ModbusRTUTransport

class ModbusRTUTransport(

port: str,

baudrate: int = 9600,

parity: Literal['N', 'E', 'O'] = 'N',

stopbits: Literal[1, 2] = 1,

bytesize: Literal[5, 6, 7, 8] = 8,

timeout: float = 3.0,

framer: Literal['rtu', 'ascii'] = 'rtu',

)

Bases: ModbusTransport

A Modbus serial line (RTU or ASCII framing). One port, addressed per wire op via unit_id.

Validate and store the serial port’s fields.

Attributes

is_open

Whether the client has been opened and not closed.

Methods

check_unit_id	Validate unit_id against this physical layer's range (0 to _max_unit_id) and return it.
close	Close and teardown; with a holder, remove it and tear down only when the last owner leaves.
lock	Return the reentrant resource lock for atomic multi-step sequences; the holder may write/query/read inside it.
open	Open the connection (idempotent); with a holder, admit it and return True only for the first owner.
read_coils	Read coils by address (FC01).
read_discrete_inputs	Read discrete inputs by address (FC02).
read_holding_registers	Read holding registers by address (FC03).
read_input_registers	Read input registers by address (FC04).
read_typed	Read address as data_type, dispatching by register_type and decoding across registers.
write_coil	Write a single coil by address (FC05).
write_coils	Write multiple coils by address (FC15).
write_holding_register	Write a single holding register by address (FC06).
write_holding_registers	Write multiple holding registers by address (FC16).
write_typed	Encode value as data_type and write it to address, dispatching by register_type.

check_unit_id(unit_id: int) → int

Validate unit_id against this physical layer’s range (0 to _max_unit_id) and return it.

close(holder: object | None = None) → None

Close and teardown; with a holder, remove it and tear down only when the last owner leaves.

A holder that needs to talk to the instrument before the connection goes (releasing a remote lock, say) does that in its own close before calling this, while the session is still up.

Raises UnknownHolderError when an unrecognized holder closes while others still own the connection, because that is the case where ignoring it silently strands the real owners and leaves the connection open forever. Once the last owner has left there is nothing to strand, so a repeat close is a no-op and close stays idempotent.

property is_open: bool

Whether the client has been opened and not closed. Stays True across a dropped socket, which the next op reconnects.

lock() → RLock

Return the reentrant resource lock for atomic multi-step sequences; the holder may write/query/read inside it.

open(holder: object | None = None) → bool

Open the connection (idempotent); with a holder, admit it and return True only for the first owner.

read_coils(

address: int,

count: int,

*,

unit_id: int,

) → list[bool]

Read coils by address (FC01).

read_discrete_inputs(

address: int,

count: int,

*,

unit_id: int,

) → list[bool]

Read discrete inputs by address (FC02).

read_holding_registers(

address: int,

count: int,

*,

unit_id: int,

) → list[int]

Read holding registers by address (FC03).

read_input_registers(

address: int,

count: int,

*,

unit_id: int,

) → list[int]

Read input registers by address (FC04).

read_typed(

register_type: Literal['holding', 'input', 'coil', 'discrete'],

address: int,

data_type: Literal['uint16', 'int16', 'uint32', 'int32', 'uint64', 'int64', 'float32', 'float64', 'bool'],

*,

unit_id: int,

byte_swap: bool = False,

word_swap: bool = False,

long_swap: bool = False,

) → int | float | bool

Read address as data_type, dispatching by register_type and decoding across registers.

Coils and discrete inputs are single-bit, so data_type must be "bool" and the read returns a bool.

write_coil(

address: int,

value: bool,

*,

unit_id: int,

) → None

Write a single coil by address (FC05).

write_coils(

address: int,

values: list[bool],

*,

unit_id: int,

) → None

Write multiple coils by address (FC15).

write_holding_register(

address: int,

value: int,

*,

unit_id: int,

) → None

Write a single holding register by address (FC06).

write_holding_registers(

address: int,

values: list[int],

*,

unit_id: int,

) → None

Write multiple holding registers by address (FC16).

write_typed(

register_type: Literal['holding', 'input', 'coil', 'discrete'],

address: int,

value: int | float | bool,

data_type: Literal['uint16', 'int16', 'uint32', 'int32', 'uint64', 'int64', 'float32', 'float64', 'bool'],

*,

unit_id: int,

byte_swap: bool = False,

word_swap: bool = False,

long_swap: bool = False,

) → None

Encode value as data_type and write it to address, dispatching by register_type.

Coils are single-bit, so data_type must be "bool" and value must be a bool (no numeric coercion).