Arduino ROS - arieldo/MorBot GitHub Wiki

Enriching Your Robot's Interaction: A ROS and Arduino Integration

In the realm of robotics, the synergy between software frameworks like ROS and hardware platforms such as Arduino offers boundless possibilities. From simple sensors to complex modules, this integration unlocks a plethora of capabilities. By bridging the gap between high-level computational power and low-level hardware interfacing, we can achieve more nuanced robot behaviors and adaptability. This tutorial delves into one such integration—combining the power of ROS with the simplicity of Arduino to enhance a Jetbot's perception using a Sharp IR sensor. This approach can be expanded to include other sensors and devices, enabling a richer interaction between your robot and its environment. Let's embark on this journey of upgrading our robot's sensory world.

In this tutorial, we will explore how to integrate sensors connected to an Arduino with the Jetbot through ROS. Specifically, we will use an Arduino Nano and a Sharp IR distance sensor.

Table of Contents

  1. Prerequisites
  2. Setup the Arduino
  3. Setting up ROS
  4. Create a New Launch File

Create a New ROS Package for Camera publishing Node

Prerequisites

  • JetBot environment set up Jetson Nano and Linux Setup
  • ROS environment set up on your jetson , IF not Check out HowTo ROS
  • Basic knowledge of ROS concepts, such as nodes, topics, and messages ,IF not Check out ROS 101
  • Basic knowledge of Publisher and Subscriber in Python for ROS ,IF not Check out ROS PubSubPy
  • Basic knowledge of Creating new Packages in ROS
  • Basic knowledge of Python programming language
  • Arduino Nano (or any other compatible board).
  • Sharp IR distance sensor (or any other compatible sensor).
  • Basic knowledge of Arduino and ROS.

Setup the Arduino

  1. Connect the Sharp IR sensor to the analog A0 pin on your Arduino Nano.
  2. Upload the following code to your Arduino using the Arduino IDE:
#include <SharpIR.h>

#define ir A0
#define model 20150

SharpIR SharpIR(ir, model);

void setup() {
  Serial.begin(115200);
}

void loop() {
  int sensorValue = analogRead(ir);
  float voltage = sensorValue * (5.0 / 1023.0);
  float distance = 27.728 * pow(voltage, -1.2045);
  Serial.println(distance);
  delay(10);
}
  1. Connect the Arduino to your Jetson Nano using a USB cable.

Setting up ROS

  • First Installe pyserial library:
    pip3 install pyserial
  1. Create a new package named ir_sensor inside your workspace directory (~/MorBot/morbot_ros/morbot_ws/src):
    cd ~/MorBot/morbot_ros/morbot_ws/src
    catkin_create_pkg ir_sensor rospy std_msgs
  1. Create a new directory named scripts inside your package directory (~/MorBot/morbot_ros/morbot_ws/src/ir_sensor):
    cd ~/MorBot/morbot_ros/morbot_ws/src/ir_sensor
    mkdir scripts
  1. Create a new source file inside the scripts directory. For example, create a Python file named ir_sensor_publisher.py:
    cd scripts
    touch ir_sensor_publisher.py

Make the script executable:

    cd ~/MorBot/morbot_ros/morbot_ws/src/ir_sensor/scripts
    chmod +x ir_sensor_publisher.py
  1. The ir_sensor_publisher.py

This script reads the distance from the Sharp IR sensor and publishes it to the /ir_sensor ROS topic.

#!/usr/bin/env python3

import serial
import rospy
from std_msgs.msg import Float32

# Set up the serial line
ser = serial.Serial('/dev/ttyUSB0', 115200)
ser.flushInput()

# Set up ROS
rospy.init_node('sharp_ir')
pub = rospy.Publisher('sharp_ir_range', Float32, queue_size=10)
rate = rospy.Rate(100)  # 100Hz

try:
    while not rospy.is_shutdown():
        if ser.in_waiting > 0:
            try:
                distance = float(ser.readline().strip())
                msg = Float32()
                msg.data = distance
                pub.publish(msg)
            except ValueError:
                pass  # if the float conversion fails, just ignore it
        rate.sleep()
except rospy.ROSInterruptException:
    pass
finally:
    ser.close()
  1. Build the package:
    cd ~/MorBot/morbot_ros/morbot_ws
    catkin_make
    source devel/setup.bash
  1. Run the node:
  • Open new terminal windows and run :
    roscore
  • Open new terminal windows and run :
    sudo chmod 777 /dev/ttyUSB0
    rosrun ir_sensor ir_sensor_publisher.py
  • Open new terminal windows and run :
    rostopic echo /sharp_ir_range

Create a New Launch File

  1. Create a new directory named launch inside your package directory (~/MorBot/morbot_ros/morbot_ws/src/ir_sensor):
    cd ~/MorBot/morbot_ros/morbot_ws/src/ir_sensor   
    mkdir launch
  1. Create a new launch file inside the launch directory. For example, create a launch file named ir_sensor.launch:
    cd launch
    touch ir_sensor.launch
  1. Edit the launch file to include the following:
<launch>
    <node  name="ir_sensor_publisher" pkg="ir_sensor" type="ir_sensor_publisher.py" output="screen" />
</launch>
  1. Run the launch file:
    roslaunch ir_sensor ir_sensor.launch
  1. Check the published distance:
    rostopic echo /sharp_ir_range

Now, your Arduino Nano with the Sharp IR sensor should be communicating with the Jetbot through ROS. The sensor's readings are published on the sharp_ir_range topic.

In this tutorial, we covered the integration of a Sharp IR sensor connected to an Arduino Nano with a Jetbot using ROS. This approach can be expanded to include other sensors and devices, enabling a richer interaction between your robot and its environment.

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