smbus2 library for I2C in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the smbus2 library.

Raspberry Pi

from smbus2 import [1]

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

ADevice

BI2C

CBus

DSMBus

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'I2C' instead of 'SMBus' as the import.

Trying to import 'Bus' which does not exist in smbus2.

The SMBus class is imported from the smbus2 library to communicate over I2C.

2fill in blank

medium

Complete the code to create an SMBus object for I2C bus number 1.

Raspberry Pi

bus = [1](1)

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

ASMBus

BI2CBus

CBus

DDevice

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'I2CBus' which is not part of smbus2.

Using 'Bus' which is undefined.

The SMBus(1) creates an object for I2C bus number 1 on Raspberry Pi.

3fill in blank

hard

Fix the error in the code to write a byte value 0x10 to device address 0x20 at register 0x01.

Raspberry Pi

bus.write_byte_data([1], 0x01, 0x10)

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

A0x10

B0x01

C0x20

D0x00

Attempts:

3 left

💡 Hint

Common Mistakes

Using the register or value as the device address.

Using 0x00 which is usually not the device address.

The first argument to write_byte_data is the device address, which is 0x20 here.

4fill in blank

hard

Fill both blanks to read a byte from register 0x05 of device address 0x30.

Raspberry Pi

data = bus.[1]([2], 0x05)

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

Aread_byte_data

B0x30

C0x20

Dwrite_byte_data

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write_byte_data' instead of 'read_byte_data'.

Using wrong device address like 0x20.

Use read_byte_data method with device address 0x30 to read from register 0x05.

5fill in blank

hard

Fill all three blanks to write a block of data [0x01, 0x02, 0x03] to register 0x10 of device address 0x40.

Raspberry Pi

bus.[1]([2], 0x10, [3])

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

Awrite_i2c_block_data

B0x40

C[0x01, 0x02, 0x03]

Dread_i2c_block_data

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'read_i2c_block_data' instead of write.

Using wrong device address or data format.

Use write_i2c_block_data with device address 0x40 and the data list to write multiple bytes to register 0x10.

Practice

1. What is the main purpose of the smbus2 library when used with a Raspberry Pi?

easy

A. To control the Raspberry Pi's GPIO pins directly

B. To connect the Raspberry Pi to Wi-Fi networks

C. To communicate with I2C devices by reading and writing data

D. To manage file storage on the Raspberry Pi

Solution

1. Step 1: Understand the role of smbus2

   The smbus2 library is designed to help the Raspberry Pi communicate with I2C devices by sending and receiving data.

2. Step 2: Compare with other options

   Options A, B, and D relate to GPIO pins, Wi-Fi networks, and file storage, which are not the functions of smbus2.

3. Final Answer:

   To communicate with I2C devices by reading and writing data -> Option C

4. Quick Check:

   smbus2 = I2C communication [OK]

Hint: Remember smbus2 is for I2C device communication only [OK]

Common Mistakes:

• Confusing smbus2 with Wi-Fi or GPIO libraries
• Thinking smbus2 manages files or storage
• Assuming smbus2 controls hardware pins directly

2. Which of the following is the correct way to open an I2C bus safely using smbus2 in Python?

easy

A. open(SMBus(1))
# use bus

B. bus = SMBus(1)
# use bus
bus.close()

C. bus = SMBus()
# use bus

D. with SMBus(1) as bus:
# use bus

Solution

1. Step 1: Identify the recommended safe usage

   The recommended way is to use a context manager: with SMBus(1) as bus: which automatically opens and closes the bus safely.

2. Step 2: Check other options for correctness

   bus = SMBus(1) # use bus bus.close() manually opens and closes but is less safe. bus = SMBus() # use bus misses the bus number. open(SMBus(1)) # use bus uses invalid syntax.

3. Final Answer:

   with SMBus(1) as bus: # use bus -> Option D

4. Quick Check:

   Use 'with' to open SMBus safely [OK]

Hint: Use 'with SMBus(bus_number) as bus:' for safe bus handling [OK]

Common Mistakes:

• Not specifying the bus number when creating SMBus
• Forgetting to close the bus after use
• Using invalid syntax like open() with SMBus

3. What will be the output of this code snippet using smbus2?

from smbus2 import SMBus
with SMBus(1) as bus:
    data = bus.read_byte_data(0x20, 0x01)
print(data)

Assuming device at address 0x20 returns 42 for register 0x01.

medium

A. 42

B. 0x20

C. Error: Device not found

D. None

Solution

1. Step 1: Understand the read_byte_data function

   The function reads a byte from the device at address 0x20, register 0x01. The problem states it returns 42.

2. Step 2: Check the print output

   The variable 'data' will hold the value 42, so printing it outputs 42.

3. Final Answer:

   42 -> Option A

4. Quick Check:

   read_byte_data returns device register value [OK]

Hint: read_byte_data returns the byte value from device register [OK]

Common Mistakes:

• Confusing device address with returned data
• Expecting hexadecimal output instead of decimal
• Assuming None or error without device connection

4. Identify the error in this code snippet using smbus2:

from smbus2 import SMBus
bus = SMBus(1)
data = bus.read_byte_data(0x50)
bus.close()

medium

A. Missing register address in read_byte_data call

B. Bus number 1 is invalid

C. SMBus class not imported correctly

D. bus.close() should be called before reading data

Solution

1. Step 1: Check read_byte_data parameters

   The method requires two arguments: device address and register address. Here only device address 0x50 is given.

2. Step 2: Verify other parts

   Bus number 1 is valid, SMBus is imported correctly, and closing after reading is correct.

3. Final Answer:

   Missing register address in read_byte_data call -> Option A

4. Quick Check:

   read_byte_data needs device and register addresses [OK]

Hint: read_byte_data needs two arguments: device and register [OK]

Common Mistakes:

• Passing only device address to read_byte_data
• Closing bus before reading data
• Using wrong bus number without checking hardware

5. You want to write the byte value 0xAB to register 0x10 of an I2C device at address 0x30 using smbus2. Which code snippet correctly does this inside a safe bus context?

hard

A. with SMBus(1) as bus:
bus.write_byte_data(0x10, 0x30, 0xAB)

B. with SMBus(1) as bus:
bus.write_byte_data(0x30, 0x10, 0xAB)

C. with SMBus(1) as bus:
bus.write_byte(0x30, 0x10, 0xAB)

D. bus = SMBus(1)
bus.write_byte(0x30, 0x10, 0xAB)
bus.close()

Solution

1. Step 1: Identify correct method and parameters

   The method to write a byte to a device register is write_byte_data(device_address, register, value). with SMBus(1) as bus: bus.write_byte_data(0x30, 0x10, 0xAB) uses this correctly.

2. Step 2: Check safe bus usage and parameter order

   with SMBus(1) as bus: bus.write_byte_data(0x30, 0x10, 0xAB) uses 'with' for safe bus handling and correct parameter order. bus = SMBus(1) bus.write_byte(0x30, 0x10, 0xAB) bus.close() uses wrong method name and manual close. with SMBus(1) as bus: bus.write_byte(0x30, 0x10, 0xAB) uses wrong method. with SMBus(1) as bus: bus.write_byte_data(0x10, 0x30, 0xAB) swaps register and device address.

3. Final Answer:

   with SMBus(1) as bus: bus.write_byte_data(0x30, 0x10, 0xAB) -> Option B

4. Quick Check:

   write_byte_data(device, register, value) inside 'with' [OK]

Hint: Use write_byte_data(device, register, value) inside 'with' block [OK]

Common Mistakes:

• Using write_byte instead of write_byte_data for register writes
• Swapping device address and register parameters
• Not using 'with' for safe bus handling