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Only released in EOL distros:   electric fuerte groovy

Overview

The Serializer package consists of a Python driver and ROS node for the Serializer microcontroller made by the Robotics Connection. The Serializer connects to a PC or SBC using either a USB port or XBEE radios.

Serializer Node

serializer-node.py

A ROS node for the Serializer microcontroller made by the Robotics Connection.

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.

~sensors (serializer/SensorState)

• An array of sensor names and values.

Services

~SetServo (serializer/SetServo)

• Set the target position of servo on pin 'id' to 'value'.

~GetAnalog (serializer/GetAnalog)

• Get the value from an analog sensor on pin 'id'.

~Voltage (serializer/Voltage)

• Return the voltage on the Serializer's main terminals.

~Ping (serializer/Ping)

• Query a Ping sonar sensor on digital pin 'id'.

~GP2D12 (serializer/GP2D12)

• Query a GP2D12 IR sensor on analog pin 'id'.

~PhidgetsTemperature (serializer/PhidgetsTemperature)

• Query a Phidgets Temperature sensor on analog pin 'id'.

~PhidgetsVoltage (serializer/PhidgetsVoltage)

• Query a Phidgets voltage sensor on analog pin 'id'.

~PhidgetsCurrent (serializer/PhidgetsCurrent)

• Query a Phidgets current sensor on analog pin 'id'.

~Rotate (serializer/Rotate)

• Rotate the robot base through 'angle' radians at 'velocity' rad/s.

~TravelDistance (serializer/TravelDistance)

• Move the robot forward or backward through 'distance' meters at 'velocity' m/s.

Parameters

~port (str, default: /dev/ttyUSB0)

• Serial port.

~baud (int, default: 19200)

• Baud rate.

~timeout (float, default: 0.5)

• Timeout for serial port in seconds.

~publish_sensors (bool, default: False)

• Whether or not to automatically publish sensor data.

~sensor_rate (int, default: 10)

• Rate to poll sensors and publish data.

~use_base_controller (bool, default: False)

• Whether or not to use the PID base controller.

~units (int, default: 0)

• Measurement units to use: 0 = metric, 1 = English, 2 = raw. For use with ROS, it is recommended to always leave this set to 0 for metric.

~wheel_diameter (float, default: none)

• Wheel diameter in meters.

~wheel_track (float, default: none)

• Wheel track in meters.

~encoder_type (int, default: 1)

• Encoder type: 0 = single, 1 = quadrature

~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.

~init_pid (bool, default: False)

• Whether or not to write the PID parameters to the Serializer firmware.

~VPID_P (int, default: none)

• Velocity Proportial PID parameter.

~VPID_I (int, default: none)

• Velocity Integral PID parameter.

~VPID_D (int, default: none)

• Velocity Derivative PID parameter.

~VPID_L (int, default: none)

• Velocity Loop PID parameter.

~DPID_P (int, default: none)

• Distance Proportial PID parameter.

~DPID_I (int, default: none)

• Distance Integral PID parameter.

~DPID_D (int, default: none)

• Distance Derivative PID parameter.

~DPID_L (int, default: none)

• Distance Loop PID parameter.

~base_controller_rate (int, default: 10)

• Rate to publish odometry information.

Provided tf Transforms

odom → base_link

• Transform needed for navigation.

Configuration

The recommended way to configure the Serializer node is to use a YAML file specifying the required parameters. A sample parameter file called sample_params.yaml is included in the distribution and is shown below. Note that many of the parameters are commented out and must be set and un-commented before you can use the node with your Serialzier:

port: /dev/ttyUSB0
baud: 19200
timeout: 1
sensor_rate: 10
#use_base_controller: True
#base_controller_rate: 10
#wheel_diameter: <fill in and uncomment for your robot>
#wheel_track: <fill in and uncomment for your robot>
#encoder_type: 1
#encoder_resolution: <fill in and uncomment for your robot>
#gear_reduction: <fill in and uncomment for your robot>
#motors_reversed: False
#init_pid: True
#units: 0
#VPID_P: <fill in and uncomment for your robot>
#VPID_I: <fill in and uncomment for your robot>
#VPID_D: <fill in and uncomment for your robot>
#VPID_L: <fill in and uncomment for your robot>
#DPID_P: <fill in and uncomment for your robot>
#DPID_I: <fill in and uncomment for your robot>
#DPID_D: <fill in and uncomment for your robot>
#DPID_A: <fill in and uncomment for your robot>
#DPID_B: <fill in and uncomment for your robot>

publish_sensors: True

# Examples only - change accordingly for your robot.
analog: { voltage: {pin: 5, type: Voltage}, drive_current: {pin: 1, type: PhidgetsCurrent}, light_sensor: {pin: 2, type: Analog} }
#digital: { base_sonar: {pin: 5, type: Ping} }

Example Launch File

<launch>
   <node name="serializer" pkg="serializer" type="serializer_node.py" output="screen">
   <rosparam file="$(find my_robot)/params/serializer_params.yaml" command="load" />
   </node>
</launch>

Usage Notes

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

  rosparam delete /serializer

• Try to keep the sensor and PID polling rates relatively low. Something around 10Hz seems ideal although you can try 15-20Hz. Higher rates can cause the Serializer to act sporadically.
• Most of the Serializer functions have been implemented though a few have not been tested since I don't currently have some of the supported sensors. The functions that have NOT been tested are:
  • step (used with a bipolar stepper motor)
  • sweep (also used with a bipolar stepper motor)
  • srf04, srf08 and srf10 (used with a Devantech SRF04, SRF08 and SRF10 sonar sensors)
  • tpa81 (used with the Devantech TPA81 thermopile sensor)

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

• Documentation for the Python Serializer library can be found at http://www.pirobot.org/code/serializer.html

• The official Serializer manual can be found at http://www.roboticsconnection.com/multimedia/docs/Serializer_3.0_UserGuide.pdf