I am trying to construct a wireless mesh network through 3pi+ robots and Wixel modules. It works perfectly for just 2 robots, and somewhat unstably, but also basically works with 3 robots. However, when I try to use 4 robots with almost exactly the same code, the network becomes too unstable, making it practically impossible to operate them. I’ve tried many times with different combinations of robots, different batteries, different channels, and different baud rates. I cannot figure out why it works perfectly with 2 robots, works reasonably well for 3 robots, but becomes drastically worse for 4 or more robots. Is there any solution for this type of problem?
Code that I used:
from pololu_3pi_2040_robot import robot
from pololu_3pi_2040_robot.extras import editions
from machine import UART, Pin
import time
# Set robot ID (1, 2, or 3)
ROBOT_ID = 1 # Change this for each robot
# Determine the next robot's ID
if ROBOT_ID == 1:
NEXT_ROBOT_ID = 2
elif ROBOT_ID == 2:
NEXT_ROBOT_ID = 3
elif ROBOT_ID == 3:
NEXT_ROBOT_ID = 1
display = robot.Display()
motors = robot.Motors()
yellow_led = robot.YellowLED()
edition = editions.select()
if edition == "Standard":
max_speed = 1500
elif edition == "Turtle":
max_speed = 3000
elif edition == "Hyper":
max_speed = 1125
motors.flip_left(True)
motors.flip_right(True)
def initialize_uart():
uart = UART(0, baudrate=9600, tx=Pin(28), rx=Pin(29))
return uart
def send_command(uart, target_id, command):
packet = bytes([target_id, command])
uart.write(packet)
def read_command(uart, buffer):
while uart.any():
byte = uart.read(1)
if byte:
buffer.append(byte[0])
while len(buffer) >= 2:
target_id = buffer[0]
cmd = buffer[1]
del buffer[:2]
if target_id == ROBOT_ID:
return cmd
return None
uart = initialize_uart()
buffer = [] # Use list for buffer
display.fill(0)
display.show()
time.sleep(1)
cmd1 = 0x00 # Move forward command
cmd2 = 0x01 # Move backward command
# Robot 1 starts the cycle
if ROBOT_ID == 1:
time.sleep(1)
# Move forward
yellow_led.on()
motors.set_speeds(max_speed, max_speed)
time.sleep(1)
motors.set_speeds(0, 0)
time.sleep(1)
# Send backward command to next robot
send_command(uart, NEXT_ROBOT_ID, cmd2)
while True:
command = read_command(uart, buffer)
if command == cmd1:
# Move forward
yellow_led.on()
motors.set_speeds(max_speed, max_speed)
time.sleep(1)
motors.set_speeds(0, 0)
time.sleep(1)
# Send backward command to next robot
send_command(uart, NEXT_ROBOT_ID, cmd2)
elif command == cmd2:
# Move backward
yellow_led.off()
motors.set_speeds(-max_speed, -max_speed)
time.sleep(1)
motors.set_speeds(0, 0)
time.sleep(1)
# Send forward command to next robot
send_command(uart, NEXT_ROBOT_ID, cmd1)
This is the MicroPython code that I used for the robots, changing just the ‘ROBOT_ID’ parts in accordance with the number of robots.