mcp3008_adc

ROS2 Jazzy driver for MCP3008 10-bit 8-channel ADC over SPI (Microchip).

The MCP3008 is one of the most popular ADCs for Raspberry Pi projects. It provides 8 single-ended analog input channels via SPI, making it easy to read analog sensors (potentiometers, thermistors, photoresistors, etc.) with a Raspberry Pi that has no built-in ADC.

Features

• Publishes std_msgs/Float32 per active channel on adc/channel{0-7}
• fake_mode for testing without hardware (random Gaussian data)
• 8 single-ended channels, 10-bit resolution (1024 steps)
• SPI interface (no I2C address conflicts)
• Configurable reference voltage and SPI speed
• Voltage offset calibration via service call
• Runtime publish_rate change via ros2 param set

Prerequisites

• ROS 2 Jazzy
• Python 3
• spidev (pip install spidev) — only needed for real hardware
• SPI enabled on Raspberry Pi (sudo raspi-config)

Installation

cd ~/ros2_ws
colcon build --packages-select mcp3008_adc --symlink-install
source install/setup.bash

Usage

Launch (default: fake_mode)

ros2 launch mcp3008_adc mcp3008_launch.py

Direct execution

ros2 run mcp3008_adc mcp3008_node.py --ros-args -p fake_mode:=true

Real hardware (Raspberry Pi)

ros2 launch mcp3008_adc mcp3008_launch.py params_file:=my_params.yaml

YAML override

mcp3008_adc_node:
  ros__parameters:
    fake_mode: false
    spi_bus: 0
    spi_device: 0
    vref: 3.3
    active_channels: [0, 1, 2, 3]

Topic echo

ros2 topic echo /adc/channel0

Parameters

Parameter	Type	Default	Description
fake_mode	bool	true	Use fake driver (no hardware)
spi_bus	int	0	SPI bus number (0 or 1)
spi_device	int	0	CE pin (0=CE0, 1=CE1)
spi_speed	int	1000000	SPI clock speed (Hz)
vref	double	3.3	Reference voltage (Volts)
publish_rate	double	10.0	Publishing rate (Hz)
active_channels	int[]	[0..7]	Channels to read (0–7)

Services

Service	Type	Description
adc/calibrate	std_srvs/srv/Trigger	Collect samples for 2s, compute voltage offset bias
adc/reset	std_srvs/srv/Trigger	Clear bias, reinitialise sensor

Package Structure

mcp3008_adc/
├── CMakeLists.txt
├── CONTRIBUTING.md
├── LICENSE
├── README.md
├── .gitignore
├── package.xml
├── config/
│   └── mcp3008_params.yaml
├── launch/
│   └── mcp3008_launch.py
├── nodes/
│   └── mcp3008_node.py
├── mcp3008_adc/
│   ├── __init__.py
│   └── mcp3008_driver.py
└── test/
    └── test_mcp3008_node.py

Test Results

Tested on Ubuntu 24.04 (WSL2) with fake_mode: true.

Test Category	Test	Result
Topics	adc/channel{0-7} publishes std_msgs/Float32	PASS
Services	adc/calibrate returns success=True	PASS
Services	adc/reset returns success=True	PASS
Parameters	publish_rate runtime change	PASS
Shutdown	Clean exit	PASS
Linting	pep257, flake8, copyright, xmllint	PASS

License

MIT