduino's baud rate.

Forgetting to specify the baud rate when opening the serial port.

The baud rate 9600 is the standard speed for UART communication with Arduino.

2fill in blank

medium

Complete the code to send the string 'Hello Arduino' over UART.

Raspberry Pi

message = 'Hello Arduino'
ser.write([1])
print("Message sent")

Drag options to blanks, or click blank then click option'

Amessage

Bstr(message)

Cmessage.encode()

Dbytes(message, 'utf-8')

Attempts:

3 left

💡 Hint

Common Mistakes

Sending a string directly without encoding causes an error.

Using bytes() without encoding may cause unexpected results.

We must encode the string to bytes before sending over UART.

3fill in blank

hard

Fix the error in reading a line from UART and decoding it.

Raspberry Pi

line = ser.readline()
text = line.[1]('utf-8').strip()
print(text)

Drag options to blanks, or click blank then click option'

Ato_string

Bdecode

Cdecode_utf8

Dencode

Attempts:

3 left

💡 Hint

Common Mistakes

Using encode() instead of decode() on bytes.

Using a non-existent method like decode_utf8 or to_string.

We use decode('utf-8') to convert bytes to string.

4fill in blank

hard

Fill both blanks to create a dictionary of word lengths for words longer than 3 characters.

Raspberry Pi

words = ['arduino', 'pi', 'uart', 'code']
lengths = {word: [1] for word in words if len(word) [2] 3}
print(lengths)

Drag options to blanks, or click blank then click option'

Alen(word)

B>

C>=

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using word instead of len(word) for dictionary values.

Using '>=' instead of '>' which includes words of length 3.

We use len(word) to get length and filter words with length greater than 3.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values greater than 2.

Raspberry Pi

data = {'temp': 1, 'humidity': 3, 'pressure': 5}
filtered = [1]: [2] for k, v in data.items() if v [3] 2}
print(filtered)

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using k instead of k.upper() for keys.

Using '<' or '>=' instead of '>' for filtering.

Keys are converted to uppercase with k.upper(), values are v, and filter uses '>' to select values greater than 2.

Practice

1. What is the main purpose of UART communication between Raspberry Pi and Arduino?

easy

A. To power the Arduino from the Raspberry Pi

B. To send and receive data serially between devices

C. To connect to the internet

D. To display graphics on a screen

Solution

1. Step 1: Understand UART communication

   UART is a serial communication protocol used to send and receive data between devices like Raspberry Pi and Arduino.

2. Step 2: Identify the purpose in context

   The main goal is to exchange data serially, not to power devices or connect to the internet.

3. Final Answer:

   To send and receive data serially between devices -> Option B

4. Quick Check:

   UART = Serial data exchange [OK]

Hint: UART is for serial data transfer, not power or internet [OK]

Common Mistakes:

• Confusing UART with power supply
• Thinking UART connects to the internet
• Assuming UART is for display output

2. Which Python code snippet correctly opens a UART serial connection at 9600 baud on Raspberry Pi?

easy

A. serial.connect('/dev/ttyS0', 9600)

B. serial.open('/dev/ttyS0', 9600)

C. serial.Serial('/dev/ttyS0', 9600)

D. serial.start('/dev/ttyS0', 9600)

Solution

1. Step 1: Recall Python serial library usage

   The correct method to open a serial port is using serial.Serial() with device and baud rate as arguments.

2. Step 2: Check each option's method name

   Only serial.Serial() is valid; others like open(), connect(), start() do not exist in pyserial.

3. Final Answer:

   serial.Serial('/dev/ttyS0', 9600) -> Option C

4. Quick Check:

   Use serial.Serial() to open UART [OK]

Hint: Use serial.Serial() to open UART port [OK]

Common Mistakes:

• Using non-existent methods like open() or connect()
• Forgetting to specify baud rate
• Using wrong device path

3. What will be the output of this Python code on Raspberry Pi communicating with Arduino over UART?

import serial
ser = serial.Serial('/dev/ttyS0', 9600, timeout=1)
ser.write(b'Hello Arduino')
response = ser.readline().decode().strip()
print(response)

medium

A. Prints the response string sent by Arduino

B. Prints 'Hello Arduino'

C. Prints an empty line

D. Raises a syntax error

Solution

1. Step 1: Analyze the code behavior

   The code sends 'Hello Arduino' bytes to Arduino and waits to read a line response with timeout.

2. Step 2: Understand the output

   It prints the decoded and stripped response from Arduino, not the sent message or empty line unless no response.

3. Final Answer:

   Prints the response string sent by Arduino -> Option A

4. Quick Check:

   ser.readline() reads Arduino reply [OK]

Hint: ser.readline() reads Arduino reply, not sent data [OK]

Common Mistakes:

• Confusing sent data with received data
• Expecting print to show sent bytes
• Ignoring decode and strip steps

4. Identify the error in this Python code snippet for UART communication on Raspberry Pi:

import serial
ser = serial.Serial('/dev/ttyS0', 115200)
ser.write('Hello')
response = ser.readline()
print(response)

medium

A. Using readline() instead of read()

B. Incorrect baud rate 115200

C. Missing import of time module

D. Using string instead of bytes in ser.write()

Solution

1. Step 1: Check ser.write() argument type

   ser.write() requires bytes, but 'Hello' is a string, causing a TypeError.

2. Step 2: Verify other parts

   Baud rate 115200 is valid, time module is not needed here, and readline() is appropriate for line reading.

3. Final Answer:

   Using string instead of bytes in ser.write() -> Option D

4. Quick Check:

   ser.write() needs bytes, not string [OK]

Hint: Always send bytes with ser.write(b'...') [OK]

Common Mistakes:

• Passing string instead of bytes to ser.write()
• Assuming baud rate is wrong without checking
• Confusing readline() with read()

5. You want to send sensor data from Arduino to Raspberry Pi over UART and store it in a Python dictionary with keys as sensor names and values as readings. Which approach is best?

hard

A. Send data as JSON string; use json.loads() in Python

B. Send raw bytes without format; decode directly to dict

C. Send data as separate lines without keys; assign manually in Python

D. Send data as 'temp:25,hum:40' string; parse in Python with split and dict comprehension

Solution

1. Step 1: Consider data format for easy parsing

   JSON format is standard, easy to parse with json.loads() into Python dict directly.

2. Step 2: Evaluate other options

   Custom string formats require manual parsing and are error-prone; raw bytes lack structure; separate lines without keys make mapping difficult.

3. Final Answer:

   Send data as JSON string; use json.loads() in Python -> Option A

4. Quick Check:

   JSON format simplifies UART data parsing [OK]

Hint: Use JSON strings for structured UART data exchange [OK]

Common Mistakes:

• Sending unstructured raw bytes
• Parsing custom formats manually
• Omitting keys in data lines