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Raspberry Pi + ROS
- 1. ROS and the Raspberry Pi http://www.robopgmr.com/?page_id=3589 Arnold Bailey +ROS
- 2. Contents • The complexity of robotics • What is ROS? • Hardware and software options • Creating an ROS user application. • Conclusion 2
- 3. 3 Can complex robotic systems be programmed on an RPi? ?
- 5. • Manage diverse asynchronous activity • Manage significant complexity. • Device abstract • Multi-language operation. • Distribution of resources 5 Advanced robotic systems require:
- 6. 6 The Challenge! Need to develop expertise Cost Functionality Industry Academic Open Source
- 7. 7 • A software framework for developing robotic systems in a meta-operating system environment. • The primary goal of ROS is to support code reuse in robotics research and development • ROS was originally developed in 2007 at the Stanford Artificial Intelligence Laboratory and development continued at Willow Garage • Managed by the Open Source Robotics Foundation What is ROS?
- 9. 9 ROS Master Enables ROS nodes to locate one another and provide parameter services.
- 11. • Master(roscore): Provides naming and registration services to the rest of the nodes in the system. • Package: A virtual directory holding one or more executables (nodes) • Messages: Defined in msg files. Basic data types. • Node: An agent communicating with ROS and other nodes via messages. • Topics (publish / subscribe) using typed messages • Services: Request / Response, synchronism functionality, remote computation. • Bag: Bags are a format for recording and playback of messages. ROS Core Concepts
- 12. Arduino Uno Pi Co-op Raspberry Pi ROS Application-ard01 ROS PyMata lib Firmata lib GPIO Motion Detector LED Hardware abstraction, low-level device control read pin 8 sensor write pin 13
- 13. 13 Multiple Languages C++ Node: Map Building Python Node: Laser Scanner Topic: “Laser Data” Subscribe Publish
- 14. ROS core Components Middleware Robot Specific Features Tools • Messaging Passing • Recording/Playback • Remote Procedure Calls • Distributed Parameters • Standard Robot Messages • Robot Geometry Library • Robot Description Language • Pre-emptable RPC • Diagnostics • Pose Estimation • Localization • Navigation • Command line tools • Integrated Tools ROS
- 17. Example Hardware • Raspberry Pi • Model B • 16 GB SD (Could use 8 GB) • Pi Co-op Board • Arduino Uno (resides on board) • Parallax Motion Detecter • Breadboard 17
- 18. 18 Pymata/ Firmata Arduino Libraries rosserial_ar duino rosserial Pi Co-op x RPi to Arduino x x RPI direct to device x Hardware/software options
- 19. Pi Co-op Add-on Board • It’s a GPIO plug-in board that houses an ATmega328p chip and female headers. • Arduino Uno bootloader to make it easy to program. • Pi communicates with the chip over UART (serial) protocol. • uses a library called pyMata to control the analog inputs and digital inputs. • Can attach power to the Pi Co-op
- 20. Pi Co-op connection to Motion Detecter
- 21. RPi and Arduino Connected Over Serial GPIO
- 22. RPi connected to LED using GPIO pins
- 23. Create a Package 23 $ source /opt/ros/indigo/setup.bash $ mkdir -p ~/catkin_ws/src $ cd ~/catkin_ws/src $ catkin_init_workspace $ cd ~/catkin_ws/ $ catkin_make $ cd ~/catkin_ws $ source /opt/ros/indigo/setup.bash $ cd ~/catkin_ws/src $ catkin_create_pkg ard01 std_msgs rospy roscpp $ rospack depends1 ard01 $ roscd ard01 $ cat package.xml # view it $ rospack depends1 rospy # view $ pico package.xml Create Workspace Craete Package
- 26. #!/usr/bin/env python # import rospy from PyMata.pymata import PyMata subscriber = rospy.Subscriber("rb_motion_detect", String, scallback) rospy.init_node('rb_motion_detect', anonymous=True) Python Script Snippets Libraries Register node Subscribe to topic
- 27. 27 rospy.loginfo("Message is %s",data.data) DETECT = 8 # Pin 8 is the detect on/off # Configure the pins SERIAL_PORT = "/dev/ttyS0" # Create an instance of PyMata. firmata = PyMata( SERIAL_PORT, max_wait_time=5 ) setup Logging Python Script Snippets
- 28. 28 pub = rospy.Publisher('rb_blink_led', String, queue_size=10) str = "1 0" # message to reset blinking pub.publish(str) rospy.spin time.sleep(.1) firmata.close() Publish a MWSSAGE Delaying Delaying Wait until ROS caommand completes Python Script Snippets
- 29. Execution Terminal session 1 Roscore pi@raspberrypi ~ $ cd ~/catkin_ws pi@raspberrypi ~/catkin_ws $ source ./devel/setup.bash pi@raspberrypi ~/catkin_ws $ roscore ... logging to /home/pi/.ros/log/c4b68850-6434-11e4-a4b6-b827eb6d59e5/roslaunch- raspberrypi-2639.log pi@raspberrypi ~/catkin_ws $ rosrun ard01 rb_motion_test.py Enter start/stop/exit motion detection:start [INFO] [WallTime: 1415119214.484039] motion_detect mode requested -start Enter start/stop/exit motion detection: blepi@raspberrypi ~/catkin_ws $ rosrun ard01 rb_motion_detect.py [INFO] [WallTime: 1415119214.521525] Message is start Terminal session 3 rb_motion_detect ^Cpi@raspberrypi ~/catkin_ws $ rosrun ard01 rb_blink_led.py [INFO] [WallTime: 1415119236.277651] Message is 1 5 [INFO] [WallTime: 1415119236.290445] Requested blink rate is 1, 5 Opening Arduino Serial port /dev/ttyS0 Please wait while Arduino is being detected. This can take up to 5 seconds ... Board initialized in 0 seconds Total Number of Pins Detected = 20 Total Number of Analog Pins Detected = 6 PyMata close(): Calling sys.exit(0): Hope to see you soon! Terminal session 2 rb_motion_test Terminal session 3 rb_blink_led
- 30. Conclusion • ROS, on the Raspberry Pi is a very viable and easy to use approach to provide robotic system functionality at a very low cost. • Because ROS is used industrywide and in many of the leading universities, ROS and RPi should be the method of choice to teach robotics in the advanced high school and university levels. 30
- 31. Attachments • References • Sample Arduino sketch • Existing Systems vs ROS 31
- 32. References • Installing ROS Indigo on the RPi • Pi Co-OP video describes Pi Co-op • Reference Pi Co-op and Arduino Software Installation – Notes for the detailed instructions. • Installs PyMata (Python library) • Loads Firmata (protocol used by Pymata to I/F with the Arquino) 32
- 33. 33 // Sweep // by BARRAGAN <http://barraganstudio.com> // This example code is in the public domain #include <Servo.h> Servo myservo; // create servo object to control a servo // a maximum of eight servo objects can be created int pos = 0; // variable to store the servo position void setup() { myservo.attach(9); // attaches the servo on pin 9 to the servo object } void loop() { for(pos = 0; pos < 180; pos += 1) // goes from 0 degrees to 180 degrees { // in steps of 1 degree myservo.write(pos); // tell servo to go to position in variable 'pos' delay(15); // waits 15ms for the servo to reach the position } for(pos = 180; pos>=1; pos-=1) // goes from 180 degrees to 0 degrees { myservo.write(pos); // tell servo to go to position in variable 'pos' delay(15); // waits 15ms for the servo to reach the position } } Sample Arduino Code (IDE)
- 34. Existing Systems vs ROS General Purpose ROS Explicitly general purpose Exclusively for robotics programs Native language programming Language independent sequential architecture asynchronous distribyed programming IDE sofyware framework prprietary/open source opensource BSD license heavily coded ROS frameworks are very light programs nodes communication messages splintered usage industry-wide and academic usage