payload — Modbus Payload Utilities

API Documentation

Modbus Payload Builders

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

class pymodbus.payload.BinaryPayloadBuilder(payload=None, endian='<')

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(endian=Endian.Little)
builder.add_8bit_uint(1)
builder.add_16bit_uint(2)
payload = builder.build()
__init__(payload=None, endian='<')

Initialize a new instance of the payload builder

Parameters:
  • payload – Raw binary payload data to initialize with
  • endian – The endianess of the payload
__str__()

Return the payload buffer as a string

Returns:The payload buffer as a string
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_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, endian='<')

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()
__init__(payload, endian='<')

Initialize a new payload decoder

Parameters:
  • payload – The payload to decode with
  • endian – The endianess of the payload
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(klass, coils, endian='<')

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
  • endian – The endianess of the payload
Returns:

An initialized PayloadDecoder
classmethod fromRegisters(klass, registers, endian='<')

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
  • endian – The endianess of the payload
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