python serial readline with code examples

Python is a very versatile language that finds its use in a variety of applications ranging from web development to data analysis and even automation. One of its key strengths is its ease of use with hardware components. Python-based systems can communicate with devices like microcontrollers, sensors, and other peripherals via different communication protocols like I2C, SPI, and even UART. When it comes to UART communication, the Python 'serial' library provides a convenient way to read from and write to serial ports. In this article, we'll cover how to read from serial ports in Python using the 'serial' library.

Serial Communication Overview

Serial communication refers to a form of data transfer where data is sent one bit at a time over a dedicated communication line. This type of communication is commonly used for low-speed communication between devices that are close together. UART is one of the most commonly used serial communication protocols for connecting devices like sensors, microcontrollers, and other peripherals.

The 'serial' library in Python provides a convenient way to read from and write to serial ports using the UART protocol. Before we dive in, let us first see how to read from a serial port in Python.

Reading from a Serial Port

Reading from a serial port in Python involves the following steps:

1. Import the serial library: We import the serial library to interact with the serial port.

2. Create a serial object: We create a serial object that represents the serial port we want to read from. We can specify the baud rate, port number, parity, stop bit, and other communication parameters while creating the serial object.

3. Read data from the port: We read data from the port using the 'readline' function of the serial library.

4. Close the serial port: We close the serial port when we're done reading data.

Now let us see some code examples on how to read from a serial port.

Code Examples

Example 1: Reading a single line of data

import serial

ser = serial.Serial('/dev/ttyUSB0', 9600) #Open the serial port
data = ser.readline() #Read a single line of data
ser.close() #Close the serial port
print(data)

In this example, we open the serial port '/dev/ttyUSB0' at a baud rate of 9600. We then read a single line of data using the 'readline' function and store it in a variable called 'data'. Finally, we close the serial port and print the data to the console.

Example 2: Reading multiple lines of data

import serial

ser = serial.Serial('/dev/ttyUSB0', 9600) #Open the serial port
while True:
    data = ser.readline() #Read one line of data
    if data:
        print(data.decode().strip()) #Decode and print the data
ser.close() #Close the serial port

In this example, we continuously read data from the serial port in a loop. We read one line of data at a time and check if the data is not empty. If there is data, we decode the data and print it to the console. We continue reading data until the program is interrupted.

In conclusion, Python's 'serial' library makes it easy to read data from a serial port. By following the basic steps outlined above, you can easily read data from a serial port in Python. With this knowledge, you can now start building projects that involve reading data from sensors, microcontrollers, and other peripherals.

let's dive a little deeper into the topic of reading from a serial port in Python using the 'serial' library.

Reading from a Serial Port – More Details

In addition to the basic steps discussed above, there are a few more things to keep in mind while reading data from a serial port in Python:

1. Set the timeout value: When reading data from a serial port, it is important to specify a timeout value. The timeout value specifies the maximum amount of time to wait for data before giving up. If the timeout value is not set, the read operation can block indefinitely, preventing the program from continuing.

2. Decode the data: When reading data from a serial port, it is important to decode the bytes into a string. By default, the data read from a serial port is in bytes. To convert the bytes to a string, we need to use the 'decode' method.

3. Strip the data: When reading data from a serial port, it is common to have leading or trailing characters like newline characters or whitespace. To remove these unwanted characters, we can use the 'strip' method.

Let's update our previous code example to incorporate these additional steps:

import serial

ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1) #Open the serial port with a timeout value
while True:
    data = ser.readline().decode().strip() #Read one line of data, decode, and strip
    if data:
        print(data) #Print the data
ser.close() #Close the serial port

In this updated example, we set a timeout value of 1 second while opening the serial port. We also decode the bytes and strip the leading and trailing characters while reading the data. Finally, we print the data to the console.

Using Serial Port Configuration Parameters

When opening a serial port, there are numerous configuration parameters that you can specify. These parameters include the baud rate, port number, parity, stop bit, and more. The following code example shows how to configure the serial port by specifying many of these parameters:

import serial

ser = serial.Serial(port='/dev/ttyUSB0',
                    baudrate=9600,
                    bytesize=serial.EIGHTBITS, #Number of data bits
                    parity=serial.PARITY_NONE, #Parity checking: none
                    stopbits=serial.STOPBITS_ONE, #Number of stop bits
                    timeout=1) #Timeout value
while True:
    data = ser.readline().decode().strip() #Read one line of data, decode, and strip
    if data:
        print(data) #Print the data
ser.close() #Close the serial port

In this example, we use the 'serial.Serial' method to create a serial object and specify many of the configuration parameters. We set the baud rate to 9600, the number of data bits to 8, parity checking to none, the number of stop bits to 1, and a timeout value of 1 second. We then read data from the serial port in a loop as discussed earlier.

Conclusion

In conclusion, the 'serial' library in Python provides a simple and convenient way to read data from a serial port. By following the basic steps, you can easily read data from a serial port in Python. In addition, the library provides a variety of configuration parameters to fine-tune the serial port communication. With this knowledge, you can start experimenting with reading data from sensors, microcontrollers, and other peripherals using Python.

Popular questions

1. What is serial communication and why is it used?

Serial communication refers to a form of data transfer where data is sent one bit at a time over a dedicated communication line. This type of communication is commonly used for low-speed communication between devices that are close together. Serial communication is used to connect devices like sensors, microcontrollers, and other peripherals.

2. How can we read from a serial port in Python?

We can read from a serial port in Python using the 'serial' library. The basic steps involved in reading from a serial port are importing the serial library, creating a serial object that represents the serial port we want to read from, reading data from the port using the 'readline' or 'read' function of the serial library, and closing the serial port.

3. Why is it important to set the timeout value while reading from a serial port?

When reading data from a serial port, it is important to specify a timeout value. The timeout value specifies the maximum amount of time to wait for data before giving up. If the timeout value is not set, the read operation can block indefinitely, preventing the program from continuing.

4. How do we decode the data read from a serial port in Python?

When reading data from a serial port, the data is usually in bytes. To convert the bytes to a string, we need to use the 'decode' method. This method decodes the bytes using the specified encoding and returns a string.

5. What are some of the configuration parameters that can be specified when opening a serial port using Python?

The 'serial' library provides numerous configuration parameters to specify while opening a serial port. Some of the common parameters include the baud rate, port number, parity checking, number of data bits, number of stop bits, and timeout value. By specifying these parameters, we can fine-tune the serial port communication and ensure compatibility with the peripheral devices connected to the serial port.

Tag

"PySerial"