Enabling SPI on Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of checking SPI status after enabling it?

After enabling SPI on Raspberry Pi using raspi-config, you run the command ls /dev/spi*. What output do you expect?

Raspberry Pi

ls /dev/spidev*

A No such file or directory

B /dev/spi0 /dev/spi1

C /dev/spidev0.0 /dev/spidev0.1

D /dev/spi_master0

💡 Hint

SPI devices appear as spidev nodes under /dev after enabling.

When SPI is enabled on Raspberry Pi, device files like /dev/spidev0.0 and /dev/spidev0.1 are created. These represent SPI bus 0 with chip selects 0 and 1.

🧠 Conceptual

intermediate

Which file must be edited to enable SPI manually on Raspberry Pi?

To enable SPI without using raspi-config, which file do you edit to load the SPI kernel module on boot?

A /etc/modules

B /boot/config.txt

C /etc/spi.conf

D /boot/cmdline.txt

💡 Hint

This file lists kernel modules to load at startup.

The /etc/modules file lists kernel modules to load during boot. Adding 'spi-bcm2835' here enables SPI manually.

🔧 Debug

advanced

Why does SPI communication fail after enabling SPI?

You enabled SPI on Raspberry Pi but your Python SPI code raises FileNotFoundError: [Errno 2] No such file or directory: '/dev/spidev0.0'. What is the most likely cause?

Raspberry Pi

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

A SPI clock speed is set too high

B Python spidev library is not installed

C SPI pins are used by another device

D SPI interface is not enabled in raspi-config or device tree

💡 Hint

The device file /dev/spidev0.0 must exist for spidev to open it.

If SPI is not enabled in raspi-config or device tree, the device files /dev/spidev* do not exist, causing FileNotFoundError.

📝 Syntax

advanced

Which command correctly enables SPI via device tree overlay?

To enable SPI by editing /boot/config.txt, which line is correct?

A dtoverlay=spi0-2cs

B dtoverlay=spi0-1cs

C dtoverlay=spi-bcm2835

D dtoverlay=spi1-1cs

💡 Hint

The overlay name specifies SPI bus and chip selects.

The overlay 'spi0-2cs' enables SPI bus 0 with 2 chip selects, which is the common default for Raspberry Pi SPI.

🚀 Application

expert

How to verify SPI communication speed in Python on Raspberry Pi?

You want to set and verify the SPI clock speed in your Python code using spidev. Which code snippet correctly sets the speed to 1 MHz and prints it?

A

spi.clock_hz = 1000000
print(spi.clock_hz)

B

spi.max_speed_hz = 1000000
print(spi.max_speed_hz)

C

spi.speed = 1_000_000
print(spi.speed)

D

spi.set_speed(1000000)
print(spi.get_speed())

💡 Hint

spidev uses max_speed_hz attribute to set clock speed.

The spidev library uses the attribute max_speed_hz to set and get SPI clock speed. Methods like set_speed or attributes like speed do not exist.