pyhoff.modbus.SimpleModbusClient#

class pyhoff.modbus.SimpleModbusClient(host, port=502, unit_id=1, timeout=5, debug=False)#

Bases: object

A simple Modbus TCP client

host#

hostname or IP address

Type:

str

port#

server port

Type:

int

unit_id#

ModBus id

Type:

int

timeout#

socket timeout in seconds

Type:

float

last_error#

contains last error message or empty string if no error occurred

Type:

str

debug#

if True prints out transmitted and received bytes in hex

Type:

bool

Instantiate a Modbus TCP client

Parameters:

  • host (str) – hostname or IP address

  • port (int) – server port

  • unit_id (int) – ModBus id

  • timeout (float) – socket timeout in seconds

  • debug (bool) – if True prints out transmitted and received bytes in hex

Example

>>> client = SimpleModbusClient('localhost', port = 502, unit_id = 1)
>>> print(client.read_coils(0, 10))
>>> print(client.read_discrete_inputs(0, 10))
>>> print(client.read_holding_registers(0, 10))
>>> print(client.read_input_registers(0, 10))
>>> print(client.write_single_coil(0, True))
>>> print(client.write_single_register(0, 1234))
>>> print(client.write_multiple_coils(0, [True, False, True]))
>>> print(client.write_multiple_registers(0, [1234, 5678]))
>>> client.close()
close()#

Close connection

Return type:

bytes

Returns:

empty bytes object

connect()#

Connect manual to the configured modbus server. Usually there is no need to call this function since it is handled automatically.

Return type:

bool

read_coil(address)#

Read a coil from the given register address.

Parameters:

address (int) – The register address to read from.

Return type:

bool | None

Returns:

The value of the coil or None if error

read_coils(bit_address, bit_lengths=1)#

ModBus function for reading coils (0x01)

Parameters:

  • bit_address (int) – Bit address (0 to 0xffff)

  • bit_lengths (int) – Number of bits to read (1 to 2000)

Returns:

Bits list or None if error

Return type:

list of bool or None

read_discrete_input(address)#

Read a discrete input from the given register address.

Parameters:

address (int) – The register address to read from.

Return type:

bool | None

Returns:

The value of the discrete input.

read_discrete_inputs(bit_address, bit_lengths=1)#

ModBus function for reading discrete inputs (0x02)

Parameters:

  • bit_address (int) – Bit address (0 to 0xffff)

  • bit_lengths (int) – Number of bits to read (1 to 2000)

Returns:

Bits list or None if error

Return type:

list of bool or None

read_holding_registers(register_address, word_lengths=1)#

ModBus function for reading holding registers (0x03)

Parameters:

  • register_address (int) – Register address (0 to 0xffff)

  • word_lengths (int) – Number of registers to read (1 to 125)

Returns:

Registers list or None if error

Return type:

list of int or None

read_input_registers(register_address, word_lengths=1)#

ModBus function for reading input registers (0x04)

Parameters:

  • register_address (int) – Register address (0 to 0xffff)

  • word_lengths (int) – Number of registers to read (1 to 125)

Returns:

Registers list or None if error

Return type:

list of int or None

receive_modbus_data()#

Receive a ModBus frame

Return type:

bytes

Returns:

bytes received or empty bytes object if an error occurred

send_modbus_data(function_code, body)#

Send raw ModBus TCP frame

Parameters:

  • unction_code – ModBus function code

  • body (bytes) – data

Return type:

int

Returns:

number of transmitted bytes or 0 if transmission failed

write_multiple_coils(bit_address, values)#

ModBus function for writing multiple coils (0x0F)

Parameters:

  • bit_address (int) – Bit address (0 to 0xffff)

  • values (list[bool]) – List of bit values to write

Return type:

bool

Returns:

True if write succeeded or False if failed

write_multiple_registers(register_address, values)#

ModBus function for writing multiple registers (0x10)

Parameters:

  • register_address (int) – Register address (0 to 0xffff)

  • values (list[int]) – List of 16 bit register values to write

Return type:

bool

Returns:

True if write succeeded or False if failed

write_single_coil(bit_address, value)#

ModBus function for writing a single coil (0x05)

Parameters:

  • bit_address (int) – Bit address (0 to 0xffff)

  • value (bool) – Value to write (single bit)

Return type:

bool

Returns:

True if write succeeded or False if failed

write_single_register(register_address, value)#

ModBus function for writing a single register (0x06)

Parameters:

  • register_address (int) – Register address (0 to 0xffff)

  • value (int) – Value to write (0 to 0xffff)

Return type:

bool

Returns:

True if write succeeded or False if failed