Firmware for Curio

An Arduino Mega 2560 rosserial_arduino client for controlling a Sawppy rover. To be used in conjunction with the curio packages.

Overview

The firmware implements an instance of a rosserial_client that runs on the Arduino and is managed by a rosserial node running on the rover's onboard computer.

The firmware provides:

• A base controller to control the rover's servos
• A decoder for a radio control receiver

Both functions can be enabled or disabled by compile time switches, and the radio control decoder can be configured to process either pulse width modulated signals or a radio control serial communication protocol called SUMD.

Dependencies

• rosserial_python - manages the host-side of the serial connection and communication to other ROS nodes.
• rosserial_arduino - provides the client Arduino ROS interface: publish and subscribe messages, access parameters, etc.
• curio_msgs - define the message format used for controlling servos and publishing radio control PWM data.
• EnableInterrupt - used by the PWM decoder to handle interrupts for each of the RC channels.

Installation

Here we describe how to build and install the firmware to your Arduino. In the following SKETCHBOOK_PATH is the path to your Arduino sketchbook directory.

Clone the repository into your catkin workspace, then build:

cd ~/curio_ws/src
git clone https://github.com/srmainwaring/curio_firmware.git
cd ~/curio_ws
catkin build

Build and install the ROS libraries for the Arduino:

cd ~/curio_ws
rosrun rosserial_arduino make_libraries.py .
cp -rp ./ros_lib SKETCHBOOK_PATH/libraries

Add a file ros_dummy.h to the ROS Arduino library in SKETCHBOOK_PATH/libraries/ros_lib/ containing the following:

// ros_dummy.h
// A placeholder so that the Arduino IDE can find header files
// in subdirectories of ros_lib when re-declaring ros.h 
// in your project
//
// In your copy of ros.h include this file. 
//
// Resources:
//  http://wiki.ros.org/rosserial_arduino/Tutorials/NodeHandle%20and%20ArduinoHardware
//  https://www.codeproject.com/Articles/1279552/Rodney-A-Long-Time-Coming-Autonomous-Robot-Part-7

#ifndef _ROS_LIB_ROS_DUMMY_H_
#define _ROS_LIB_ROS_DUMMY_H_

namespace ros {
}

#endif // _ROS_LIB_ROS_DUMMY_H_

(My thanks to Phil Hopley's excellent blog for his explanation of why this is is needed).

Copy the firmware source to the sketchbook folder:

cp -rp `rospack find curio_firmware`/firmware/curio_firmware SKETCHBOOK_PATH/curio_firmware

From the Arduino IDE open the sketch and adjust configuration settings described in the section below as required. Finally compile the sketch and download it to your Arduino.

Configuration

The main sketch file curio_firmware.ion contains the following configuration flags:

ENABLE_ARDUINO_LX16A_DRIVER

• 1: Enable the Arduino LX-16A driver. The Arduino will subscribe to servo commands and publish unfiltered servo positions.
• 0: Disable the Arduino LX-16A driver. All servo control is carried out by the Python base controller.

Note that the corresponding flag in curio_base/src/base_controller.py must also be set.

ENABLE_RADIO_CONTROL_DECODER

• 1: Enable the radio control decoder. The Arduino will publish radio control PWM values on a curio_msgs/Channels message.
• 0: Disable the radio control decoder.

ENABLE_RADIO_CONTROL_SUMD

• 1: Use the SUMD decoder.
• 0: Use the PWM decoder.

Hardware

The following wiring instructions apply to the Arduino Mega 2560.

Lewansoul BusLinker

• 5V on the BusLinker to Arduino +5V
• GND on the BusLinker to Arduino GND
• TX on the BusLinker to Arduino RX1 PIN 19
• RX on the BusLinker to Arduino TX1 PIN 18

Radio control receiver

SUMD

• + on the receiver to Arduino +5V
• - on the receiver to Arduino GND
• S channel 5 on the receiver to Arduino RX2 PIN 17

PWM

• + on the receiver to Arduino +5V
• - on the receiver to Arduino GND
• S channel 1 on the receiver to Arduino PIN 2
• S channel 2 on the receiver to Arduino PIN 3
• S channel 3 on the receiver to Arduino PIN 4
• S channel 4 on the receiver to Arduino PIN 5
• S channel 5 on the receiver to Arduino PIN 6
• S channel 6 on the receiver to Arduino PIN 7

Usage

See the documentation for curio.

ROS

The parameters, publications and subscriptions supported are affected by the configuration settings. For instance if radio control is disabled the curio_msgs::Channels messages will not be published.

Parameters

• ~wheel_servo_ids : list
  A list of integer wheel servo ids, has (default [11, 12, 13, 21, 22, 23])
• ~steer_servo_ids : list
  A list of integer steering servo ids, has (default [111, 131, 211, 231])
• ~steer_servo_angle_offsets : list
  A list of integer steering servo angle offsets for adjusting steering trim, has (default [0, 0, 0, 0]

Publications

• servo/positions : curio_msgs/CurioServoPositions
  The wheel and steering servo positions (rate 30Hz)
• servo/states : curio_msgs/CurioServoStates
  The diagnostic state of each servo (rate 1Hz)
• radio/channels : curio_msgs/Channels
  PWM values for one or more radio control channels

Subscriptions

• servo/commands : curio_msgs/CurioServoCommands
  The commanded duty and position for the wheel and steering servos

License

This software is licensed under the BSD-3-Clause license found in the LICENSE file in the root directory of this source tree.