asc_node - Arduino Stepper Controller ROS Node

This firmware uses an Arduino Uno Rev. 3 as a ROS node to control a stepper motor by using a common motor driver. Communication to a client (PC) is established by using rosserial_arduino package. Rosserial provides a ROS communication protocol that works over Arduino's UART. The node runs on the Arduino independently of a client and publishes messages which can be read out over rosserial.

Hardware

• Arduino Uno Rev. 3
• DRV8825 motor driver

Why DRV8825

Adafruit motor shield is very limited due to missing current limitation and voltage restriction. DRV8825 motor driver can be used over a wider range. Node works with all generic two-pin (DIR/STEP) motor drivers.

Functions

The node accesses functions which are used to control a stepper motor.

Set up Arduino and install rosserial

http://wiki.ros.org/rosserial_arduino/Tutorials/Arduino%20IDE%20Setup

Arduino IDE

Arduino IDE is used. Project is divided into several class files. Need to install ros_lib first.

ros_lib and custom dependencies

To use custom dependencies (e.g. custom messages, services etc.), you have to build these first (catkin build) and then install ros_lib by using the following commands (and not over Arduino IDE):

rm -r ~/Arduino/libraries/ros_lib

rosrun rosserial_arduino make_libraries.py ~/Arduino/libraries

Access data from client console

roscore

rosrun rosserial_python serial_node.py /dev/ttyUSB0 (rosserial client application)

rostopic echo <topic_name>

rostopic pub <topic_name> std_msgs/Int32 --once "<value>"

List of Topics/Services

Homing:

rosservice call /stepper_homing_srv

Set position (between -44 and 50 degree, only possible after homing):

rosservice call /stepper_abs_pos_srv "target_abs_position: 0.0"

Joint state information (only position):

rostopic echo /joint_state

rosserial

http://wiki.ros.org/rosserial

http://wiki.ros.org/rosserial_arduino/Tutorials

ROS package dependencies

Only to create messages. Replace by your own:

• custom_communication

Arduino Libraries

• AccelStepper

Sources

https://www.pololu.com/product/2133

http://www.airspayce.com/mikem/arduino/AccelStepper/index.html

Attention

• Stepper doesn't stop exactly at the homing switch.
• Problems with serial connection arise if the delays are set too short.
• Buffer size and number of subscribers/publishers was limited due to low dynamic memory (in ros.h)