Why does the pyfirmata closes after a certain amount of time running?

[leo-smi]

I don't know the right time, but the loop just closes and no error.

I'm using arduino uno R3 (chinese clone CH340).

I think there's a problem with the threading or something like that...

The code:

from pyfirmata import Arduino, util
import time


Uno = Arduino('COM3')
pin3 = Uno.get_pin('d:3:p')

dt = 0.005
N = 255

while True:
    
    for i in range(1, N+1, 1):
        # print(i/100)
        pin3.write(i/N)
        time.sleep(dt)

    for i in range(N, 0, -1):
        # print(i/100)
        pin3.write(i/N)
        time.sleep(dt)