Fyi this is my code

import os import logging import threading import serial import minimalmodbus

os.system("sudo chmod 777 /dev/ttyS0") os.system("sudo chown pi:pi /dev/ttyS0")

logging.basicConfig() log = logging.getLogger() log.setLevel(logging.DEBUG)

Define your custom logic to read coil values

def your_custom_logic_to_read_coils(coil_address, coil_count): # Implement your logic to read coil values from the slave # Replace this with your own implementation # Example: Read coil values from hardware or memory # Return a list of coil values corresponding to the requested address and count return [False] * coil_count # Example: Return a list of False values

Subclass the RtuSlave to handle incoming Modbus requests

class CustomModbusSlave(minimalmodbus.RtuSlave): def _process(self, request): if request.functioncode == 1: # Modbus function code 01: Read Coils coil_address = request.address coil_count = request.count coil_values = your_custom_logic_to_read_coils(coil_address, coil_count) response_pdu = self._response_pdu(request.functioncode, coil_values) self._send(response_pdu)

Run the Modbus RTU Slave in a separate thread

def run_modbus_server(): # Define the serial port parameters serial_port_name = '/dev/ttyS0' baud_rate = 9600 parity = serial.PARITY_NONE data_bits = 8 stop_bits = 1

# Create the serial port object
serial_port = serial.Serial(
    port=serial_port_name,
    baudrate=baud_rate,
    parity=parity,
    bytesize=data_bits,
    stopbits=stop_bits,
)

# Create the Modbus RTU Slave context
instrument = CustomModbusSlave(port=serial_port, slaveaddress=2)

# Start the Modbus RTU Slave server
while True:
    instrument.handle_request()  # Process incoming Modbus requests

server_thread = threading.Thread(target=run_modbus_server) server_thread.start()