Serial communication doesn't work

Projects Programming
1

Hi,
With the following code I'd like to test serial communication between Python and my Arduino.

Python code:

import serial
import time

x = 0
y = 0

arduinoData = serial.Serial('COM6', 9600)
arduinoData.timeout = 1

while True:
   i = input("on/off: ").strip()
   if i == 'done':
      print('finished program')
      break
   arduinoData.write(i.encode())
   time.sleep(0.5)
   print(arduinoData.readline().decode('ascii'))

arduinoData.close()

Arduino code:

#define X_STEP_PIN         54
#define X_DIR_PIN          55
#define X_ENABLE_PIN       38
#define X_MIN_PIN           3
#define X_MAX_PIN           2

#define Y_STEP_PIN         60
#define Y_DIR_PIN          61
#define Y_ENABLE_PIN       56
#define Y_MIN_PIN          14
#define Y_MAX_PIN          15

#define Z_STEP_PIN         46
#define Z_DIR_PIN          48
#define Z_ENABLE_PIN       62
#define Z_MIN_PIN          18
#define Z_MAX_PIN          19

#define E_STEP_PIN         26
#define E_DIR_PIN          28
#define E_ENABLE_PIN       24

#define Q_STEP_PIN         36
#define Q_DIR_PIN          34
#define Q_ENABLE_PIN       30

#define SDPOWER            -1
#define SDSS               53
#define LED_PIN            13

#define FAN_PIN            9

#define PS_ON_PIN          12
#define KILL_PIN           -1

#define HEATER_0_PIN       10
#define HEATER_1_PIN       8
#define TEMP_0_PIN          13   // ANALOG NUMBERING
#define TEMP_1_PIN          14   // ANALOG NUMBERING

String serialData;

void setup() {


  
  pinMode(FAN_PIN , OUTPUT);
  pinMode(HEATER_0_PIN , OUTPUT);
  pinMode(HEATER_1_PIN , OUTPUT);
  pinMode(LED_PIN  , OUTPUT);
 
  pinMode(X_STEP_PIN  , OUTPUT);
  pinMode(X_DIR_PIN    , OUTPUT);
  pinMode(X_ENABLE_PIN    , OUTPUT);
 
  pinMode(Y_STEP_PIN  , OUTPUT);
  pinMode(Y_DIR_PIN    , OUTPUT);
  pinMode(Y_ENABLE_PIN    , OUTPUT);
 
  pinMode(Z_STEP_PIN  , OUTPUT);
  pinMode(Z_DIR_PIN    , OUTPUT);
  pinMode(Z_ENABLE_PIN    , OUTPUT);
 
  pinMode(E_STEP_PIN  , OUTPUT);
  pinMode(E_DIR_PIN    , OUTPUT);
  pinMode(E_ENABLE_PIN    , OUTPUT);
 
  pinMode(Q_STEP_PIN  , OUTPUT);
  pinMode(Q_DIR_PIN    , OUTPUT);
  pinMode(Q_ENABLE_PIN    , OUTPUT);
 
   digitalWrite(X_ENABLE_PIN    , LOW);
   digitalWrite(Y_ENABLE_PIN    , LOW);
   digitalWrite(Z_ENABLE_PIN    , LOW);
   digitalWrite(E_ENABLE_PIN    , LOW);
   digitalWrite(Q_ENABLE_PIN    , LOW);

     Serial.begin(9600);
}

void loop () {
  if (Serial.available() > 0){
    serialData = Serial.readStringUntil('\n');
  }

  if (serialData == "on"){
  if (millis() %1000 <500)
    digitalWrite(LED_PIN, HIGH);
  else
    digitalWrite(LED_PIN, LOW);
 
  if (millis() %1000 <300) {
    digitalWrite(HEATER_0_PIN, HIGH);
    digitalWrite(HEATER_1_PIN, LOW);
    digitalWrite(FAN_PIN, LOW);
  } else if (millis() %1000 <600) {
    digitalWrite(HEATER_0_PIN, LOW);
    digitalWrite(HEATER_1_PIN, HIGH);
    digitalWrite(FAN_PIN, LOW);
  } else  {
    digitalWrite(HEATER_0_PIN, LOW);
    digitalWrite(HEATER_1_PIN, LOW);
    digitalWrite(FAN_PIN, HIGH);
  }
 
  if (millis() %10000 <5000) {
    digitalWrite(X_DIR_PIN    , HIGH);
    digitalWrite(Y_DIR_PIN    , HIGH);
    digitalWrite(Z_DIR_PIN    , HIGH);
    digitalWrite(E_DIR_PIN    , HIGH);
    digitalWrite(Q_DIR_PIN    , HIGH);
  }
  else {
    digitalWrite(X_DIR_PIN    , LOW);
    digitalWrite(Y_DIR_PIN    , LOW);
    digitalWrite(Z_DIR_PIN    , LOW);
    digitalWrite(E_DIR_PIN    , LOW);
    digitalWrite(Q_DIR_PIN    , LOW);
  }
 
  digitalWrite(X_STEP_PIN    , HIGH);
  digitalWrite(Y_STEP_PIN    , HIGH);
  digitalWrite(Z_STEP_PIN    , HIGH);
  digitalWrite(E_STEP_PIN    , HIGH);
  digitalWrite(Q_STEP_PIN    , HIGH);
  delay(1);
 
  digitalWrite(X_STEP_PIN    , LOW);
  digitalWrite(Y_STEP_PIN    , LOW);
  digitalWrite(Z_STEP_PIN    , LOW);
  digitalWrite(E_STEP_PIN    , LOW);
  digitalWrite(Q_STEP_PIN    , LOW); 
  } 
}

The Arduino program itself works pretty well. But as soon as I add the code for serial communication, the Arduino no longer executes my commands.

I thank you in advance for any support!

2

Every time that an external device opens the Serial port of most Arduinos the board resets. Could that be a problem ?

3

Get communication working with small test programs and make sure you understand it, before implementing in the target system.

4

This Simple Python - Arduino demo may help. The Python code should work on Windows if you edit it to use the Windows style of COM ports.

...R