modbusfc03 Python

Introduction

Modbus Function Code 03 (FC03) is a Modbus protocol operation that reads the contents of a contiguous block of holding registers in a remote device. It is widely used in industrial automation and builds on a client-server model of communication.

Python, being a versatile and widely used programming language, has several libraries that support Modbus communication, including the popular PyModbus library. In this article, we will explore how to use PyModbus to perform FC03 operations on a remote device.

PyModbus FC03 Example

The following code snippet shows how to use PyModbus to perform an FC03 operation to read a block of holding registers in a remote device.

from pymodbus.client.sync import ModbusTcpClient

# set up the client
client = ModbusTcpClient('localhost', port=502)

# connect to the remote device
client.connect()

# read a block of holding registers starting at address 0
response = client.read_holding_registers(0, 10)

# check if the response is valid
if response.isError():
    print("Error: " + str(response))
else:
    # print the values of the holding registers
    print(response.registers)

# disconnect from the remote device
client.close()

In this example, we first create a ModbusTcpClient object to represent the remote device. We then connect to the device using the connect() method.

We then use the read_holding_registers() method to read a block of 10 holding registers starting from address 0. The response object returned by this method contains the values of the requested holding registers.

We then check if the response is valid by using the isError() method. If the response is valid, we print the values of the holding registers. Finally, we disconnect from the remote device using the close() method.

Conclusion

PyModbus is an easy-to-use library that can be used to perform Modbus communication in Python. In this article, we have seen how to use PyModbus to perform an FC03 operation to read a block of holding registers in a remote device.

It is worth noting that this is just one of the many Modbus operations that can be performed using PyModbus. PyModbus provides support for several Modbus function codes, including read coils (FC01), read discrete inputs (FC02), write multiple coils (FC15), and write multiple registers (FC16).