Learn Ubiquity Robots and ROS

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Diagnostics

Sanity Checks

• When magni is on, the wheels should have strong resistance to movement.

• The command sudo systemctl status magni-baseshould show that the magni-base service is up and running

• The command rosnode list should show motor_node and other nodes. The command rostopic list should show many ROS topics, including /battery and /cmd_vel.

• After the command rosrun teleop_twist_keyboard teleop_twist_keyboard.py, pressing the ‘i’ key should move the robot.

• To change the robot’s hostname (a must if you will ever have a second robot), see the instructions in Connecting the Robot. Instructions for joining your local area network are in the same place.

• To check the battery level type: rostopic echo /battery

  This should show you various information about the battery. If the battery voltage is somewhere between 21-28V that would be normal. Obviously the lower the voltage the less charge the batteries have.

Handy Tips for Developers

• The important configuration file base.yaml is found at: /opt/ros/kinetic/share/magni_bringup/param/base.yaml. N.B. This file may be rewritten when the base is upgraded, as by apt=get.

• To disable magni startup: sudo systemctl disable magni-base and reboot so magni-base will be inactive.

  To get back to normal behavior you will need later a sudo systemctl enable magni-base and then a reboot.

• To find the firmware version: when the robot is idle,
  rosrun ubiquity_motor probe_robot -f
  For even more fun try -a instead of -f.

  If the robot is running a program, run
  sudo systemctl disable magni-base.service
  and then reboot before trying the probe_robot command again.

  To return the robot to normal startup you will then need to use sudo systemctl enable magni-base.service and reboot again.

  To find the version number of the most important ubiquity software, type:

  dpkg-query --showformat='${Package}\t${Version}\n' --show ros-kinetic-magni-robot ros-kinetic-ubiquity-motor ros-kinetic-fiducials ros-kinetic-raspicam-node ros-kinetic-pi-sonar

• To run magni services after a ‘systemctl disable’ line as shown above: roslaunch magni_bringup base.launch.

• The launch file used by the magni-base.service is /opt/ros/kinetic/share/magni_bringup/launch/base.launch.
  This launch file does rosrun controller_manager spawner ubiquity_velocity_controller ubiquity_joint_publisher.
  This invokes the ROS controller_manager; for more detail see wiki.ros.org/controller_manager.

• Much magni software will be found in /opt/ros/kinetic/share/magni_*` In particular, magni_demos/launch has ROS launch files.

Motor Controller Board Pinouts

The pinouts for the many connectors on the main Motor Controller Board can be found HERE.

Motor Controller Revisions

A list of firmware and master controller board revisions can be found HERE.

Guidelines for Usage Of The I2C Bus

The I2C devices Ubiquity Robotics reserves:

Addresses given in 7-bit form so on the I2C bus they appear shifted up by 1 bit.

• MCP7940 RTC 0x6F Realtime clock for Linux when no NTP can be contacted
• PCF8574 IO Expander 0x20 IO Expander for Ubiquity Robotics U3 on 5.x MCB.
• PCF8574A IO Expander 0x38. We have had this loaded by accident for U3
• SSD1306 OLED Disp 0x3C 8 line by 15 character small display on rev 5.x boards

Tips and Guidelines For any I2C usage On the Magni Platform:

The I2C is the main 3.3V Raspberry Pi I2C on pins 3 and 5 with Raspberry Pi as the master. The Rev 5.0 board has a 4-pin jack that brings out I2C and 3.3V with a ground.

• Use the I2C ONLY from within a ROS node to avoid conflict on the I2C bus.
• Keep the I2C lines to your device under 60mm from board to your device
• Only use devices for short data accesses and space out your accesses by at least 50msec
• If you stop Magni with sudo systemctl stop magni-base.service you can scan the I2C bus for all devices using sudo i2cdetect -y 1 if i2c-tools was installed using apt-get. The i2c-tools package also has i2cget and i2cset so look them up if curious.