SBC interface with uROS library

2022-08-18

In this tutorial we will learn how to use the uROS library for micropython: https://github.com/mgtm98/uRos

ROS is an Operating System for Robots in which the different “nodes” communicate with a central server through TCP messages in JSON format.

This library allows us to implement a ROS node in our SBC. It will connect to a server and will be able to send (publish) or receive (subscribe to) messages.

The code to post a message is as follows:

import network
from uros import *
from uros.std_msgs import std_Bool
lan = network.LAN()
lan.active(True)
lan.ifconfig( ( "10.0.0.1", "255.255.255.0", "10.0.0.2", "8.8.8.8" ) )
while( lan.status() != 3 ):
    print( ".", end="" )
    time.sleep(1)
print( "Connected!" )
uRos = Ros( "10.0.0.2", 9090 )    #creating new uRos object
msg = std_Bool( data = True )     #creating a Ros string msg object
uRos.publish( "uRosTopic", msg )  #publishing the msg object
print("done")

In this code we first connect to the LAN network and then to the ROS server; we define the format of our message and finally we publish.

On the PC we execute a code in python that acts as a ROS server. For simplicity, this code is just a socket server that prints the data to the console.

import socket
import sys
def socket_server( host, port ):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((host, port))
    s.listen(1)
    while True:
        conn, addr = s.accept()
        print('Connected by', addr)
        while True:
            data = conn.recv(1024)
            if not data:
                break
            print(data)
        conn.close()
        print("conn closed")
    s.close()
    print("s closed")
socket_server( '10.0.0.2', 9090 )
print("done")