MCP3008 ADC over SPI in Raspberry Pi - Mini Project: Build & Apply

Reading Analog Sensor Values with MCP3008 ADC over SPI on Raspberry Pi

📖 Scenario: You have a Raspberry Pi connected to an MCP3008 analog-to-digital converter (ADC) via SPI. You want to read the analog value from a sensor connected to channel 0 of the MCP3008 and display the digital value.

🎯 Goal: Build a Python program that reads the analog input from channel 0 of the MCP3008 ADC using SPI communication and prints the digital value.

📋 What You'll Learn

Create a SPI connection using the spidev library

Set up the MCP3008 channel to read (channel 0)

Send the correct SPI command to read from channel 0

Parse the response to get the 10-bit ADC value

Print the ADC value

💡 Why This Matters

🌍 Real World

Reading analog sensors like temperature, light, or potentiometers with a Raspberry Pi requires an ADC like MCP3008 because the Pi has no built-in analog inputs.

💼 Career

Understanding SPI communication and ADC reading is important for embedded systems, IoT projects, and hardware interfacing roles.

1

Set up SPI connection

Import the spidev library and create a SPI object called spi. Open SPI bus 0, device 0 using spi.open(0, 0). Set the SPI max speed to 1 MHz with spi.max_speed_hz = 1000000.

Raspberry Pi

# Import spidev and create SPI object
# Your code here

Hint

Use import spidev to access SPI functions. Create SPI object with spidev.SpiDev(). Open bus 0, device 0 with spi.open(0, 0). Set speed with spi.max_speed_hz.

2

Prepare SPI command to read channel 0

Create a list called adc_command with three bytes to read from channel 0 of MCP3008. The first byte is 1 (start bit), the second byte is 0b10000000 (single-ended mode, channel 0), and the third byte is 0.

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 1000000

# Create adc_command list to read channel 0
# Your code here

Hint

The MCP3008 expects 3 bytes: start bit (1), single-ended + channel bits (0b10000000 for channel 0), and a dummy byte (0).

3

Send SPI command and parse ADC value

Use spi.xfer2(adc_command) to send the command and receive a list called adc_response. Extract the 10-bit ADC value from adc_response by combining bits: mask the second byte with 3 (to get the last two bits), shift left 8 bits, then OR with the third byte. Store the result in a variable called adc_value.

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 1000000

adc_command = [1, 0b10000000, 0]

# Send adc_command and get adc_response
# Extract 10-bit adc_value from adc_response
# Your code here

Hint

Use spi.xfer2() to send and receive SPI data. The 10-bit value is in the last two bytes: mask the second byte with 3, shift left 8 bits, then OR with the third byte.

4

Print the ADC value

Print the variable adc_value to display the digital reading from the MCP3008.

Raspberry Pi

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 1000000

adc_command = [1, 0b10000000, 0]

adc_response = spi.xfer2(adc_command)
adc_value = ((adc_response[1] & 3) << 8) | adc_response[2]

# Print adc_value
# Your code here

Hint

Use print(adc_value) to show the ADC reading. The actual number depends on your sensor input.