LINUX的RS485modbus通讯代码

以下是一个基于Python的RS485 Modbus通信代码示例：

import serial
import time

# Configure the serial port
ser = serial.Serial(
    port='/dev/ttyUSB0',      # Port used by the RS485 converter
    baudrate=9600,            # Baud rate
    bytesize=serial.EIGHTBITS, # Number of data bits
    parity=serial.PARITY_NONE, # Parity
    stopbits=serial.STOPBITS_ONE, # Number of stop bits
    timeout=1                   # Timeout in seconds
)

# Function to calculate the Modbus CRC
def calculate_crc(data):
    crc = 0xFFFF
    for i in range(len(data)):
        crc ^= ord(data[i])
        for j in range(8):
            if crc & 0x0001:
                crc >>= 1
                crc ^= 0xA001
            else:
                crc >>= 1
    return chr(crc & 0xFF) + chr(crc >> 8)

# Function to read a Modbus register
def read_register(address, register):
    # Build the Modbus request
    data = chr(address) + "\x03" + chr(register >> 8) + chr(register & 0xFF) + "\x00\x01"
    # Calculate the CRC
    crc = calculate_crc(data)
    # Send the request
    ser.write(data + crc)
    # Wait for the response
    time.sleep(0.1)
    # Read the response
    response = ser.read(ser.inWaiting())
    # Check if the response is valid
    if len(response) == 5 and response[0] == chr(address) and response[1] == "\x03" and response[2] == "\x02":
        # Extract the register value
        value = (ord(response[3]) << 8) + ord(response[4])
        return value
    else:
        return None

# Example usage
value = read_register(1, 0x0000)
if value is not None:
    print("Register 0x0000 value is:", value)
else:
    print("Error reading register 0x0000")

注：此代码示例假定已经安装了PySerial库。