I have been trying to send data to my Arduino Nano via a serial connection. The data is sent properly once I start sending data immediately after initialising. However, if there is a pause in sending data, it stops sending properly.

This is my Python code. I created it for debugging:

import serial
import time
port = 'COM6' 
baudrate = 9600

# Open the serial connection
ser = serial.Serial(port, baudrate)
time.sleep(3)
data_to_send = "hello, world~"

# Encode data as bytes (optional for some data types)
data_bytes = data_to_send.encode('utf-8')  # Encodes string to bytes
while True:
    # Send data to Arduino
    ser.write(data_bytes)
    data = ser.readline()
    print("data", data)

    print(f"Data sent: {data_to_send}")

This is the Arduino code:

#include <Servo.h>


bool newData = false;
char receivedChars[64];
void setup() {
  // Motor control pins as outputs

  Serial.begin(9600);
  delay(1000);  // Give the serial connection time to initialize
  Serial.println("READY");
}

void loop() {
  static byte ndx = 0;
  char endMarker = '~';
  char rc;

  while (Serial.available() && newData == false) {
    rc = Serial.read();
    if (rc != endMarker) {
      receivedChars[ndx] = rc;
      ndx++;
    } else {
      // receivedChars[ndx] = ''; // terminate the string
      ndx = 0;
      newData = true;
    }
  }
  Serial.println(receivedChars);
    

Now if I remove time.sleep(3) from the Python code, it keeps sending data immediately after the port has been initialised. The output looks something like this:

Data sent: hello, world~
data b'hello, worldrn'
Data sent: hello, world~
data b'hello, worldrn'
Data sent: hello, world~
data b'hello, worldrn'
Data sent: hello, world~
data b'hello, worldrn'
Data sent: hello, world~
data b'hello, worldrn'

However, when time.sleep(3) is present in the code, this is the output:

Data sent: hello, world~
data b'rn'
Data sent: hello, world~
data b'rn'
Data sent: hello, world~
data b'rn'
Data sent: hello, world~
data b'rn'

I have tried setting the timeout parameter to a large value or to None but that doesn’t help either.