pcf8591_adc_dac

ROS2 Jazzy driver for PCF8591 8-bit 4-channel ADC + 1-channel DAC over I2C (NXP).

The PCF8591 is a popular combo ADC/DAC chip that provides 4 analog input channels and 1 analog output channel in a single I2C device. It is widely used with Raspberry Pi for reading analog sensors and generating simple analog output signals.

Features

• Publishes std_msgs/Float32 per active ADC channel on adc/channel{0-3}
• Publishes DAC feedback on dac/output (std_msgs/Float32)
• Subscribes to dac/command (std_msgs/Float32) to set DAC output
• fake_mode for testing without hardware
• 8-bit resolution (256 steps) for both ADC and DAC
• Configurable reference voltage and active channels
• Voltage offset calibration via service call
• Runtime publish_rate change via ros2 param set

Prerequisites

• ROS 2 Jazzy
• Python 3
• smbus2 (pip install smbus2) — only needed for real hardware

Installation

cd ~/ros2_ws
colcon build --packages-select pcf8591_adc_dac --symlink-install
source install/setup.bash

Usage

Launch (default: fake_mode)

ros2 launch pcf8591_adc_dac pcf8591_launch.py

Direct execution

ros2 run pcf8591_adc_dac pcf8591_node.py --ros-args -p fake_mode:=true

Set DAC output

ros2 topic pub /dac/command std_msgs/msg/Float32 "{data: 1.65}" --once

Read ADC / DAC

ros2 topic echo /adc/channel0
ros2 topic echo /dac/output

YAML override

pcf8591_node:
  ros__parameters:
    fake_mode: false
    i2c_bus: 1
    device_address: 0x48
    vref: 5.0
    active_channels: [0, 1]

Parameters

Parameter	Type	Default	Description
fake_mode	bool	true	Use fake driver (no hardware)
i2c_bus	int	1	I2C bus number
device_address	int	0x48	I2C address (0x48–0x4F)
vref	double	3.3	Reference voltage (Volts)
publish_rate	double	10.0	Publishing rate (Hz)
active_channels	int[]	[0,1,2,3]	ADC channels to read (0–3)

Services

Service	Type	Description
pcf8591/calibrate	std_srvs/srv/Trigger	Collect samples for 2s, compute ADC voltage offset bias
pcf8591/reset	std_srvs/srv/Trigger	Clear bias, reinitialise sensor

Package Structure

pcf8591_adc_dac/
├── CMakeLists.txt
├── CONTRIBUTING.md
├── LICENSE
├── README.md
├── .gitignore
├── package.xml
├── config/
│   └── pcf8591_params.yaml
├── launch/
│   └── pcf8591_launch.py
├── nodes/
│   └── pcf8591_node.py
├── pcf8591_adc_dac/
│   ├── __init__.py
│   └── pcf8591_driver.py
└── test/
    └── test_pcf8591_node.py

Test Results

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

Test Category	Test	Result
Topics	adc/channel{0-3} publishes std_msgs/Float32	PASS
Topics	dac/output publishes std_msgs/Float32	PASS
Services	pcf8591/calibrate returns success=True	PASS
Services	pcf8591/reset returns success=True	PASS
Parameters	publish_rate runtime change	PASS
Shutdown	Clean exit	PASS
Linting	pep257, flake8, copyright, xmllint	PASS

License

MIT