Python Serial Port Programming Tutorial for Beginners using PySerial Module

RSDevX
3 min readJun 24, 2022

Tutorial on connecting an Arduino with a Windows PC using serial port (VCP). and communicating with it using Python and PySerial library.

pySerial Module

pySerial is an easy to use opensource elibrary that simplifies the access to the SerialPort using Python.

The Library is cross platform and can be used on Linux, Windows, Mac and BSD

you can use the PIP installer to install pySerial on your Python installation.

or by giving the below command

. python -m pip install pyserial

PC Arduino Serial Communication Block Diagram

PC Arduino Serial Communication using Python and Pyserial

PC and Arduino are connected as shown above using a single USB cable.

A more detailed explanation of how to connect the Arduino/Atmega328P with Pc can be found here

Writing data to Serial Port using Python and pySerial

Python serial port transmission tutorial

The below code transmits a byte A to the Arduino and Arduino and Arduino blinks a LED.

# Python code transmits a byte to Arduino /Microcontroller

import serial

import time

SerialObj = serial.Serial(‘COM24’) # COMxx format on Windows
# ttyUSBx format on Linux

SerialObj.baudrate = 9600 # set Baud rate to 9600
SerialObj.bytesize = 8 # Number of data bits = 8
SerialObj.parity =’N’ # No parity
SerialObj.stopbits = 1 # Number of Stop bits = 1

time.sleep(3)

SerialObj.write(b’A’) #transmit ‘A’ (8bit) to micro/Arduino

SerialObj.close() # Close the port

The first line import serial imports the pySerial module so that your programcan use it.
ComPort = serial.Serial(‘COM24’) opens the serial port named COM24.

Serial communication occurs in bytes (8 bits) while Python3+ handles strings in unicode format which may consume upto 4 bytes.

In the above Example,

we are sending a byte ‘A’. Here A is defined as a byte by using b prefix. You can also use the bytearray() function.

SerialObj.write(b’A’) #transmit ‘A’ (8bit) to micro/Arduino

Reading Data from Serial port using Python and Pyserial

Python serial port reception tutorial using pyserial

PySerial provides two functions to read data from the serial port

  • readline()
  • read()

readline() reads till it encounters a newline character ‘\n’ and returns the bytes it has read.

If \n character is not encountered it will wait forever or until the read timeout expires.

Partial Python Code (PC side)

ReceivedString = SerialObj.readline()
print(ReceivedString)
SerialObj.close()

The Arduino sends a string which is received by the PC side Python code and displayed on terminal.

PC receiving data from arduino using serial communication in Python

Arduino Side Code

USB to Serial Converter

In the above tutorial we learned how to connect an Arduino board with a PC and communicate with it (Receive/Transmit data ) using a standard USB cable.

What if instead of an Arduino we just want to connect a bare microcontroller like ATmega328P,ATmega16,MSP430 or PIC18F4550 to your PC.

When you are using a microcontroller which do not have any built in USB controller like ATmega16 or MSP430G2553 ,you have to use a USB to Serial Converter chip like FT232RL or buy a standard USB to serial converter board like USB2SERIAL

USB to Serial,RS232,RS485 Converter (USB2SERIAL V3.0)

to convert serial signals to the USB ones.

Original Article

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