Python com port send

How to read and write from a com port using pyserial in Python?

PySerial is a Python module that allows for serial communication between a computer and microcontroller or other device. This can be useful for interfacing with various hardware devices such as sensors, actuators, and other peripherals that require serial communication. To read and write from a COM Port using PySerial, the following methods can be used:

Method 1: Initializing the Serial Port

To read and write from a COM Port using PySerial in Python, you need to initialize the serial port first. Here are the steps to do it:

Step 1: Install PySerial

Before you can use PySerial, you need to install it. You can install it using pip:

Step 2: Import the PySerial module

To use PySerial, you need to import the module:

Step 3: Initialize the Serial Port

To initialize the serial port, you need to create an instance of the Serial class. Here is an example:

ser = serial.Serial('COM1', 9600, timeout=1)

In this example, we are initializing the serial port with the following parameters:

• COM1 : The name of the COM port. You can change it to the name of the COM port you want to use.
• 9600 : The baud rate of the serial port. You can change it to the baud rate you want to use.
• timeout=1 : The timeout value in seconds. This is the maximum amount of time to wait for data to arrive. You can change it to the timeout value you want to use.

Step 4: Read from the Serial Port

To read from the serial port, you can use the read() method. Here is an example:

In this example, we are reading 10 bytes of data from the serial port and storing it in the data variable.

Step 5: Write to the Serial Port

To write to the serial port, you can use the write() method. Here is an example:

In this example, we are writing the string «Hello, World!» to the serial port.

Step 6: Close the Serial Port

When you are done using the serial port, you should close it using the close() method. Here is an example:

In this example, we are closing the serial port.

That’s it! These are the steps to initialize the serial port and read from/write to it using PySerial in Python.

Method 2: Reading from the Serial Port

To read data from a COM port using PySerial in Python, you can follow these steps:

ser = serial.Serial('COM1', 9600, timeout=1)

Where ‘COM1’ is the port name and 9600 is the baud rate. The timeout parameter specifies the time to wait for the data to arrive.

Where 10 is the number of bytes to read. You can also use the readline() method to read a line of data.

Here is an example code that reads data from a COM port:

import serial ser = serial.Serial('COM1', 9600, timeout=1) while True: data = ser.readline().decode('utf-8').rstrip() print(data) ser.close()

This code reads a line of data from the port and prints it to the console. The decode() method is used to convert the bytes to a string, and rstrip() is used to remove any trailing whitespace.

I hope this helps you to read data from a COM port using PySerial in Python.

Method 3: Writing to the Serial Port

PySerial is a Python library used to communicate with serial ports. In this tutorial, we will discuss how to read and write from a COM port using PySerial.

Before we start, make sure you have PySerial installed. If you don’t have PySerial installed, you can install it using pip:

To write to a serial port using PySerial, you need to create a Serial object and use the write() method to send data. Here’s an example:

import serial ser = serial.Serial('COM1', 9600) # Replace 'COM1' with your serial port name and 9600 with your baud rate data = 'Hello, world!' ser.write(data.encode())

In the above example, we first create a Serial object by specifying the serial port name and baud rate. We then create a variable data that contains the message we want to send. Finally, we use the write() method to send the data. Note that we need to encode the data as bytes before sending it.

After you’re done using the serial port, it’s important to close it using the close() method. Here’s an example:

import serial ser = serial.Serial('COM1', 9600) # Replace 'COM1' with your serial port name and 9600 with your baud rate data = 'Hello, world!' ser.write(data.encode()) ser.close()

Method 4: Closing the Serial Port

Here’s how you can read and write from a COM port using PySerial in Python with the added step of closing the serial port.

Step 1: Import PySerial

Step 2: Define Serial Port Settings

ser = serial.Serial( port='COM1', # replace with your COM port baudrate=9600, # set baudrate parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, bytesize=serial.EIGHTBITS )

Step 3: Write to the Serial Port

Step 4: Read from the Serial Port

response = ser.readline() print(response)

Step 5: Close the Serial Port

That’s it! You’ve successfully read and written from a COM port using PySerial in Python while also closing the serial port.

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Short introduction¶

Open port at “38400,8,E,1”, non blocking HW handshaking:

>>> ser = serial.Serial('COM3', 38400, timeout=0, . parity=serial.PARITY_EVEN, rtscts=1) >>> s = ser.read(100) # read up to one hundred bytes . # or as much is in the buffer 

Configuring ports later¶

Get a Serial instance and configure/open it later:

>>> ser = serial.Serial() >>> ser.baudrate = 19200 >>> ser.port = 'COM1' >>> ser Serial(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0) >>> ser.open() >>> ser.is_open True >>> ser.close() >>> ser.is_open False 

with serial.Serial() as ser: ser.baudrate = 19200 ser.port = 'COM1' ser.open() ser.write(b'hello') 

Readline¶

readline() reads up to one line, including the \n at the end. Be careful when using readline() . Do specify a timeout when opening the serial port otherwise it could block forever if no newline character is received. If the \n is missing in the return value, it returned on timeout.

readlines() tries to read “all” lines which is not well defined for a serial port that is still open. Therefore readlines() depends on having a timeout on the port and interprets that as EOF (end of file). It raises an exception if the port is not opened correctly. The returned list of lines do not include the \n .

Both functions call read() to get their data and the serial port timeout is acting on this function. Therefore the effective timeout, especially for readlines() , can be much larger.

Do also have a look at the example files in the examples directory in the source distribution or online.

The eol parameter for readline() is no longer supported when pySerial is run with newer Python versions (V2.6+) where the module io is available.

EOL¶

To specify the EOL character for readline() or to use universal newline mode, it is advised to use io.TextIOWrapper:

import serial import io ser = serial.serial_for_url('loop://', timeout=1) sio = io.TextIOWrapper(io.BufferedRWPair(ser, ser)) sio.write(unicode("hello\n")) sio.flush() # it is buffering. required to get the data out *now* hello = sio.readline() print(hello == unicode("hello\n")) 

Testing ports¶

Listing ports¶

python -m serial.tools.list_ports will print a list of available ports. It is also possible to add a regexp as first argument and the list will only include entries that matched.

The enumeration may not work on all operating systems. It may be incomplete, list unavailable ports or may lack detailed descriptions of the ports.

Accessing ports¶

pySerial includes a small console based terminal program called serial.tools.miniterm . It can be started with python -m serial.tools.miniterm (use option -h to get a listing of all options).

© Copyright 2001-2020, Chris Liechti Revision 31fa4807 .

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