SPI with display modules in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the SPI library for Raspberry Pi.

Raspberry Pi

import [1]

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

Agpiozero

Bspidev

CRPi.GPIO

Dtime

Attempts:

3 left

💡 Hint

Common Mistakes

Importing gpiozero instead of spidev

Using RPi.GPIO which is for general GPIO, not SPI

The spidev library is used to control SPI devices on Raspberry Pi.

2fill in blank

medium

Complete the code to open SPI bus 0, device 0.

Raspberry Pi

spi = spidev.SpiDev()
spi.[1](0, 0)

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

Aconnect

Binit

Cstart

Dopen

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'connect' which is not a spidev method

Using 'init' which does not exist in spidev

The open method opens the SPI bus and device for communication.

3fill in blank

hard

Fix the error in the code to send data [0xAA, 0xBB] over SPI.

Raspberry Pi

data = [0xAA, 0xBB]
spi.[1](data)

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

Awritebytes

Bwrite

Csend

Dtransfer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' which is not a spidev method

Using 'transfer' which sends and receives data

The writebytes method sends a list of bytes over SPI without reading response.

4fill in blank

hard

Fill both blanks to set SPI max speed to 1 MHz and mode to 0.

Raspberry Pi

spi.max_speed_hz = [1]
spi.mode = [2]

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

A1000000

B0

C1

D500000

Attempts:

3 left

💡 Hint

Common Mistakes

Setting mode to 1 instead of 0

Using 500000 for max speed instead of 1000000

SPI max speed is set in Hz, so 1 MHz is 1000000. Mode 0 means clock polarity and phase are zero.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each byte in data to its hex string if byte is greater than 0x80.

Raspberry Pi

result = [1]: hex([2]) for [3] in data if [2] > 0x80

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

Abyte

Bb

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for key and iteration variable

Not converting byte to hex string

The dictionary comprehension uses b as key, b as value after converting to hex, and iterates with b over data.

Practice

1. What is the main purpose of using SPI with display modules on a Raspberry Pi?

easy

A. To power the display module

B. To connect the Raspberry Pi to the internet

C. To store files on the Raspberry Pi

D. To send commands and data quickly to the display

Solution

1. Step 1: Understand SPI role

   SPI is a communication protocol used to send data between devices quickly.

2. Step 2: Connect SPI to display modules

   On Raspberry Pi, SPI sends commands and data to control display modules efficiently.

3. Final Answer:

   To send commands and data quickly to the display -> Option D

4. Quick Check:

   SPI = fast data transfer to display [OK]

Hint: SPI is for fast data transfer to devices like displays [OK]

Common Mistakes:

• Confusing SPI with internet connection
• Thinking SPI stores files
• Assuming SPI powers devices

2. Which of the following is the correct way to open SPI bus 0, device 0 using the spidev library in Python?

easy

A. spi = spidev.SpiDev(); spi.open(0, 0)

B. spi = spidev.open(1, 0)

C. spi = spidev.open(0, 0)

D. spi = spidev.SpiDev.open(0, 0)

Solution

1. Step 1: Recall spidev usage

   spidev requires creating an SpiDev object first, then calling open(bus, device).

2. Step 2: Check syntax correctness

   spi = spidev.SpiDev(); spi.open(0, 0) correctly creates spi = spidev.SpiDev() then calls spi.open(0, 0).

3. Final Answer:

   spi = spidev.SpiDev(); spi.open(0, 0) -> Option A

4. Quick Check:

   spidev object then open() method [OK]

Hint: Create SpiDev object before calling open() [OK]

Common Mistakes:

• Calling spidev.open() directly without object
• Using wrong bus or device numbers
• Using incorrect method syntax

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

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
response = spi.xfer2([0xAA, 0x55])
spi.close()
print(response)

medium

A. [170, 85]

B. Depends on the connected SPI device response

C. An error because xfer2 needs a string

D. [0, 0]

Solution

1. Step 1: Understand xfer2 function

   spi.xfer2 sends bytes and returns the response bytes from the SPI device.

2. Step 2: Recognize device dependency

   The returned list depends on the connected device's response, so output varies.

3. Final Answer:

   Depends on the connected SPI device response -> Option B

4. Quick Check:

   SPI response varies by device [OK]

Hint: SPI transfer output depends on device response [OK]

Common Mistakes:

• Assuming output equals input bytes
• Thinking xfer2 requires string input
• Expecting fixed output without device

4. You wrote this code to send a command to your SPI display but it raises an AttributeError:

import spidev
spi = spidev.open(0, 0)
spi.xfer2([0x01])
spi.close()

What is the error and how to fix it?

medium

A. spidev has no open() function; create SpiDev object first

B. xfer2() requires a string, not a list

C. spi.close() should be called before xfer2()

D. Bus number 0 is invalid on Raspberry Pi

Solution

1. Step 1: Identify AttributeError cause

   spidev module does not have open() function; open() is method of SpiDev object.

2. Step 2: Correct usage of spidev

   Create spi = spidev.SpiDev() first, then call spi.open(0, 0) to fix error.

3. Final Answer:

   spidev has no open() function; create SpiDev object first -> Option A

4. Quick Check:

   Use SpiDev() object before open() [OK]

Hint: Always create SpiDev() object before open() [OK]

Common Mistakes:

• Calling spidev.open() directly
• Passing wrong data type to xfer2()
• Closing SPI before transfer

5. You want to send a command byte 0xA5 followed by data bytes [0x01, 0x02, 0x03] to an SPI display using spidev. Which code correctly sends the command first, then the data, assuming spi is already opened?

hard

A. spi.writebytes([0xA5, 0x01, 0x02, 0x03])

B. spi.xfer2([0xA5, 0x01, 0x02, 0x03])

C. spi.xfer2([0xA5]); spi.xfer2([0x01, 0x02, 0x03])

D. spi.writebytes([0xA5]); spi.writebytes([0x01, 0x02, 0x03])

Solution

1. Step 1: Understand command and data separation

   Many SPI displays require sending command and data separately to distinguish them.

2. Step 2: Check code options

   spi.xfer2([0xA5]); spi.xfer2([0x01, 0x02, 0x03]) sends command byte first, then data bytes in separate calls, matching typical display protocol.

3. Final Answer:

   spi.xfer2([0xA5]); spi.xfer2([0x01, 0x02, 0x03]) -> Option C

4. Quick Check:

   Separate command and data transfers [OK]

Hint: Send command and data in separate SPI transfers [OK]

Common Mistakes:

• Sending command and data in one transfer
• Using writebytes() which may not return response
• Not separating command from data