About | Support | Discussion Forum | Index | Service Status | ros @ Robotics Stack Exchange

Only released in EOL distros:   electric fuerte groovy hydro indigo

Overview

This package consists of a Python driver and ROS node for Arduino-compatible controllers. The Arduino must be connected to a PC or SBC using either a USB port or an RF serial link (e.g. XBee).

Features

• Direct support for the following sensors:
  • Ping sonar
  • Sharp infrared (GP2D12)
  • Onboard Pololu motor controller current
  • Phidgets Voltage sensor
  • Phidgets Current sensor (DC, 20A)
• Can also read data from generic analog and digital sensors
• Can control digital outputs (e.g. turn a switch or LED on and off)
• Support for PWM servos
• Configurable base controller if using the required hardware.

Arduino Node

arduino-node.py

A ROS node for Arduino-compatible microcontrollers. Sensors can be polled at independent rates (see sample config file at the end of this page.) For example, main voltage could be polled at 1 Hz while a sonar sensor could be polled at 20 Hz.

Subscribed Topics

/cmd_vel (geometry_msgs/Twist)

• Movement commands for the base controller.

Published Topics

/odom (nav_msgs/Odometry)

• Odometry messages from the base controller.

~sensor_state (ros_arduino_msgs/SensorState)

• An array of sensor names and values.

~sensor/name (sensor_msgs/Range,)

• Each sensor value is published on its own topic under the "sensor" namespace with the appropriate type. See sample config file below for examples.

Services

~servo_write (ros_arduino_msgs/ServoWrite)

• Set the target position of a servo with index 'id' to 'value' (in radians). The 'id' to pin mapping is made in the Arduino firmware.

~servo_read (ros_arduino_msgs/ServoRead)

• Get the last set position (in radians) from the servo with index 'id'.

~digital_set_direction (ros_arduino_msgs/DigitalSetDirection)

• Sets a digital pin to INPUT (0) or OUTPUT (1)

~digital_write (ros_arduino_msgs/DigitalWrite)

• Sets a digital pin either LOW (0) or HIGH (1)

Parameters

~port (str, default: /dev/ttyUSB0 -- some controllers use /dev/ttyACM0)

• Serial port.

~baud (int, default: 57600)

• Baud rate for the serial connection.

~timeout (float, default: 0.1)

• Timeout for serial port in seconds.

~rate (int, default: 50)

• Rate to run the main control loop. Should be at least as fast as the faster sensor rate.

~sensorstate_rate (int, default: 10)

• Rate to publish the overall sensor array. Note that individual sensors are published on their own topics and at their own rate.

~use_base_controller (bool, default: False)

• Whether or not to use the base controller.

~base_controller_rate (int, default: 10)

• Rate to publish odometry data.

~base_frame (New in Hydro) (string, default: base_link)

• Link to use as the base link when publishing odometry

~wheel_diameter (float, default: none)

• Wheel diameter in meters.

~wheel_track (float, default: none)

• Wheel track in meters. (Distance between centers of drive wheels.)

~encoder_resolution (int, default: none)

• Encoder ticks per wheel revolution.

~gear_reduction (float, default: 1.0)

• External gear reduction.

~motors_reversed (bool, default: False)

• Reverse the sense of wheel rotation.

~Kp (int, default: 20)

• Proportial PID parameter.

~Kd (int, default: 12)

• Derivative PID parameter.

~Ki (int, default: 0)

• Integral PID parameter.

~Ko (int, default: 50)

• Output PID parameter.

~accel_limit (float, default: 0.1)

• Max acceleration when changing wheel speeds

~sensors (dict, default: None)

• Dictionary of sensors attached to the Arduino. (See the sample YAML config file below.)

Provided tf Transforms

odom → base_link

• Transform needed for navigation.

Configuration

The Arduino node is configured using a YAML file specifying the required parameters. A sample parameter file called arduino_params.yaml is included in the config directory and is shown below. Make a copy of this file(e.g. my_arduino_params.yaml) before editing. Note that many of the parameters are commented out and must be set and un-commented before you can use the node with your Arduino.

Current valid sensor types names (case-sensitive):

• Ping
• GP2D12
• Analog (generic)
• Digital (generic)

• PololuMotorCurrent

• PhidgetsVoltage

• PhidgetsCurrent (20 amps, DC)

port: /dev/ttyUSB0
baud: 57600
timeout: 0.1

rate: 50
sensorstate_rate: 10

use_base_controller: False
base_controller_rate: 10

# === Robot drivetrain parameters
#wheel_diameter: 0.146
#wheel_track: 0.2969
#encoder_resolution: 8384 # from Pololu for 131:1 motors
#gear_reduction: 1.0
#motors_reversed: True

# === PID parameters
#Kp: 20
#Kd: 12
#Ki: 0
#Ko: 50
#accel_limit: 1.0

# === Sensor definitions.  Examples only - edit for your robot.
#     Sensor type can be one of the follow (case sensitive!):
#         * Ping
#         * GP2D12
#         * Analog
#         * Digital
#         * PololuMotorCurrent
#         * PhidgetsVoltage
#         * PhidgetsCurrent (20 Amp, DC)

sensors: {
  #motor_current_left:   {pin: 0, type: PololuMotorCurrent, rate: 5},
  #motor_current_right:  {pin: 1, type: PololuMotorCurrent, rate: 5},
  #ir_front_center:      {pin: 2, type: GP2D12, rate: 10},
  #sonar_front_center:   {pin: 5, type: Ping, rate: 10},
  arduino_led:          {pin: 13, type: Digital, rate: 5, direction: output}
}

Example Launch File

<launch>
   <node name="arduino" pkg="ros_arduino_python" type="arduino_node.py" output="screen">
      <rosparam file="$(find ros_arduino_python)/config/my_arduino_params.yaml" command="load" />
   </node>
</launch>

Usage Notes

• Be sure to put your robot on blocks before first trying the base controller

• If you mess up your parameters in a given session, just do a:
  

  rosparam delete /arduino

• The driver requires Python 2.6.5 or higher and PySerial 2.3 or higher. It has been tested on Ubuntu Linux 10.04 (Maveric) and 11.10 (Oneric).

Report a Bug

https://github.com/hbrobotics/ros_arduino_bridge/issues