Arduino Serial programming issue

Question

I'm sending an integer from python using pySerial.

import serial
ser = serial.Serial('/dev/cu.usbmodem1421', 9600);
ser.write(b'5');

When i compile,the receiver LED on arduino blinks.However I want to cross check if the integer is received by arduino. I cannot use Serial.println() because the port is busy. I cannot run serial monitor first on arduino and then run the python script because the port is busy. How can i achieve this?

Answer 1

You can upload an arduino program that listens for that specific integer and only blinks the light if it gets that int.

Answer 2

You could listen for the Arduino's reply with some additional code.

import serial
ser = serial.Serial('/dev/cu.usbmodem1421', 9600); # timeout after a second

while ser.isOpen():
    try:
        ser.write(b'5');
        while not ser.inWaiting():  # wait till something's received
            pass
        print(str(ser.read(), encoding='ascii'))  #decode and print
    except KeyboardInterrupt:  # close the port with ctrl+c
        ser.close()

Use Serial.print() to print what the Arduino receives to the serial port, where your Python code is also listening.