Serial

Native pyserial support for serial communication

Native pyserial support for serial communication with your DUT.

Import

import serial

Methods

Method	Description
Serial()	Create serial connection
readline()	Read a line
read()	Read specified bytes
read_until()	Read until delimiter
write()	Write data
open()	Open connection
close()	Close connection
is_open	Check connection state

Method Reference

serial.Serial(port, baudrate, **kwargs)

Create a serial connection.

import serial

ser = serial.Serial('/dev/ttyUSB1', 115200)

# With additional parameters
ser = serial.Serial(
    port='/dev/ttyUSB1',
    baudrate=115200,
    timeout=60,
    bytesize=serial.EIGHTBITS,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE
)

Parameters:

Parameter	Type	Description
port	str	Serial port path (e.g., /dev/ttyUSB1)
baudrate	int	Baud rate in bits per second
timeout	float	Read timeout in seconds
bytesize	int	Data bits (5, 6, 7, or 8)
parity	str	Parity (PARITY_NONE, PARITY_EVEN, PARITY_ODD)
stopbits	int	Stop bits (1, 1.5, or 2)

Returns: Serial object

readline()

Read a line from the serial port.

line = ser.readline()
print(f"Received: {line.decode('utf-8').strip()}")

Returns: bytes - The received line

read(size)

Read a specified number of bytes.

data = ser.read(10)

Parameter	Type	Description
size	int	Number of bytes to read

Returns: bytes - The received data

read_until(expected=b'\n', size=None)

Read until expected sequence is found.

line = ser.read_until(b'\n')

Parameter	Type	Description
expected	bytes	Sequence to read until
size	int	Maximum bytes to read

Returns: bytes - Data up to expected sequence

write(data)

Write data to the serial port.

ser.write(b'AT+VER\r\n')

Parameter	Type	Description
data	bytes	Data to write

Returns: int - Number of bytes written

close()

Close the serial connection.

ser.close()

is_open

Check if connection is open.

if ser.is_open:
    print("Connected")

Returns: bool - True if connection is open

Examples

Basic Communication

import serial
import time

ser = serial.Serial('/dev/ttyUSB1', 115200, timeout=60)

# Send command
ser.write(b'AT+VER\r\n')
time.sleep(0.1)

# Read response
response = ser.readline()
print(f"Response: {response.decode('utf-8').strip()}")

ser.close()

Interactive Session

import serial

def interactive_session(port, baudrate=115200):
    ser = serial.Serial(port, baudrate, timeout=1)
    print(f"Connected to {port}")

    while True:
        try:
            # Read any available data
            if ser.in_waiting:
                data = ser.read(ser.in_waiting)
                print(data.decode('utf-8'), end='')

            # Get user input
            command = input()
            if command.lower() == 'quit':
                break

            ser.write(f"{command}\r\n".encode('utf-8'))

        except KeyboardInterrupt:
            break

    ser.close()

Data Logging

import serial
import time
from datetime import datetime

def log_serial(port, log_file, duration=60):
    ser = serial.Serial(port, 115200, timeout=1)

    with open(log_file, 'w') as f:
        start = time.time()

        while time.time() - start < duration:
            if ser.in_waiting:
                data = ser.read(ser.in_waiting)
                timestamp = datetime.now().isoformat()
                f.write(f"[{timestamp}] {data.decode('utf-8')}")
                f.flush()

            time.sleep(0.1)

    ser.close()

Command/Response Pattern

import serial
import time

class SerialDevice:
    def __init__(self, port, baudrate=115200):
        self.ser = serial.Serial(port, baudrate, timeout=60)

    def send_command(self, command, timeout=5):
        self.ser.reset_input_buffer()
        self.ser.write(f"{command}\r\n".encode('utf-8'))

        response = ""
        start = time.time()

        while time.time() - start < timeout:
            if self.ser.in_waiting:
                line = self.ser.readline().decode('utf-8').strip()
                response += line + "\n"

            time.sleep(0.1)

        return response

    def close(self):
        self.ser.close()

# Usage
device = SerialDevice('/dev/ttyUSB1')
response = device.send_command('AT+VER')
print(response)
device.close()

Hardware Integration

Connection	Description
Raw UART	Direct TX/RX line connections
USB CDC	Virtual serial over USB
Flow Control	Hardware (RTS/CTS) and software (XON/XOFF)

Notes

• Lager supports native pyserial for serial communication
• Serial ports are designated during Lager setup configuration
• Supports both raw UART and USB CDC connections
• Default baud rate is 115200
• Always handle SerialException errors appropriately
• Use decode('utf-8') for string conversion