I'm controlling the position of a servo with Python and an Arduino. I type in the angle in python and it sends to the Arduino which then moves the servo to that specific angle. Arduino code:

#include <Servo.h>

Servo servo;

void setup()

void loop()
    int pos = Serial.parseInt();

Python code:

import serial

port = serial.Serial('COM9' ,9600, timeout=1)

while True:
        data = input("Enter servo position: ")
        byte_data = data.encode()

Everything works fine for a while and I can control the servo, but then it suddenly gives me this error:

File "C:\Users\User\Projects\p1\venv\lib\site-packages\serial\serialwin32.py", line 317, in write
    raise SerialException("WriteFile failed ({!r})".format(ctypes.WinError()))
serial.serialutil.SerialException: WriteFile failed (PermissionError(13, 'the device does not recognize the command', None, 22))

It happens pretty randomly, and I have no idea why.

  • If you're powering the servo from the 5V, I would verify that you're not browning out the board.
    – timemage
    Jun 11 at 21:39
  • Is this a serial interface over USB? (Please add the information to your questions by editing it.) Additionally, please watch the hardware manager what it shows for the connection's hardware. Jun 13 at 6:14


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