SPI with display modules in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this SPI initialization code?

Consider this Python code snippet for initializing SPI on a Raspberry Pi to communicate with a display module. What will be printed when this code runs?

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 500000
print(spi.max_speed_hz)

A 500000

B 0

C None

D SyntaxError

💡 Hint

Look at the value assigned to max_speed_hz and what is printed.

The code sets spi.max_speed_hz to 500000 and then prints it, so the output is 500000.

🧠 Conceptual

intermediate

Which SPI mode is commonly used for most display modules?

SPI devices use modes 0 to 3 to define clock polarity and phase. Which SPI mode is most commonly compatible with typical SPI display modules?

A Mode 2 (CPOL=1, CPHA=0)

B Mode 1 (CPOL=0, CPHA=1)

C Mode 0 (CPOL=0, CPHA=0)

D Mode 3 (CPOL=1, CPHA=1)

💡 Hint

Most SPI displays use clock polarity and phase starting with clock low and sampling on the first clock edge.

Mode 0 is the default SPI mode for many display modules, meaning clock polarity 0 and clock phase 0.

🔧 Debug

advanced

Why does this SPI display code raise an error?

This code tries to send data to an SPI display but raises an error. What is the cause?

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0)
spi.xfer2([0xAA, 0xBB])

A TypeError because open() requires two arguments: bus and device

B AttributeError because xfer2() is not a method of SpiDev

C RuntimeError because SPI device is busy

D ValueError because data list contains invalid bytes

💡 Hint

Check the parameters required by spi.open() method.

spi.open() requires two arguments: bus and device. Calling it with one argument causes a TypeError.

📝 Syntax

advanced

Which option correctly sends a command byte 0x01 followed by data bytes [0x02, 0x03] to an SPI display?

Select the correct Python code snippet using spidev to send a command byte followed by data bytes over SPI.

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

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

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

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

💡 Hint

xfer2() takes a list of bytes to send in one call.

spi.xfer2([0x01, 0x02, 0x03]) sends all bytes in one SPI transaction. Other options are invalid or incorrect method usage.

🚀 Application

expert

How many bytes are sent over SPI in this code snippet?

Given this code sending data to an SPI display, how many bytes are transmitted in total?

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
data = [0x10, 0x20, 0x30]
for byte in data:
    spi.xfer2([byte])

A 1

B 3

C 0

D 6

💡 Hint

Each call to xfer2 sends one byte in a list; the loop runs three times.

The loop sends one byte per iteration, three iterations total, so 3 bytes are sent.