# pymodbus package

## Pymodbus: Modbus Protocol Implementation

TwistedModbus is built on top of the code developed by:

> Copyright (c) 2001-2005 S.W.A.C. GmbH, Germany. Copyright (c) 2001-2005 S.W.A.C. Bohemia s.r.o., Czech Republic. Hynek Petrak <hynek@swac.cz>

Released under the the BSD license

## Subpackages

- pymodbus.client package
  - Subpackages
    - pymodbus.client.asynchronous package
      - Async Modbus Client implementation based on Twisted, tornado and asyncio
      - Subpackages
        - pymodbus.client.asynchronous.asyncio package
        - pymodbus.client.asynchronous.factory package
          - Submodules
          - pymodbus.client.asynchronous.factory.serial module
          - pymodbus.client.asynchronous.factory.tcp module
          - pymodbus.client.asynchronous.factory.udp module
        - pymodbus.client.asynchronous.schedulers package
        - pymodbus.client.asynchronous.tornado package
        - pymodbus.client.asynchronous.twisted package
          - Implementation of a Modbus Client Using Twisted
      - Submodules
      - pymodbus.client.asynchronous.serial module
      - pymodbus.client.asynchronous.tcp module
      - pymodbus.client.asynchronous.thread module
      - pymodbus.client.asynchronous.udp module
  - Submodules
  - pymodbus.client.common module
    - Modbus Client Common
  - pymodbus.client.sync module
- pymodbus.datastore package
  - Subpackages
    - pymodbus.datastore.database package
      - Submodules
      - pymodbus.datastore.database.redis_datastore module
      - pymodbus.datastore.database.sql_datastore module
  - Submodules
  - pymodbus.datastore.context module
  - pymodbus.datastore.remote module
  - pymodbus.datastore.store module
    - Modbus Server Datastore
    - Datastore Implementation
- pymodbus.framer package
  - Submodules
  - pymodbus.framer.ascii_framer module
  - pymodbus.framer.binary_framer module
  - pymodbus.framer.rtu_framer module
  - pymodbus.framer.socket_framer module
  - Module contents
- pymodbus.internal package
  - Submodules
  - pymodbus.internal.ptwisted module
- pymodbus.server package
  - Submodules
  - pymodbus.server.asynchronous module
    - Implementation of a Twisted Modbus Server
  - pymodbus.server.sync module
    - Implementation of a Threaded Modbus Server
- pymodbus.repl package
  - Submodules
  - pymodbus.repl.client module
  - pymodbus.repl.completer module
  - pymodbus.repl.helper module
  - pymodbus.repl.main module

## Submodules

## pymodbus.bit_read_message module

### Bit Reading Request/Response messages

class `pymodbus.bit_read_message.``ReadCoilsRequest`(address=None, count=None, **kwargs)

  Bases: `pymodbus.bit_read_message.ReadBitsRequestBase`

  This function code is used to read from 1 to 2000(0x7d0) contiguous status of coils in a remote device. The Request PDU specifies the starting address, ie the address of the first coil specified, and the number of coils. In the PDU Coils are addressed starting at zero. Therefore coils numbered 1-16 are addressed as 0-15.

  `execute`(context)

    Run a read coils request against a datastore

    Before running the request, we make sure that the request is in the max valid range (0x001-0x7d0). Next we make sure that the request is valid against the current datastore.

    Parameters: | context – The datastore to request from
    Returns: | The initializes response message, exception message otherwise

  `function_code` = 1

class `pymodbus.bit_read_message.``ReadCoilsResponse`(values=None, **kwargs)

  Bases: `pymodbus.bit_read_message.ReadBitsResponseBase`

  The coils in the response message are packed as one coil per bit of the data field. Status is indicated as 1= ON and 0= OFF. The LSB of the first data byte contains the output addressed in the query. The other coils follow toward the high order end of this byte, and from low order to high order in subsequent bytes.

  If the returned output quantity is not a multiple of eight, the remaining bits in the final data byte will be padded with zeros (toward the high order end of the byte). The Byte Count field specifies the quantity of complete bytes of data.

  `function_code` = 1

class `pymodbus.bit_read_message.``ReadDiscreteInputsRequest`(address=None, count=None, **kwargs)

  Bases: `pymodbus.bit_read_message.ReadBitsRequestBase`

  This function code is used to read from 1 to 2000(0x7d0) contiguous status of discrete inputs in a remote device. The Request PDU specifies the starting address, ie the address of the first input specified, and the number of inputs. In the PDU Discrete Inputs are addressed starting at zero. Therefore Discrete inputs numbered 1-16 are addressed as 0-15.

  `execute`(context)

    Run a read discrete input request against a datastore

    Before running the request, we make sure that the request is in the max valid range (0x001-0x7d0). Next we make sure that the request is valid against the current datastore.

    Parameters: | context – The datastore to request from
    Returns: | The initializes response message, exception message otherwise

  `function_code` = 2

class `pymodbus.bit_read_message.``ReadDiscreteInputsResponse`(values=None, **kwargs)

  Bases: `pymodbus.bit_read_message.ReadBitsResponseBase`

  The discrete inputs in the response message are packed as one input per bit of the data field. Status is indicated as 1= ON; 0= OFF. The LSB of the first data byte contains the input addressed in the query. The other inputs follow toward the high order end of this byte, and from low order to high order in subsequent bytes.

  If the returned input quantity is not a multiple of eight, the remaining bits in the final data byte will be padded with zeros (toward the high order end of the byte). The Byte Count field specifies the quantity of complete bytes of data.

  `function_code` = 2

## pymodbus.bit_write_message module

### Bit Writing Request/Response

TODO write mask request/response

class `pymodbus.bit_write_message.``WriteSingleCoilRequest`(address=None, value=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to write a single output to either ON or OFF in a remote device.

  The requested ON/OFF state is specified by a constant in the request data field. A value of FF 00 hex requests the output to be ON. A value of 00 00 requests it to be OFF. All other values are illegal and will not affect the output.

  The Request PDU specifies the address of the coil to be forced. Coils are addressed starting at zero. Therefore coil numbered 1 is addressed as 0. The requested ON/OFF state is specified by a constant in the Coil Value field. A value of 0XFF00 requests the coil to be ON. A value of 0X0000 requests the coil to be off. All other values are illegal and will not affect the coil.

  `decode`(data)

    Decodes a write coil request

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes write coil request

    Returns: | The byte encoded message

  `execute`(context)

    Run a write coil request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | The populated response or exception message

  `function_code` = 5
  `get_response_pdu_size`()

    Func_code (1 byte) + Output Address (2 byte) + Output Value (2 Bytes) :return:

class `pymodbus.bit_write_message.``WriteSingleCoilResponse`(address=None, value=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response is an echo of the request, returned after the coil state has been written.

  `decode`(data)

    Decodes a write coil response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes write coil response

    Returns: | The byte encoded message

  `function_code` = 5

class `pymodbus.bit_write_message.``WriteMultipleCoilsRequest`(address=None, values=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  “This function code is used to force each coil in a sequence of coils to either ON or OFF in a remote device. The Request PDU specifies the coil references to be forced. Coils are addressed starting at zero. Therefore coil numbered 1 is addressed as 0.

  The requested ON/OFF states are specified by contents of the request data field. A logical ‘1’ in a bit position of the field requests the corresponding output to be ON. A logical ‘0’ requests it to be OFF.”

  `decode`(data)

    Decodes a write coils request

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes write coils request

    Returns: | The byte encoded message

  `execute`(context)

    Run a write coils request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | The populated response or exception message

  `function_code` = 15
  `get_response_pdu_size`()

    Func_code (1 byte) + Output Address (2 byte) + Quantity of Outputs (2 Bytes) :return:

class `pymodbus.bit_write_message.``WriteMultipleCoilsResponse`(address=None, count=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response returns the function code, starting address, and quantity of coils forced.

  `decode`(data)

    Decodes a write coils response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes write coils response

    Returns: | The byte encoded message

  `function_code` = 15

## pymodbus.compat module

### Python 2.x/3.x Compatibility Layer

This is mostly based on the jinja2 compat code:

> Some py2/py3 compatibility support based on a stripped down version of six so we don’t have to depend on a specific version of it.

> copyright: | Copyright 2013 by the Jinja team, see AUTHORS.
> license: | BSD, see LICENSE for details.

`pymodbus.compat.``byte2int`(b)

`pymodbus.compat.``implements_to_string`(x)

`pymodbus.compat.``int2byte`()

  S.pack(v1, v2, …) -> bytes

  Return a bytes object containing values v1, v2, … packed according to the format string S.format. See help(struct) for more on format strings.

`pymodbus.compat.``is_installed`(module)

## pymodbus.constants module

### Constants For Modbus Server/Client

This is the single location for storing default values for the servers and clients.

class `pymodbus.constants.``Defaults`

  Bases: `pymodbus.interfaces.Singleton`

  A collection of modbus default values

  `Port`

    The default modbus tcp server port (502)

  `Retries`

    The default number of times a client should retry the given request before failing (3)

  `RetryOnEmpty`

    A flag indicating if a transaction should be retried in the case that an empty response is received. This is useful for slow clients that may need more time to process a requst.

  `Timeout`

    The default amount of time a client should wait for a request to be processed (3 seconds)

  `Reconnects`

    The default number of times a client should attempt to reconnect before deciding the server is down (0)

  `TransactionId`

    The starting transaction identifier number (0)

  `ProtocolId`

    The modbus protocol id. Currently this is set to 0 in all but proprietary implementations.

  `UnitId`

    The modbus slave addrss. Currently this is set to 0x00 which means this request should be broadcast to all the slave devices (really means that all the devices should respons).

  `Baudrate`

    The speed at which the data is transmitted over the serial line. This defaults to 19200.

  `Parity`

    The type of checksum to use to verify data integrity. This can be on of the following:

        - (E)ven - 1 0 1 0 | P(0)
        - (O)dd  - 1 0 1 0 | P(1)
        - (N)one - 1 0 1 0 | no parity

    This defaults to (N)one.

  `Bytesize`

    The number of bits in a byte of serial data. This can be one of 5, 6, 7, or 8. This defaults to 8.

  `Stopbits`

    The number of bits sent after each character in a message to indicate the end of the byte. This defaults to 1.

  `ZeroMode`

    Indicates if the slave datastore should use indexing at 0 or 1. More about this can be read in section 4.4 of the modbus specification.

  `IgnoreMissingSlaves`

    In case a request is made to a missing slave, this defines if an error should be returned or simply ignored. This is useful for the case of a serial server emulater where a request to a non-existant slave on a bus will never respond. The client in this case will simply timeout.

  `Baudrate` = 19200
  `Bytesize` = 8
  `IgnoreMissingSlaves` = False
  `Parity` = 'N'
  `Port` = 502
  `ProtocolId` = 0
  `ReadSize` = 1024
  `Reconnects` = 0
  `Retries` = 3
  `RetryOnEmpty` = False
  `Stopbits` = 1
  `Timeout` = 3
  `TransactionId` = 0
  `UnitId` = 0
  `ZeroMode` = False

class `pymodbus.constants.``ModbusStatus`

  Bases: `pymodbus.interfaces.Singleton`

  These represent various status codes in the modbus protocol.

  `Waiting`

    This indicates that a modbus device is currently waiting for a given request to finish some running task.

  `Ready`

    This indicates that a modbus device is currently free to perform the next request task.

  `On`

    This indicates that the given modbus entity is on

  `Off`

    This indicates that the given modbus entity is off

  `SlaveOn`

    This indicates that the given modbus slave is running

  `SlaveOff`

    This indicates that the given modbus slave is not running

  `Off` = 0
  `On` = 65280
  `Ready` = 0
  `SlaveOff` = 0
  `SlaveOn` = 255
  `Waiting` = 65535

class `pymodbus.constants.``Endian`

  Bases: `pymodbus.interfaces.Singleton`

  An enumeration representing the various byte endianess.

  `Auto`

    This indicates that the byte order is chosen by the current native environment.

  `Big`

    This indicates that the bytes are in little endian format

  `Little`

    This indicates that the bytes are in big endian format

  Note

  I am simply borrowing the format strings from the python struct module for my convenience.

  `Auto` = '@'
  `Big` = '>'
  `Little` = '<'

class `pymodbus.constants.``ModbusPlusOperation`

  Bases: `pymodbus.interfaces.Singleton`

  Represents the type of modbus plus request

  `GetStatistics`

    Operation requesting that the current modbus plus statistics be returned in the response.

  `ClearStatistics`

    Operation requesting that the current modbus plus statistics be cleared and not returned in the response.

  `ClearStatistics` = 4
  `GetStatistics` = 3

class `pymodbus.constants.``DeviceInformation`

  Bases: `pymodbus.interfaces.Singleton`

  Represents what type of device information to read

  `Basic`

    This is the basic (required) device information to be returned. This includes VendorName, ProductCode, and MajorMinorRevision code.

  `Regular`

    In addition to basic data objects, the device provides additional and optinoal identification and description data objects. All of the objects of this category are defined in the standard but their implementation is optional.

  `Extended`

    In addition to regular data objects, the device provides additional and optional identification and description private data about the physical device itself. All of these data are device dependent.

  `Specific`

    Request to return a single data object.

  `Basic` = 1
  `Extended` = 3
  `Regular` = 2
  `Specific` = 4

class `pymodbus.constants.``MoreData`

  Bases: `pymodbus.interfaces.Singleton`

  Represents the more follows condition

  `Nothing`

    This indiates that no more objects are going to be returned.

  `KeepReading`

    This indicates that there are more objects to be returned.

  `KeepReading` = 255
  `Nothing` = 0

## pymodbus.device module

### Modbus Device Controller

These are the device management handlers. They should be maintained in the server context and the various methods should be inserted in the correct locations.

class `pymodbus.device.``ModbusAccessControl`

  Bases: `pymodbus.interfaces.Singleton`

  This is a simple implementation of a Network Management System table. Its purpose is to control access to the server (if it is used). We assume that if an entry is in the table, it is allowed accesses to resources. However, if the host does not appear in the table (all unknown hosts) its connection will simply be closed.

  Since it is a singleton, only one version can possible exist and all instances pull from here.

  `add`(host)

    Add allowed host(s) from the NMS table

    Parameters: | host – The host to add

  `check`(host)

    Check if a host is allowed to access resources

    Parameters: | host – The host to check

  `remove`(host)

    Remove allowed host(s) from the NMS table

    Parameters: | host – The host to remove

class `pymodbus.device.``ModbusPlusStatistics`

  Bases: `object`

  This is used to maintain the current modbus plus statistics count. As of right now this is simply a stub to complete the modbus implementation. For more information, see the modbus implementation guide page 87.

  `encode`()

    Returns a summary of the modbus plus statistics

    Returns: | 54 16-bit words representing the status

  `reset`()

    This clears all of the modbus plus statistics

  `summary`()

    Returns a summary of the modbus plus statistics

    Returns: | 54 16-bit words representing the status

class `pymodbus.device.``ModbusDeviceIdentification`(info=None)

  Bases: `object`

  This is used to supply the device identification for the readDeviceIdentification function

  For more information read section 6.21 of the modbus application protocol.

  `MajorMinorRevision`
  `ModelName`
  `ProductCode`
  `ProductName`
  `UserApplicationName`
  `VendorName`
  `VendorUrl`
  `summary`()

    Return a summary of the main items

    Returns: | An dictionary of the main items

  `update`(value)

    Update the values of this identity using another identify as the value

    Parameters: | value – The value to copy values from

class `pymodbus.device.``DeviceInformationFactory`

  Bases: `pymodbus.interfaces.Singleton`

  This is a helper factory that really just hides some of the complexity of processing the device information requests (function code 0x2b 0x0e).

  classmethod `get`(control, read_code=1, object_id=0)

    Get the requested device data from the system

    Parameters:

    - control – The control block to pull data from
    - read_code – The read code to process
    - object_id – The specific object_id to read

    Returns: | The requested data (id, length, value)

class `pymodbus.device.``ModbusControlBlock`

  Bases: `pymodbus.interfaces.Singleton`

  This is a global singleotn that controls all system information

  All activity should be logged here and all diagnostic requests should come from here.

  `Counter`
  `Delimiter`
  `Events`
  `Identity`
  `ListenOnly`
  `Mode`
  `Plus`
  `addEvent`(event)

    Adds a new event to the event log

    Parameters: | event – A new event to add to the log

  `clearEvents`()

    Clears the current list of events

  `getDiagnostic`(bit)

    This gets the value in the diagnostic register

    Parameters: | bit – The bit to get
    Returns: | The current value of the requested bit

  `getDiagnosticRegister`()

    This gets the entire diagnostic register

    Returns: | The diagnostic register collection

  `getEvents`()

    Returns an encoded collection of the event log.

    Returns: | The encoded events packet

  `reset`()

    This clears all of the system counters and the diagnostic register

  `setDiagnostic`(mapping)

    This sets the value in the diagnostic register

    Parameters: | mapping – Dictionary of key:value pairs to set

## pymodbus.diag_message module

### Diagnostic Record Read/Write

These need to be tied into a the current server context or linked to the appropriate data

class `pymodbus.diag_message.``DiagnosticStatusRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This is a base class for all of the diagnostic request functions

  `decode`(data)

    Base decoder for a diagnostic request

    Parameters: | data – The data to decode into the function code

  `encode`()

    Base encoder for a diagnostic response we encode the data set in self.message

    Returns: | The encoded packet

  `function_code` = 8
  `get_response_pdu_size`()

    Func_code (1 byte) + Sub function code (2 byte) + Data (2 * N bytes) :return:

class `pymodbus.diag_message.``DiagnosticStatusResponse`(**kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  This is a base class for all of the diagnostic response functions

  It works by performing all of the encoding and decoding of variable data and lets the higher classes define what extra data to append and how to execute a request

  `decode`(data)

    Base decoder for a diagnostic response

    Parameters: | data – The data to decode into the function code

  `encode`()

    Base encoder for a diagnostic response we encode the data set in self.message

    Returns: | The encoded packet

  `function_code` = 8

class `pymodbus.diag_message.``ReturnQueryDataRequest`(message=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusRequest`

  The data passed in the request data field is to be returned (looped back) in the response. The entire response message should be identical to the request.

  `execute`(*args)

    Executes the loopback request (builds the response)

    Returns: | The populated loopback response message

  `sub_function_code` = 0

class `pymodbus.diag_message.``ReturnQueryDataResponse`(message=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusResponse`

  The data passed in the request data field is to be returned (looped back) in the response. The entire response message should be identical to the request.

  `sub_function_code` = 0

class `pymodbus.diag_message.``RestartCommunicationsOptionRequest`(toggle=False, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusRequest`

  The remote device serial line port must be initialized and restarted, and all of its communications event counters are cleared. If the port is currently in Listen Only Mode, no response is returned. This function is the only one that brings the port out of Listen Only Mode. If the port is not currently in Listen Only Mode, a normal response is returned. This occurs before the restart is executed.

  `execute`(*args)

    Clear event log and restart

    Returns: | The initialized response message

  `sub_function_code` = 1

class `pymodbus.diag_message.``RestartCommunicationsOptionResponse`(toggle=False, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusResponse`

  The remote device serial line port must be initialized and restarted, and all of its communications event counters are cleared. If the port is currently in Listen Only Mode, no response is returned. This function is the only one that brings the port out of Listen Only Mode. If the port is not currently in Listen Only Mode, a normal response is returned. This occurs before the restart is executed.

  `sub_function_code` = 1

class `pymodbus.diag_message.``ReturnDiagnosticRegisterRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The contents of the remote device’s 16-bit diagnostic register are returned in the response

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 2

class `pymodbus.diag_message.``ReturnDiagnosticRegisterResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The contents of the remote device’s 16-bit diagnostic register are returned in the response

  `sub_function_code` = 2

class `pymodbus.diag_message.``ChangeAsciiInputDelimiterRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The character ‘CHAR’ passed in the request data field becomes the end of message delimiter for future messages (replacing the default LF character). This function is useful in cases of a Line Feed is not required at the end of ASCII messages.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 3

class `pymodbus.diag_message.``ChangeAsciiInputDelimiterResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The character ‘CHAR’ passed in the request data field becomes the end of message delimiter for future messages (replacing the default LF character). This function is useful in cases of a Line Feed is not required at the end of ASCII messages.

  `sub_function_code` = 3

class `pymodbus.diag_message.``ForceListenOnlyModeRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  Forces the addressed remote device to its Listen Only Mode for MODBUS communications. This isolates it from the other devices on the network, allowing them to continue communicating without interruption from the addressed remote device. No response is returned.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 4

class `pymodbus.diag_message.``ForceListenOnlyModeResponse`(**kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusResponse`

  Forces the addressed remote device to its Listen Only Mode for MODBUS communications. This isolates it from the other devices on the network, allowing them to continue communicating without interruption from the addressed remote device. No response is returned.

  This does not send a response

  `should_respond` = False
  `sub_function_code` = 4

class `pymodbus.diag_message.``ClearCountersRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The goal is to clear ll counters and the diagnostic register. Also, counters are cleared upon power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 10

class `pymodbus.diag_message.``ClearCountersResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The goal is to clear ll counters and the diagnostic register. Also, counters are cleared upon power-up

  `sub_function_code` = 10

class `pymodbus.diag_message.``ReturnBusMessageCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages that the remote device has detected on the communications systems since its last restart, clear counters operation, or power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 11

class `pymodbus.diag_message.``ReturnBusMessageCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages that the remote device has detected on the communications systems since its last restart, clear counters operation, or power-up

  `sub_function_code` = 11

class `pymodbus.diag_message.``ReturnBusCommunicationErrorCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of CRC errors encountered by the remote device since its last restart, clear counter operation, or power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 12

class `pymodbus.diag_message.``ReturnBusCommunicationErrorCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of CRC errors encountered by the remote device since its last restart, clear counter operation, or power-up

  `sub_function_code` = 12

class `pymodbus.diag_message.``ReturnBusExceptionErrorCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of modbus exception responses returned by the remote device since its last restart, clear counters operation, or power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 13

class `pymodbus.diag_message.``ReturnBusExceptionErrorCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of modbus exception responses returned by the remote device since its last restart, clear counters operation, or power-up

  `sub_function_code` = 13

class `pymodbus.diag_message.``ReturnSlaveMessageCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages addressed to the remote device, or broadcast, that the remote device has processed since its last restart, clear counters operation, or power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 14

class `pymodbus.diag_message.``ReturnSlaveMessageCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the remote device, or broadcast, that the remote device has processed since its last restart, clear counters operation, or power-up

  `sub_function_code` = 14

class `pymodbus.diag_message.``ReturnSlaveNoResponseCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages addressed to the remote device, or broadcast, that the remote device has processed since its last restart, clear counters operation, or power-up

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 15

class `pymodbus.diag_message.``ReturnSlaveNoReponseCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the remote device, or broadcast, that the remote device has processed since its last restart, clear counters operation, or power-up

  `sub_function_code` = 15

class `pymodbus.diag_message.``ReturnSlaveNAKCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages addressed to the remote device for which it returned a Negative Acknowledge (NAK) exception response, since its last restart, clear counters operation, or power-up. Exception responses are described and listed in section 7 .

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 16

class `pymodbus.diag_message.``ReturnSlaveNAKCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the remote device for which it returned a Negative Acknowledge (NAK) exception response, since its last restart, clear counters operation, or power-up. Exception responses are described and listed in section 7.

  `sub_function_code` = 16

class `pymodbus.diag_message.``ReturnSlaveBusyCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages addressed to the remote device for which it returned a Slave Device Busy exception response, since its last restart, clear counters operation, or power-up.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 17

class `pymodbus.diag_message.``ReturnSlaveBusyCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the remote device for which it returned a Slave Device Busy exception response, since its last restart, clear counters operation, or power-up.

  `sub_function_code` = 17

class `pymodbus.diag_message.``ReturnSlaveBusCharacterOverrunCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  The response data field returns the quantity of messages addressed to the remote device that it could not handle due to a character overrun condition, since its last restart, clear counters operation, or power-up. A character overrun is caused by data characters arriving at the port faster than they can be stored, or by the loss of a character due to a hardware malfunction.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 18

class `pymodbus.diag_message.``ReturnSlaveBusCharacterOverrunCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the remote device that it could not handle due to a character overrun condition, since its last restart, clear counters operation, or power-up. A character overrun is caused by data characters arriving at the port faster than they can be stored, or by the loss of a character due to a hardware malfunction.

  `sub_function_code` = 18

class `pymodbus.diag_message.``ReturnIopOverrunCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  An IOP overrun is caused by data characters arriving at the port faster than they can be stored, or by the loss of a character due to a hardware malfunction. This function is specific to the 884.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 19

class `pymodbus.diag_message.``ReturnIopOverrunCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  The response data field returns the quantity of messages addressed to the slave that it could not handle due to an 884 IOP overrun condition, since its last restart, clear counters operation, or power-up.

  `sub_function_code` = 19

class `pymodbus.diag_message.``ClearOverrunCountRequest`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  Clears the overrun error counter and reset the error flag

  An error flag should be cleared, but nothing else in the specification mentions is, so it is ignored.

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `sub_function_code` = 20

class `pymodbus.diag_message.``ClearOverrunCountResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  Clears the overrun error counter and reset the error flag

  `sub_function_code` = 20

class `pymodbus.diag_message.``GetClearModbusPlusRequest`(**kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleRequest`

  In addition to the Function code (08) and Subfunction code (00 15 hex) in the query, a two-byte Operation field is used to specify either a ‘Get Statistics’ or a ‘Clear Statistics’ operation. The two operations are exclusive - the ‘Get’ operation cannot clear the statistics, and the ‘Clear’ operation does not return statistics prior to clearing them. Statistics are also cleared on power-up of the slave device.

  `encode`()

    Base encoder for a diagnostic response we encode the data set in self.message

    Returns: | The encoded packet

  `execute`(*args)

    Execute the diagnostic request on the given device

    Returns: | The initialized response message

  `get_response_pdu_size`()

    Returns a series of 54 16-bit words (108 bytes) in the data field of the response (this function differs from the usual two-byte length of the data field). The data contains the statistics for the Modbus Plus peer processor in the slave device. Func_code (1 byte) + Sub function code (2 byte) + Operation (2 byte) + Data (108 bytes) :return:

  `sub_function_code` = 21

class `pymodbus.diag_message.``GetClearModbusPlusResponse`(data=0, **kwargs)

  Bases: `pymodbus.diag_message.DiagnosticStatusSimpleResponse`

  Returns a series of 54 16-bit words (108 bytes) in the data field of the response (this function differs from the usual two-byte length of the data field). The data contains the statistics for the Modbus Plus peer processor in the slave device.

  `sub_function_code` = 21

## pymodbus.events module

### Modbus Remote Events

An event byte returned by the Get Communications Event Log function can be any one of four types. The type is defined by bit 7 (the high-order bit) in each byte. It may be further defined by bit 6.

class `pymodbus.events.``CommunicationRestartEvent`

  Bases: `pymodbus.events.ModbusEvent`

  Remote device Initiated Communication Restart

  The remote device stores this type of event byte when its communications port is restarted. The remote device can be restarted by the Diagnostics function (code 08), with sub-function Restart Communications Option (code 00 01).

  That function also places the remote device into a ‘Continue on Error’ or ‘Stop on Error’ mode. If the remote device is placed into ‘Continue on Error’ mode, the event byte is added to the existing event log. If the remote device is placed into ‘Stop on Error’ mode, the byte is added to the log and the rest of the log is cleared to zeros.

  The event is defined by a content of zero.

  `decode`(event)

    Decodes the event message to its status bits

    Parameters: | event – The event to decode

  `encode`()

    Encodes the status bits to an event message

    Returns: | The encoded event message

  `value` = 0

class `pymodbus.events.``EnteredListenModeEvent`

  Bases: `pymodbus.events.ModbusEvent`

  Remote device Entered Listen Only Mode

  The remote device stores this type of event byte when it enters the Listen Only Mode. The event is defined by a content of 04 hex.

  `decode`(event)

    Decodes the event message to its status bits

    Parameters: | event – The event to decode

  `encode`()

    Encodes the status bits to an event message

    Returns: | The encoded event message

  `value` = 4

class `pymodbus.events.``ModbusEvent`

  Bases: `object`

  `decode`(event)

    Decodes the event message to its status bits

    Parameters: | event – The event to decode

  `encode`()

    Encodes the status bits to an event message

    Returns: | The encoded event message

class `pymodbus.events.``RemoteReceiveEvent`(**kwargs)

  Bases: `pymodbus.events.ModbusEvent`

  Remote device MODBUS Receive Event

  The remote device stores this type of event byte when a query message is received. It is stored before the remote device processes the message. This event is defined by bit 7 set to logic ‘1’. The other bits will be set to a logic ‘1’ if the corresponding condition is TRUE. The bit layout is:

      Bit Contents
      ----------------------------------
      0   Not Used
      2   Not Used
      3   Not Used
      4   Character Overrun
      5   Currently in Listen Only Mode
      6   Broadcast Receive
      7   1

  `decode`(event)

    Decodes the event message to its status bits

    Parameters: | event – The event to decode

  `encode`()

    Encodes the status bits to an event message

    Returns: | The encoded event message

class `pymodbus.events.``RemoteSendEvent`(**kwargs)

  Bases: `pymodbus.events.ModbusEvent`

  Remote device MODBUS Send Event

  The remote device stores this type of event byte when it finishes processing a request message. It is stored if the remote device returned a normal or exception response, or no response.

  This event is defined by bit 7 set to a logic ‘0’, with bit 6 set to a ‘1’. The other bits will be set to a logic ‘1’ if the corresponding condition is TRUE. The bit layout is:

      Bit Contents
      -----------------------------------------------------------
      0   Read Exception Sent (Exception Codes 1-3)
      1   Slave Abort Exception Sent (Exception Code 4)
      2   Slave Busy Exception Sent (Exception Codes 5-6)
      3   Slave Program NAK Exception Sent (Exception Code 7)
      4   Write Timeout Error Occurred
      5   Currently in Listen Only Mode
      6   1
      7   0

  `decode`(event)

    Decodes the event message to its status bits

    Parameters: | event – The event to decode

  `encode`()

    Encodes the status bits to an event message

    Returns: | The encoded event message

## pymodbus.exceptions module

### Pymodbus Exceptions

Custom exceptions to be used in the Modbus code.

exception `pymodbus.exceptions.``ModbusException`(string)

  Bases: `Exception`

  Base modbus exception

  `isError`()

    Error

exception `pymodbus.exceptions.``ModbusIOException`(string='', function_code=None)

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from data i/o

exception `pymodbus.exceptions.``ParameterException`(string='')

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from invalid parameter

exception `pymodbus.exceptions.``NotImplementedException`(string='')

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from not implemented function

exception `pymodbus.exceptions.``ConnectionException`(string='')

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from a bad connection

exception `pymodbus.exceptions.``NoSuchSlaveException`(string='')

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from making a request to a slave that does not exist

exception `pymodbus.exceptions.``InvalidMessageReceivedException`(string='')

  Bases: `pymodbus.exceptions.ModbusException`

  Error resulting from invalid response received or decoded

## pymodbus.factory module

### Modbus Request/Response Decoder Factories

The following factories make it easy to decode request/response messages. To add a new request/response pair to be decodeable by the library, simply add them to the respective function lookup table (order doesn’t matter, but it does help keep things organized).

Regardless of how many functions are added to the lookup, O(1) behavior is kept as a result of a pre-computed lookup dictionary.

class `pymodbus.factory.``ServerDecoder`

  Bases: `pymodbus.interfaces.IModbusDecoder`

  Request Message Factory (Server)

  To add more implemented functions, simply add them to the list

  `decode`(message)

    Wrapper to decode a request packet

    Parameters: | message – The raw modbus request packet
    Returns: | The decoded modbus message or None if error

  `lookupPduClass`(function_code)

    Use function_code to determine the class of the PDU.

    Parameters: | function_code – The function code specified in a frame.
    Returns: | The class of the PDU that has a matching function_code.

class `pymodbus.factory.``ClientDecoder`

  Bases: `pymodbus.interfaces.IModbusDecoder`

  Response Message Factory (Client)

  To add more implemented functions, simply add them to the list

  `decode`(message)

    Wrapper to decode a response packet

    Parameters: | message – The raw packet to decode
    Returns: | The decoded modbus message or None if error

  `lookupPduClass`(function_code)

    Use function_code to determine the class of the PDU.

    Parameters: | function_code – The function code specified in a frame.
    Returns: | The class of the PDU that has a matching function_code.

## pymodbus.file_message module

### File Record Read/Write Messages

Currently none of these messages are implemented

class `pymodbus.file_message.``FileRecord`(**kwargs)

  Bases: `object`

  Represents a file record and its relevant data.

class `pymodbus.file_message.``ReadFileRecordRequest`(records=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to perform a file record read. All request data lengths are provided in terms of number of bytes and all record lengths are provided in terms of registers.

  A file is an organization of records. Each file contains 10000 records, addressed 0000 to 9999 decimal or 0x0000 to 0x270f. For example, record 12 is addressed as 12. The function can read multiple groups of references. The groups can be separating (non-contiguous), but the references within each group must be sequential. Each group is defined in a seperate ‘sub-request’ field that contains seven bytes:

      The reference type: 1 byte (must be 0x06)
      The file number: 2 bytes
      The starting record number within the file: 2 bytes
      The length of the record to be read: 2 bytes

  The quantity of registers to be read, combined with all other fields in the expected response, must not exceed the allowable length of the MODBUS PDU: 235 bytes.

  `decode`(data)

    Decodes the incoming request

    Parameters: | data – The data to decode into the address

  `encode`()

    Encodes the request packet

    Returns: | The byte encoded packet

  `execute`(context)

    Run a read exeception status request against the store

    Parameters: | context – The datastore to request from
    Returns: | The populated response

  `function_code` = 20

class `pymodbus.file_message.``ReadFileRecordResponse`(records=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response is a series of ‘sub-responses,’ one for each ‘sub-request.’ The byte count field is the total combined count of bytes in all ‘sub-responses.’ In addition, each ‘sub-response’ contains a field that shows its own byte count.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 20

class `pymodbus.file_message.``WriteFileRecordRequest`(records=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to perform a file record write. All request data lengths are provided in terms of number of bytes and all record lengths are provided in terms of the number of 16 bit words.

  `decode`(data)

    Decodes the incoming request

    Parameters: | data – The data to decode into the address

  `encode`()

    Encodes the request packet

    Returns: | The byte encoded packet

  `execute`(context)

    Run the write file record request against the context

    Parameters: | context – The datastore to request from
    Returns: | The populated response

  `function_code` = 21

class `pymodbus.file_message.``WriteFileRecordResponse`(records=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response is an echo of the request.

  `decode`(data)

    Decodes the incoming request

    Parameters: | data – The data to decode into the address

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 21

class `pymodbus.file_message.``ReadFifoQueueRequest`(address=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code allows to read the contents of a First-In-First-Out (FIFO) queue of register in a remote device. The function returns a count of the registers in the queue, followed by the queued data. Up to 32 registers can be read: the count, plus up to 31 queued data registers.

  The queue count register is returned first, followed by the queued data registers. The function reads the queue contents, but does not clear them.

  `decode`(data)

    Decodes the incoming request

    Parameters: | data – The data to decode into the address

  `encode`()

    Encodes the request packet

    Returns: | The byte encoded packet

  `execute`(context)

    Run a read exeception status request against the store

    Parameters: | context – The datastore to request from
    Returns: | The populated response

  `function_code` = 24

class `pymodbus.file_message.``ReadFifoQueueResponse`(values=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  In a normal response, the byte count shows the quantity of bytes to follow, including the queue count bytes and value register bytes (but not including the error check field). The queue count is the quantity of data registers in the queue (not including the count register).

  If the queue count exceeds 31, an exception response is returned with an error code of 03 (Illegal Data Value).

  classmethod `calculateRtuFrameSize`(buffer)

    Calculates the size of the message

    Parameters: | buffer – A buffer containing the data that have been received.
    Returns: | The number of bytes in the response.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 24

## pymodbus.interfaces module

### Pymodbus Interfaces

A collection of base classes that are used throughout the pymodbus library.

class `pymodbus.interfaces.``Singleton`

  Bases: `object`

  Singleton base class http://mail.python.org/pipermail/python-list/2007-July/450681.html

class `pymodbus.interfaces.``IModbusDecoder`

  Bases: `object`

  Modbus Decoder Base Class

  This interface must be implemented by a modbus message decoder factory. These factories are responsible for abstracting away converting a raw packet into a request / response message object.

  `decode`(message)

    Wrapper to decode a given packet

    Parameters: | message – The raw modbus request packet
    Returns: | The decoded modbus message or None if error

  `lookupPduClass`(function_code)

    Use function_code to determine the class of the PDU.

    Parameters: | function_code – The function code specified in a frame.
    Returns: | The class of the PDU that has a matching function_code.

class `pymodbus.interfaces.``IModbusFramer`

  Bases: `object`

  A framer strategy interface. The idea is that we abstract away all the detail about how to detect if a current message frame exists, decoding it, sending it, etc so that we can plug in a new Framer object (tcp, rtu, ascii).

  `addToFrame`(message)

    Add the next message to the frame buffer

    This should be used before the decoding while loop to add the received data to the buffer handle.

    Parameters: | message – The most recent packet

  `advanceFrame`()

    Skip over the current framed message This allows us to skip over the current message after we have processed it or determined that it contains an error. It also has to reset the current frame header handle

  `buildPacket`(message)

    Creates a ready to send modbus packet

    The raw packet is built off of a fully populated modbus request / response message.

    Parameters: | message – The request/response to send
    Returns: | The built packet

  `checkFrame`()

    Check and decode the next frame

    Returns: | True if we successful, False otherwise

  `getFrame`()

    Get the next frame from the buffer

    Returns: | The frame data or ‘’

  `isFrameReady`()

    Check if we should continue decode logic

    This is meant to be used in a while loop in the decoding phase to let the decoder know that there is still data in the buffer.

    Returns: | True if ready, False otherwise

  `populateResult`(result)

    Populates the modbus result with current frame header

    We basically copy the data back over from the current header to the result header. This may not be needed for serial messages.

    Parameters: | result – The response packet

  `processIncomingPacket`(data, callback)

    The new packet processing pattern

    This takes in a new request packet, adds it to the current packet stream, and performs framing on it. That is, checks for complete messages, and once found, will process all that exist. This handles the case when we read N + 1 or 1 / N messages at a time instead of 1.

    The processed and decoded messages are pushed to the callback function to process and send.

    Parameters:

    - data – The new packet data
    - callback – The function to send results to

class `pymodbus.interfaces.``IModbusSlaveContext`

  Bases: `object`

  Interface for a modbus slave data context

  Derived classes must implemented the following methods:
    reset(self) validate(self, fx, address, count=1) getValues(self, fx, address, count=1) setValues(self, fx, address, values)
  `decode`(fx)

    Converts the function code to the datastore to

    Parameters: | fx – The function we are working with
    Returns: | one of [d(iscretes),i(inputs),h(oliding),c(oils)

  `getValues`(fx, address, count=1)

    Get count values from datastore

    Parameters:

    - fx – The function we are working with
    - address – The starting address
    - count – The number of values to retrieve

    Returns: | The requested values from a:a+c

  `reset`()

    Resets all the datastores to their default values

  `setValues`(fx, address, values)

    Sets the datastore with the supplied values

    Parameters:

    - fx – The function we are working with
    - address – The starting address
    - values – The new values to be set

  `validate`(fx, address, count=1)

    Validates the request to make sure it is in range

    Parameters:

    - fx – The function we are working with
    - address – The starting address
    - count – The number of values to test

    Returns: | True if the request in within range, False otherwise

class `pymodbus.interfaces.``IPayloadBuilder`

  Bases: `object`

  This is an interface to a class that can build a payload for a modbus register write command. It should abstract the codec for encoding data to the required format (bcd, binary, char, etc).

  `build`()

    Return the payload buffer as a list

    This list is two bytes per element and can thus be treated as a list of registers.

    Returns: | The payload buffer as a list

## pymodbus.mei_message module

### Encapsulated Interface (MEI) Transport Messages

class `pymodbus.mei_message.``ReadDeviceInformationRequest`(read_code=None, object_id=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code allows reading the identification and additional information relative to the physical and functional description of a remote device, only.

  The Read Device Identification interface is modeled as an address space composed of a set of addressable data elements. The data elements are called objects and an object Id identifies them.

  `decode`(data)

    Decodes data part of the message.

    Parameters: | data – The incoming data

  `encode`()

    Encodes the request packet

    Returns: | The byte encoded packet

  `execute`(context)

    Run a read exeception status request against the store

    Parameters: | context – The datastore to request from
    Returns: | The populated response

  `function_code` = 43
  `sub_function_code` = 14

class `pymodbus.mei_message.``ReadDeviceInformationResponse`(read_code=None, information=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  classmethod `calculateRtuFrameSize`(buffer)

    Calculates the size of the message

    Parameters: | buffer – A buffer containing the data that have been received.
    Returns: | The number of bytes in the response.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 43
  `sub_function_code` = 14

## pymodbus.other_message module

Diagnostic record read/write

Currently not all implemented

class `pymodbus.other_message.``ReadExceptionStatusRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to read the contents of eight Exception Status outputs in a remote device. The function provides a simple method for accessing this information, because the Exception Output references are known (no output reference is needed in the function).

  `decode`(data)

    Decodes data part of the message.

    Parameters: | data – The incoming data

  `encode`()

    Encodes the message

  `execute`(context=None)

    Run a read exeception status request against the store

    Returns: | The populated response

  `function_code` = 7

class `pymodbus.other_message.``ReadExceptionStatusResponse`(status=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response contains the status of the eight Exception Status outputs. The outputs are packed into one data byte, with one bit per output. The status of the lowest output reference is contained in the least significant bit of the byte. The contents of the eight Exception Status outputs are device specific.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 7

class `pymodbus.other_message.``GetCommEventCounterRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to get a status word and an event count from the remote device’s communication event counter.

  By fetching the current count before and after a series of messages, a client can determine whether the messages were handled normally by the remote device.

  The device’s event counter is incremented once for each successful message completion. It is not incremented for exception responses, poll commands, or fetch event counter commands.

  The event counter can be reset by means of the Diagnostics function (code 08), with a subfunction of Restart Communications Option (code 00 01) or Clear Counters and Diagnostic Register (code 00 0A).

  `decode`(data)

    Decodes data part of the message.

    Parameters: | data – The incoming data

  `encode`()

    Encodes the message

  `execute`(context=None)

    Run a read exeception status request against the store

    Returns: | The populated response

  `function_code` = 11

class `pymodbus.other_message.``GetCommEventCounterResponse`(count=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response contains a two-byte status word, and a two-byte event count. The status word will be all ones (FF FF hex) if a previously-issued program command is still being processed by the remote device (a busy condition exists). Otherwise, the status word will be all zeros.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 11

class `pymodbus.other_message.``GetCommEventLogRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to get a status word, event count, message count, and a field of event bytes from the remote device.

  The status word and event counts are identical to that returned by the Get Communications Event Counter function (11, 0B hex).

  The message counter contains the quantity of messages processed by the remote device since its last restart, clear counters operation, or power-up. This count is identical to that returned by the Diagnostic function (code 08), sub-function Return Bus Message Count (code 11, 0B hex).

  The event bytes field contains 0-64 bytes, with each byte corresponding to the status of one MODBUS send or receive operation for the remote device. The remote device enters the events into the field in chronological order. Byte 0 is the most recent event. Each new byte flushes the oldest byte from the field.

  `decode`(data)

    Decodes data part of the message.

    Parameters: | data – The incoming data

  `encode`()

    Encodes the message

  `execute`(context=None)

    Run a read exeception status request against the store

    Returns: | The populated response

  `function_code` = 12

class `pymodbus.other_message.``GetCommEventLogResponse`(**kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response contains a two-byte status word field, a two-byte event count field, a two-byte message count field, and a field containing 0-64 bytes of events. A byte count field defines the total length of the data in these four field

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 12

class `pymodbus.other_message.``ReportSlaveIdRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to read the description of the type, the current status, and other information specific to a remote device.

  `decode`(data)

    Decodes data part of the message.

    Parameters: | data – The incoming data

  `encode`()

    Encodes the message

  `execute`(context=None)

    Run a read exeception status request against the store

    Returns: | The populated response

  `function_code` = 17

class `pymodbus.other_message.``ReportSlaveIdResponse`(identifier=b'x00', status=True, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The format of a normal response is shown in the following example. The data contents are specific to each type of device.

  `decode`(data)

    Decodes a the response

    Since the identifier is device dependent, we just return the raw value that a user can decode to whatever it should be.

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 17

## pymodbus.payload module

### Modbus Payload Builders

A collection of utilities for building and decoding modbus messages payloads.

class `pymodbus.payload.``BinaryPayloadBuilder`(payload=None, byteorder='<', wordorder='>', repack=False)

  Bases: `pymodbus.interfaces.IPayloadBuilder`

  A utility that helps build payload messages to be written with the various modbus messages. It really is just a simple wrapper around the struct module, however it saves time looking up the format strings. What follows is a simple example:

      builder = BinaryPayloadBuilder(byteorder=Endian.Little)
      builder.add_8bit_uint(1)
      builder.add_16bit_uint(2)
      payload = builder.build()

  `add_16bit_int`(value)

    Adds a 16 bit signed int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_16bit_uint`(value)

    Adds a 16 bit unsigned int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_32bit_float`(value)

    Adds a 32 bit float to the buffer

    Parameters: | value – The value to add to the buffer

  `add_32bit_int`(value)

    Adds a 32 bit signed int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_32bit_uint`(value)

    Adds a 32 bit unsigned int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_64bit_float`(value)

    Adds a 64 bit float(double) to the buffer

    Parameters: | value – The value to add to the buffer

  `add_64bit_int`(value)

    Adds a 64 bit signed int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_64bit_uint`(value)

    Adds a 64 bit unsigned int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_8bit_int`(value)

    Adds a 8 bit signed int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_8bit_uint`(value)

    Adds a 8 bit unsigned int to the buffer

    Parameters: | value – The value to add to the buffer

  `add_bits`(values)

    Adds a collection of bits to be encoded

    If these are less than a multiple of eight, they will be left padded with 0 bits to make it so.

    Parameters: | value – The value to add to the buffer

  `add_string`(value)

    Adds a string to the buffer

    Parameters: | value – The value to add to the buffer

  `build`()

    Return the payload buffer as a list

    This list is two bytes per element and can thus be treated as a list of registers.

    Returns: | The payload buffer as a list

  `reset`()

    Reset the payload buffer

  `to_coils`()

    Convert the payload buffer into a coil layout that can be used as a context block.

    Returns: | The coil layout to use as a block

  `to_registers`()

    Convert the payload buffer into a register layout that can be used as a context block.

    Returns: | The register layout to use as a block

  `to_string`()

    Return the payload buffer as a string

    Returns: | The payload buffer as a string

class `pymodbus.payload.``BinaryPayloadDecoder`(payload, byteorder='<', wordorder='>')

  Bases: `object`

  A utility that helps decode payload messages from a modbus reponse message. It really is just a simple wrapper around the struct module, however it saves time looking up the format strings. What follows is a simple example:

      decoder = BinaryPayloadDecoder(payload)
      first   = decoder.decode_8bit_uint()
      second  = decoder.decode_16bit_uint()

  `decode_16bit_int`()

    Decodes a 16 bit signed int from the buffer

  `decode_16bit_uint`()

    Decodes a 16 bit unsigned int from the buffer

  `decode_32bit_float`()

    Decodes a 32 bit float from the buffer

  `decode_32bit_int`()

    Decodes a 32 bit signed int from the buffer

  `decode_32bit_uint`()

    Decodes a 32 bit unsigned int from the buffer

  `decode_64bit_float`()

    Decodes a 64 bit float(double) from the buffer

  `decode_64bit_int`()

    Decodes a 64 bit signed int from the buffer

  `decode_64bit_uint`()

    Decodes a 64 bit unsigned int from the buffer

  `decode_8bit_int`()

    Decodes a 8 bit signed int from the buffer

  `decode_8bit_uint`()

    Decodes a 8 bit unsigned int from the buffer

  `decode_bits`()

    Decodes a byte worth of bits from the buffer

  `decode_string`(size=1)

    Decodes a string from the buffer

    Parameters: | size – The size of the string to decode

  classmethod `fromCoils`(coils, byteorder='<')

    Initialize a payload decoder with the result of reading a collection of coils from a modbus device.

    The coils are treated as a list of bit(boolean) values.

    Parameters:

    - coils – The coil results to initialize with
    - byteorder – The endianess of the payload

    Returns: | An initialized PayloadDecoder

  classmethod `fromRegisters`(registers, byteorder='<', wordorder='>')

    Initialize a payload decoder with the result of reading a collection of registers from a modbus device.

    The registers are treated as a list of 2 byte values. We have to do this because of how the data has already been decoded by the rest of the library.

    Parameters:

    - registers – The register results to initialize with
    - byteorder – The Byte order of each word
    - wordorder – The endianess of the word (when wordcount is >= 2)

    Returns: | An initialized PayloadDecoder

  `reset`()

    Reset the decoder pointer back to the start

  `skip_bytes`(nbytes)

    Skip n bytes in the buffer

    Parameters: | nbytes – The number of bytes to skip

## pymodbus.pdu module

Contains base classes for modbus request/response/error packets

class `pymodbus.pdu.``ModbusRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusPDU`

  Base class for a modbus request PDU

  `doException`(exception)

    Builds an error response based on the function

    Parameters: | exception – The exception to return
    Raises: | An exception response

class `pymodbus.pdu.``ModbusResponse`(**kwargs)

  Bases: `pymodbus.pdu.ModbusPDU`

  Base class for a modbus response PDU

  `should_respond`

    A flag that indicates if this response returns a result back to the client issuing the request

  `_rtu_frame_size`

    Indicates the size of the modbus rtu response used for calculating how much to read.

  `isError`()

    Checks if the error is a success or failure

  `should_respond` = True

class `pymodbus.pdu.``ModbusExceptions`

  Bases: `pymodbus.interfaces.Singleton`

  An enumeration of the valid modbus exceptions

  `Acknowledge` = 5
  `GatewayNoResponse` = 11
  `GatewayPathUnavailable` = 10
  `IllegalAddress` = 2
  `IllegalFunction` = 1
  `IllegalValue` = 3
  `MemoryParityError` = 8
  `SlaveBusy` = 6
  `SlaveFailure` = 4
  classmethod `decode`(code)

    Given an error code, translate it to a string error name.

    Parameters: | code – The code number to translate

class `pymodbus.pdu.``ExceptionResponse`(function_code, exception_code=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  Base class for a modbus exception PDU

  `ExceptionOffset` = 128
  `decode`(data)

    Decodes a modbus exception response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes a modbus exception response

    Returns: | The encoded exception packet

class `pymodbus.pdu.``IllegalFunctionRequest`(function_code, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  Defines the Modbus slave exception type ‘Illegal Function’ This exception code is returned if the slave:

      - does not implement the function code **or**
      - is not in a state that allows it to process the function

  `ErrorCode` = 1
  `decode`(data)

    This is here so this failure will run correctly

    Parameters: | data – Not used

  `execute`(context)

    Builds an illegal function request error response

    Parameters: | context – The current context for the message
    Returns: | The error response packet

## pymodbus.register_read_message module

### Register Reading Request/Response

class `pymodbus.register_read_message.``ReadHoldingRegistersRequest`(address=None, count=None, **kwargs)

  Bases: `pymodbus.register_read_message.ReadRegistersRequestBase`

  This function code is used to read the contents of a contiguous block of holding registers in a remote device. The Request PDU specifies the starting register address and the number of registers. In the PDU Registers are addressed starting at zero. Therefore registers numbered 1-16 are addressed as 0-15.

  `execute`(context)

    Run a read holding request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | An initialized response, exception message otherwise

  `function_code` = 3

class `pymodbus.register_read_message.``ReadHoldingRegistersResponse`(values=None, **kwargs)

  Bases: `pymodbus.register_read_message.ReadRegistersResponseBase`

  This function code is used to read the contents of a contiguous block of holding registers in a remote device. The Request PDU specifies the starting register address and the number of registers. In the PDU Registers are addressed starting at zero. Therefore registers numbered 1-16 are addressed as 0-15.

  `function_code` = 3

class `pymodbus.register_read_message.``ReadInputRegistersRequest`(address=None, count=None, **kwargs)

  Bases: `pymodbus.register_read_message.ReadRegistersRequestBase`

  This function code is used to read from 1 to approx. 125 contiguous input registers in a remote device. The Request PDU specifies the starting register address and the number of registers. In the PDU Registers are addressed starting at zero. Therefore input registers numbered 1-16 are addressed as 0-15.

  `execute`(context)

    Run a read input request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | An initialized response, exception message otherwise

  `function_code` = 4

class `pymodbus.register_read_message.``ReadInputRegistersResponse`(values=None, **kwargs)

  Bases: `pymodbus.register_read_message.ReadRegistersResponseBase`

  This function code is used to read from 1 to approx. 125 contiguous input registers in a remote device. The Request PDU specifies the starting register address and the number of registers. In the PDU Registers are addressed starting at zero. Therefore input registers numbered 1-16 are addressed as 0-15.

  `function_code` = 4

class `pymodbus.register_read_message.``ReadWriteMultipleRegistersRequest`(**kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code performs a combination of one read operation and one write operation in a single MODBUS transaction. The write operation is performed before the read.

  Holding registers are addressed starting at zero. Therefore holding registers 1-16 are addressed in the PDU as 0-15.

  The request specifies the starting address and number of holding registers to be read as well as the starting address, number of holding registers, and the data to be written. The byte count specifies the number of bytes to follow in the write data field.”

  `decode`(data)

    Decode the register request packet

    Parameters: | data – The request to decode

  `encode`()

    Encodes the request packet

    Returns: | The encoded packet

  `execute`(context)

    Run a write single register request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | An initialized response, exception message otherwise

  `function_code` = 23
  `get_response_pdu_size`()

    Func_code (1 byte) + Byte Count(1 byte) + 2 * Quantity of Coils (n Bytes) :return:

class `pymodbus.register_read_message.``ReadWriteMultipleRegistersResponse`(values=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response contains the data from the group of registers that were read. The byte count field specifies the quantity of bytes to follow in the read data field.

  `decode`(data)

    Decode the register response packet

    Parameters: | data – The response to decode

  `encode`()

    Encodes the response packet

    Returns: | The encoded packet

  `function_code` = 23

## pymodbus.register_write_message module

### Register Writing Request/Response Messages

class `pymodbus.register_write_message.``WriteSingleRegisterRequest`(address=None, value=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to write a single holding register in a remote device.

  The Request PDU specifies the address of the register to be written. Registers are addressed starting at zero. Therefore register numbered 1 is addressed as 0.

  `decode`(data)

    Decode a write single register packet packet request

    Parameters: | data – The request to decode

  `encode`()

    Encode a write single register packet packet request

    Returns: | The encoded packet

  `execute`(context)

    Run a write single register request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | An initialized response, exception message otherwise

  `function_code` = 6
  `get_response_pdu_size`()

    Func_code (1 byte) + Register Address(2 byte) + Register Value (2 bytes) :return:

class `pymodbus.register_write_message.``WriteSingleRegisterResponse`(address=None, value=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response is an echo of the request, returned after the register contents have been written.

  `decode`(data)

    Decode a write single register packet packet request

    Parameters: | data – The request to decode

  `encode`()

    Encode a write single register packet packet request

    Returns: | The encoded packet

  `function_code` = 6

class `pymodbus.register_write_message.``WriteMultipleRegistersRequest`(address=None, values=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to write a block of contiguous registers (1 to approx. 120 registers) in a remote device.

  The requested written values are specified in the request data field. Data is packed as two bytes per register.

  `decode`(data)

    Decode a write single register packet packet request

    Parameters: | data – The request to decode

  `encode`()

    Encode a write single register packet packet request

    Returns: | The encoded packet

  `execute`(context)

    Run a write single register request against a datastore

    Parameters: | context – The datastore to request from
    Returns: | An initialized response, exception message otherwise

  `function_code` = 16
  `get_response_pdu_size`()

    Func_code (1 byte) + Starting Address (2 byte) + Quantity of Reggisters (2 Bytes) :return:

class `pymodbus.register_write_message.``WriteMultipleRegistersResponse`(address=None, count=None, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  “The normal response returns the function code, starting address, and quantity of registers written.

  `decode`(data)

    Decode a write single register packet packet request

    Parameters: | data – The request to decode

  `encode`()

    Encode a write single register packet packet request

    Returns: | The encoded packet

  `function_code` = 16

class `pymodbus.register_write_message.``MaskWriteRegisterRequest`(address=0, and_mask=65535, or_mask=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusRequest`

  This function code is used to modify the contents of a specified holding register using a combination of an AND mask, an OR mask, and the register’s current contents. The function can be used to set or clear individual bits in the register.

  `decode`(data)

    Decodes the incoming request

    Parameters: | data – The data to decode into the address

  `encode`()

    Encodes the request packet

    Returns: | The byte encoded packet

  `execute`(context)

    Run a mask write register request against the store

    Parameters: | context – The datastore to request from
    Returns: | The populated response

  `function_code` = 22

class `pymodbus.register_write_message.``MaskWriteRegisterResponse`(address=0, and_mask=65535, or_mask=0, **kwargs)

  Bases: `pymodbus.pdu.ModbusResponse`

  The normal response is an echo of the request. The response is returned after the register has been written.

  `decode`(data)

    Decodes a the response

    Parameters: | data – The packet data to decode

  `encode`()

    Encodes the response

    Returns: | The byte encoded message

  `function_code` = 22

## pymodbus.transaction module

Collection of transaction based abstractions

class `pymodbus.transaction.``FifoTransactionManager`(client, **kwargs)

  Bases: `pymodbus.transaction.ModbusTransactionManager`

  Impelements a transaction for a manager where the results are returned in a FIFO manner.

  `addTransaction`(request, tid=None)

    Adds a transaction to the handler

    This holds the requets in case it needs to be resent. After being sent, the request is removed.

    Parameters:

    - request – The request to hold on to
    - tid – The overloaded transaction id to use

  `delTransaction`(tid)

    Removes a transaction matching the referenced tid

    Parameters: | tid – The transaction to remove

  `getTransaction`(tid)

    Returns a transaction matching the referenced tid

    If the transaction does not exist, None is returned

    Parameters: | tid – The transaction to retrieve

class `pymodbus.transaction.``DictTransactionManager`(client, **kwargs)

  Bases: `pymodbus.transaction.ModbusTransactionManager`

  Impelements a transaction for a manager where the results are keyed based on the supplied transaction id.

  `addTransaction`(request, tid=None)

    Adds a transaction to the handler

    This holds the requets in case it needs to be resent. After being sent, the request is removed.

    Parameters:

    - request – The request to hold on to
    - tid – The overloaded transaction id to use

  `delTransaction`(tid)

    Removes a transaction matching the referenced tid

    Parameters: | tid – The transaction to remove

  `getTransaction`(tid)

    Returns a transaction matching the referenced tid

    If the transaction does not exist, None is returned

    Parameters: | tid – The transaction to retrieve

class `pymodbus.transaction.``ModbusSocketFramer`(decoder, client=None)

  Bases: `pymodbus.framer.ModbusFramer`

  Modbus Socket Frame controller

  Before each modbus TCP message is an MBAP header which is used as a message frame. It allows us to easily separate messages as follows:

      [         MBAP Header         ] [ Function Code] [ Data ]         [ tid ][ pid ][ length ][ uid ]
        2b     2b     2b        1b           1b           Nb

      while len(message) > 0:
          tid, pid, length`, uid = struct.unpack(">HHHB", message)
          request = message[0:7 + length - 1`]
          message = [7 + length - 1:]

      * length = uid + function code + data
      * The -1 is to account for the uid byte

  `addToFrame`(message)

    Adds new packet data to the current frame buffer

    Parameters: | message – The most recent packet

  `advanceFrame`()

    Skip over the current framed message This allows us to skip over the current message after we have processed it or determined that it contains an error. It also has to reset the current frame header handle

  `buildPacket`(message)

    Creates a ready to send modbus packet

    Parameters: | message – The populated request/response to send

  `checkFrame`()

    Check and decode the next frame Return true if we were successful

  `decode_data`(data)
  `getFrame`()

    Return the next frame from the buffered data

    Returns: | The next full frame buffer

  `getRawFrame`()

    Returns the complete buffer

  `isFrameReady`()

    Check if we should continue decode logic This is meant to be used in a while loop in the decoding phase to let the decoder factory know that there is still data in the buffer.

    Returns: | True if ready, False otherwise

  `populateResult`(result)

    Populates the modbus result with the transport specific header information (pid, tid, uid, checksum, etc)

    Parameters: | result – The response packet

  `processIncomingPacket`(data, callback, unit, **kwargs)

    The new packet processing pattern

    This takes in a new request packet, adds it to the current packet stream, and performs framing on it. That is, checks for complete messages, and once found, will process all that exist. This handles the case when we read N + 1 or 1 // N messages at a time instead of 1.

    The processed and decoded messages are pushed to the callback function to process and send.

    Parameters:

    - data – The new packet data
    - callback – The function to send results to
    - unit – Process if unit id matches, ignore otherwise (could be a list of unit ids (server) or single unit id(client/server)
    - single – True or False (If True, ignore unit address validation)

    Returns: |

  `resetFrame`()

    Reset the entire message frame. This allows us to skip ovver errors that may be in the stream. It is hard to know if we are simply out of sync or if there is an error in the stream as we have no way to check the start or end of the message (python just doesn’t have the resolution to check for millisecond delays).

class `pymodbus.transaction.``ModbusRtuFramer`(decoder, client=None)

  Bases: `pymodbus.framer.ModbusFramer`

  Modbus RTU Frame controller:

      [ Start Wait ] [Address ][ Function Code] [ Data ][ CRC ][  End Wait  ]
        3.5 chars     1b         1b               Nb      2b      3.5 chars

  Wait refers to the amount of time required to transmit at least x many characters. In this case it is 3.5 characters. Also, if we receive a wait of 1.5 characters at any point, we must trigger an error message. Also, it appears as though this message is little endian. The logic is simplified as the following:

      block-on-read:
          read until 3.5 delay
          check for errors
          decode

  The following table is a listing of the baud wait times for the specified baud rates:

      ------------------------------------------------------------------
       Baud  1.5c (18 bits)   3.5c (38 bits)
      ------------------------------------------------------------------
       1200   13333.3 us       31666.7 us
       4800    3333.3 us        7916.7 us
       9600    1666.7 us        3958.3 us
      19200     833.3 us        1979.2 us
      38400     416.7 us         989.6 us
      ------------------------------------------------------------------
      1 Byte = start + 8 bits + parity + stop = 11 bits
      (1/Baud)(bits) = delay seconds

  `addToFrame`(message)

    This should be used before the decoding while loop to add the received data to the buffer handle.

    Parameters: | message – The most recent packet

  `advanceFrame`()

    Skip over the current framed message This allows us to skip over the current message after we have processed it or determined that it contains an error. It also has to reset the current frame header handle

  `buildPacket`(message)

    Creates a ready to send modbus packet

    Parameters: | message – The populated request/response to send

  `checkFrame`()

    Check if the next frame is available. Return True if we were successful.

    1. Populate header
    2. Discard frame if UID does not match
  `decode_data`(data)
  `getFrame`()

    Get the next frame from the buffer

    Returns: | The frame data or ‘’

  `getRawFrame`()

    Returns the complete buffer

  `isFrameReady`()

    Check if we should continue decode logic This is meant to be used in a while loop in the decoding phase to let the decoder know that there is still data in the buffer.

    Returns: | True if ready, False otherwise

  `populateHeader`(data=None)

    Try to set the headers uid, len and crc.

    This method examines self._buffer and writes meta information into self._header. It calculates only the values for headers that are not already in the dictionary.

    Beware that this method will raise an IndexError if self._buffer is not yet long enough.

  `populateResult`(result)

    Populates the modbus result header

    The serial packets do not have any header information that is copied.

    Parameters: | result – The response packet

  `processIncomingPacket`(data, callback, unit, **kwargs)

    The new packet processing pattern

    This takes in a new request packet, adds it to the current packet stream, and performs framing on it. That is, checks for complete messages, and once found, will process all that exist. This handles the case when we read N + 1 or 1 // N messages at a time instead of 1.

    The processed and decoded messages are pushed to the callback function to process and send.

    Parameters:

    - data – The new packet data
    - callback – The function to send results to
    - unit – Process if unit id matches, ignore otherwise (could be a list of unit ids (server) or single unit id(client/server)
    - single – True or False (If True, ignore unit address validation)

  `recvPacket`(size)

    Receives packet from the bus with specified len :param size: Number of bytes to read :return:

  `resetFrame`()

    Reset the entire message frame. This allows us to skip over errors that may be in the stream. It is hard to know if we are simply out of sync or if there is an error in the stream as we have no way to check the start or end of the message (python just doesn’t have the resolution to check for millisecond delays).

  `sendPacket`(message)

    Sends packets on the bus with 3.5char delay between frames :param message: Message to be sent over the bus :return:

class `pymodbus.transaction.``ModbusAsciiFramer`(decoder, client=None)

  Bases: `pymodbus.framer.ModbusFramer`

  Modbus ASCII Frame Controller:

      [ Start ][Address ][ Function ][ Data ][ LRC ][ End ]
        1c        2c         2c         Nc     2c      2c

      * data can be 0 - 2x252 chars
      * end is '\r\n' (Carriage return line feed), however the line feed
        character can be changed via a special command
      * start is ':'

  This framer is used for serial transmission. Unlike the RTU protocol, the data in this framer is transferred in plain text ascii.

  `addToFrame`(message)

    Add the next message to the frame buffer This should be used before the decoding while loop to add the received data to the buffer handle.

    Parameters: | message – The most recent packet

  `advanceFrame`()

    Skip over the current framed message This allows us to skip over the current message after we have processed it or determined that it contains an error. It also has to reset the current frame header handle

  `buildPacket`(message)

    Creates a ready to send modbus packet Built off of a modbus request/response

    Parameters: | message – The request/response to send
    Returns: | The encoded packet

  `checkFrame`()

    Check and decode the next frame

    Returns: | True if we successful, False otherwise

  `decode_data`(data)
  `getFrame`()

    Get the next frame from the buffer

    Returns: | The frame data or ‘’

  `isFrameReady`()

    Check if we should continue decode logic This is meant to be used in a while loop in the decoding phase to let the decoder know that there is still data in the buffer.

    Returns: | True if ready, False otherwise

  `populateResult`(result)

    Populates the modbus result header

    The serial packets do not have any header information that is copied.

    Parameters: | result – The response packet

  `processIncomingPacket`(data, callback, unit, **kwargs)

    The new packet processing pattern

    This takes in a new request packet, adds it to the current packet stream, and performs framing on it. That is, checks for complete messages, and once found, will process all that exist. This handles the case when we read N + 1 or 1 // N messages at a time instead of 1.

    The processed and decoded messages are pushed to the callback function to process and send.

    Parameters:

    - data – The new packet data
    - callback – The function to send results to
    - unit – Process if unit id matches, ignore otherwise (could be a list of unit ids (server) or single unit id(client/server))
    - single – True or False (If True, ignore unit address validation)

  `resetFrame`()

    Reset the entire message frame. This allows us to skip ovver errors that may be in the stream. It is hard to know if we are simply out of sync or if there is an error in the stream as we have no way to check the start or end of the message (python just doesn’t have the resolution to check for millisecond delays).

class `pymodbus.transaction.``ModbusBinaryFramer`(decoder, client=None)

  Bases: `pymodbus.framer.ModbusFramer`

  Modbus Binary Frame Controller:

      [ Start ][Address ][ Function ][ Data ][ CRC ][ End ]
        1b        1b         1b         Nb     2b     1b

      * data can be 0 - 2x252 chars
      * end is   '}'
      * start is '{'

  The idea here is that we implement the RTU protocol, however, instead of using timing for message delimiting, we use start and end of message characters (in this case { and }). Basically, this is a binary framer.

  The only case we have to watch out for is when a message contains the { or } characters. If we encounter these characters, we simply duplicate them. Hopefully we will not encounter those characters that often and will save a little bit of bandwitch without a real-time system.

  Protocol defined by jamod.sourceforge.net.

  `addToFrame`(message)

    Add the next message to the frame buffer This should be used before the decoding while loop to add the received data to the buffer handle.

    Parameters: | message – The most recent packet

  `advanceFrame`()

    Skip over the current framed message This allows us to skip over the current message after we have processed it or determined that it contains an error. It also has to reset the current frame header handle

  `buildPacket`(message)

    Creates a ready to send modbus packet

    Parameters: | message – The request/response to send
    Returns: | The encoded packet

  `checkFrame`()

    Check and decode the next frame

    Returns: | True if we are successful, False otherwise

  `decode_data`(data)
  `getFrame`()

    Get the next frame from the buffer

    Returns: | The frame data or ‘’

  `isFrameReady`()

    Check if we should continue decode logic This is meant to be used in a while loop in the decoding phase to let the decoder know that there is still data in the buffer.

    Returns: | True if ready, False otherwise

  `populateResult`(result)

    Populates the modbus result header

    The serial packets do not have any header information that is copied.

    Parameters: | result – The response packet

  `processIncomingPacket`(data, callback, unit, **kwargs)

    The new packet processing pattern

    This takes in a new request packet, adds it to the current packet stream, and performs framing on it. That is, checks for complete messages, and once found, will process all that exist. This handles the case when we read N + 1 or 1 // N messages at a time instead of 1.

    The processed and decoded messages are pushed to the callback function to process and send.

    Parameters:

    - data – The new packet data
    - callback – The function to send results to
    - unit – Process if unit id matches, ignore otherwise (could be a list of unit ids (server) or single unit id(client/server)
    - single – True or False (If True, ignore unit address validation)

  `resetFrame`()

    Reset the entire message frame. This allows us to skip ovver errors that may be in the stream. It is hard to know if we are simply out of sync or if there is an error in the stream as we have no way to check the start or end of the message (python just doesn’t have the resolution to check for millisecond delays).

## pymodbus.utilities module

### Modbus Utilities

A collection of utilities for packing data, unpacking data computing checksums, and decode checksums.

`pymodbus.utilities.``pack_bitstring`(bits)

  Creates a string out of an array of bits

  Parameters: | bits – A bit array

  example:

      bits   = [False, True, False, True]
      result = pack_bitstring(bits)

`pymodbus.utilities.``unpack_bitstring`(string)

  Creates bit array out of a string

  Parameters: | string – The modbus data packet to decode

  example:

      bytes  = 'bytes to decode'
      result = unpack_bitstring(bytes)

`pymodbus.utilities.``default`(value)

  Given a python object, return the default value of that object.

  Parameters: | value – The value to get the default of
  Returns: | The default value

`pymodbus.utilities.``computeCRC`(data)

  Computes a crc16 on the passed in string. For modbus, this is only used on the binary serial protocols (in this case RTU).

  The difference between modbus’s crc16 and a normal crc16 is that modbus starts the crc value out at 0xffff.

  Parameters: | data – The data to create a crc16 of
  Returns: | The calculated CRC

`pymodbus.utilities.``checkCRC`(data, check)

  Checks if the data matches the passed in CRC

  Parameters:

  - data – The data to create a crc16 of
  - check – The CRC to validate

  Returns: | True if matched, False otherwise

`pymodbus.utilities.``computeLRC`(data)

  Used to compute the longitudinal redundancy check against a string. This is only used on the serial ASCII modbus protocol. A full description of this implementation can be found in appendex B of the serial line modbus description.

  Parameters: | data – The data to apply a lrc to
  Returns: | The calculated LRC

`pymodbus.utilities.``checkLRC`(data, check)

  Checks if the passed in data matches the LRC

  Parameters:

  - data – The data to calculate
  - check – The LRC to validate

  Returns: | True if matched, False otherwise

`pymodbus.utilities.``rtuFrameSize`(data, byte_count_pos)

  Calculates the size of the frame based on the byte count.

  Parameters:

  - data – The buffer containing the frame.
  - byte_count_pos – The index of the byte count in the buffer.

  Returns: | The size of the frame.

  The structure of frames with a byte count field is always the same:

  - first, there are some header fields
  - then the byte count field
  - then as many data bytes as indicated by the byte count,
  - finally the CRC (two bytes).

  To calculate the frame size, it is therefore sufficient to extract the contents of the byte count field, add the position of this field, and finally increment the sum by three (one byte for the byte count field, two for the CRC).

## pymodbus.version module

Handle the version information here; you should only have to change the version tuple.

Since we are using twisted’s version class, we can also query the svn version as well using the local .entries file.