class tinymodbusrtu.TinyModbusRtu(serial_connection: Serial = None, crc_enabled: bool = True, timeout: float = 0.5)

TinyModbusRtu Class for communicating with Modbus RTU

Supports Modbus RTU Protocol over Serial ONLY.

NOT SUPPORTED: ASCII Protocol, Modbus over TCP

Allows the following messages:

Standard Modbus RTU Read requests, Standard Modbus RTU Write requests, Fully custom Modbus RTU requests, Custom function code trigger requests

Allows Optionally Disabling the CRC16 Validity check for Hobbyist Development

Note: Disables CRC16 Check for both requests and responses

See Official Modbus Documentation for RTU request formatting:

https://www.modbustools.com/modbus.html

send(message: RtuMessage) → None

Send Byte Message on underlying serial connection

Parameters:

message – message to send

listen() → RtuMessage

Listen for incoming messages Terminates upon receiving a complete message, must call listen() again to receive another message

Returns:

message received

property crc_enabled: bool

class tinymodbusrtu.TinyModbusClient(serial_connection: Serial = None, crc_enabled: bool = True, timeout: float = 0.5)

Client Object for communicating with one or more MODBUS RTU Servers

read_coils(server_id: int, address: int, count: int) → bytes

Sends Modbus RTU request to read server coils

Parameters:

• server_id – Intended recipient

• address – Starting coil address

• count – Count of coils to read

Returns:

Data of response

read_discrete_inputs(server_id: int, address: int, count: int) → bytes

Sends Modbus RTU request to read server discrete inputs

Parameters:

• server_id – Intended recipient

• address – Starting discrete input address

• count – Count of disrete inputs to read

Returns:

Data of response

read_holding_registers(server_id: int, address: int, count: int) → bytes

Sends Modbus RTU request to read server holding registers

Parameters:

• server_id – Intended recipient

• address – Starting holding register address

• count – Count of holding registers to read

Returns:

Data of response

read_input_registers(server_id: int, address: int, count: int) → bytes

Sends Modbus RTU request to read server input registers

Parameters:

• server_id – Intended recipient

• address – Starting input register address

• count – Count of input registers to read

Returns:

Data of response

write_single_coil(server_id: int, address: int, coil_status: int) → bool

Sends Modbus RTU request to write a single coil to “ON”(65280) or “OFF”(0) Recommend using module attributes COIL_ON and COIL_OFF

Parameters:

• server_id – Intended recipient

• address – Coil Address to be written

• coil_status – Coil Status to be set

Returns:

True if coil written successfully, False otherwise

write_single_register(server_id: int, address: int, value: int) → bool

Sends Modbus RTU request to write a single register to a given value

Parameters:

• server_id – Intended recipient

• address – Register Address to Write

• value – Value to be written to Register

Returns:

True if register written successfully, False otherwise

write_multiple_coils(server_id: int, starting_address: int, values: list[bool]) → bool

Sends Modbus RTU request to write multiple coils to ‘ON’ or ‘OFF from a given list

Not Supported in this version of TinyModbusRtu

Parameters:

• server_id – Intended recipient

• starting_address – Starting Address of Coils to Write

• values – List of values to write to Coils in Order

Returns:

True if write operation is successful, False otherwise

write_multiple_registers(server_id: int, starting_address: int, values: list[int]) → bool

Sends Modbus RTU request to write multiple registers to values in a given list

Parameters:

• server_id – Intended recipient

• starting_address – Starting Address of Registers to Write

• values – List of values to write to Registers in Order

Returns:

True if write operation is successful, False otherwise

send_function_code(server_id: int, function_code: int) → bytes

Send only a custom function code to a server

Parameters:

• server_id – Intended recipient

• function_code – Custom function code

send_custom_message(server_id: int, function_code: int, data_bytes: bytes) → bytes

Send a fully custom message to a server

Parameters:

• server_id – Intended recipient

• function_code – Custom function code

• data_bytes – Custom message contents

property crc_enabled: bool

listen() → RtuMessage

Listen for incoming messages Terminates upon receiving a complete message, must call listen() again to receive another message

Returns:

message received

send(message: RtuMessage) → None

Send Byte Message on underlying serial connection

Parameters:

message – message to send

class tinymodbusrtu.TinyModbusServer(serial_connection=None, server_id=0, crc_enabled=True)

listen() → RtuMessage

Listen for incoming messages Terminates upon receiving a complete message, must call listen() again to receive another message

Returns:

message received

send(message: RtuMessage) → None

Send Byte Message on underlying serial connection

Parameters:

message – message to send

class tinymodbusrtu.RtuMessage(server_id: int = None, function_code: int = None, data_bytes: bytes = b'', crc_bytes: bytes = b'')

Initiate an RtuMessage object

Parameters:

• server_id – Server Id of intended message recipient

• function_code – Function Code of action to be performed

• data_bytes – Raw data bytes of message

• crc_bytes – Bytes for crc16 integrity check

decode(message: bytes, crc_enabled: bool) → None

Decode a raw message string to the applicable parts

Parameters:

• message – Bytes message to decode

• crc_enabled – Whether the message contains crc_bytes

encode(crc_enabled: bool) → bytes

Encodes Message object into serial writable bytes

Returns:

Serial writable message

set_crc(crc_bytes: bytes) → None

Set the CRC16 byte value

Parameters:

crc_bytes – new crc bytes to append to message

property server_id: int

property function_code: int

property data_bytes: bytes

property crc_bytes: bytes

property length: int

class tinymodbusrtu.RtuRequest(server_id: int = None, function_code: int = None, address: int = None, count: int = None, value: int = None, crc_bytes: bytes = b'')

Rtu Request Object

Parameters:

• server_id – Intended Recipient’s Server Id

• function_code – Function Code of Request

• address – Address to Start Reading OR Address to Write

• count – Count of Registers to Read, Do Not Provide for Write Requests

• value – Value to Write to Given Address, Do Not Provide for Read Requests

• crc_bytes – crc16 Value of Request

property address: int

property count: int

property crc_bytes: bytes

property data_bytes: bytes

decode(message: bytes, crc_enabled: bool) → None

Decode a raw message string to the applicable parts

Parameters:

• message – Bytes message to decode

• crc_enabled – Whether the message contains crc_bytes

encode(crc_enabled: bool) → bytes

Encodes Message object into serial writable bytes

Returns:

Serial writable message

property function_code: int

property length: int

property server_id: int

set_crc(crc_bytes: bytes) → None

Set the CRC16 byte value

Parameters:

crc_bytes – new crc bytes to append to message

property value: int

class tinymodbusrtu.RtuResponse(server_id: int = None, function_code: int = None, byte_count: int = None, response_data: list[int] = None, crc_bytes: bytes = b'')

Rtu Response Object

Parameters:

• server_id –

• function_code –

• byte_count –

• response_data –

Crc_bytes:

property crc_bytes: bytes

property data_bytes: bytes

decode(message: bytes, crc_enabled: bool) → None

Decode a raw message string to the applicable parts

Parameters:

• message – Bytes message to decode

• crc_enabled – Whether the message contains crc_bytes

encode(crc_enabled: bool) → bytes

Encodes Message object into serial writable bytes

Returns:

Serial writable message

property function_code: int

property length: int

property server_id: int

set_crc(crc_bytes: bytes) → None

Set the CRC16 byte value

Parameters:

crc_bytes – new crc bytes to append to message