UART RS 485 modbus connection is not working on PI 3B/2B 64 bit debian OS( bookworm/trixie)

[anil7385]

I have set up the PI 3B/2B devices with 64 bit OS ( bookworm & Trixie ) and tested UART RS 485 connection, it is found that the RS-485 libmodbus communication is not working.

I have done all the necessary settings in /boot/firmware/config.txt file to get the UART enable, but still it is failing, below is the settings from config.txt file for your reference.

[all]
enable_uart=1
dtoverlay=disable-bt
dtoverlay=miniuart-bt
dtoverlay=uart0-pi2,rs485,rts_inverted=1
dtoverlay=uart0-rts485

I am using the RPI enabled libmodbus library, where switching between DE/RE is done using the function - modbus_configure_rpi_bcm_pins.
Below is the is the code from Master –

def get_Modbus_client(device="/dev/serial0".encode("ascii"), baud=9600, parity="N".encode("ascii"), data_bit=8, stop_bit=1, timeout=1.5, slave_id=1):
client = None
if is_simulated_environment():
try:
client = Modbus_Windows_Client()
except:
print("Exception")
else:
client = ModbusRtu(device, baud, parity, data_bit, stop_bit)
timeout_sec = client.get_response_timeout()

if client:
    client.set_response_timeout(timeout)
    # Connect
    r = client.connect()
    client.flush()

    BCM_PIN_DE = 18
    BCM_PIN_RE = 18

    # Set Slave ID number
    client.set_slave(slave_id)

    # Enable RPi GPIO Functions
    # client.enable_rpi(1)

    # Define pin numbers to be used as Read Enable (RE) and Drive Enable (DE)
    client.configure_rpi_bcm_pins(BCM_PIN_DE, BCM_PIN_RE)

    # Export pin direction (set as outputs)
    client.rpi_pin_export_direction()

return client

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Kindly check the same and do let me know if I am missing any settings/ parameters to be set which could cause this issue.