"""Contains base classes for modbus request/response/error packets.""" # pylint: disable=missing-type-doc import struct from pymodbus.exceptions import NotImplementedException from pymodbus.logging import Log from pymodbus.utilities import rtuFrameSize # --------------------------------------------------------------------------- # # Base PDUs # --------------------------------------------------------------------------- # class ModbusPDU: """Base class for all Modbus messages. .. attribute:: transaction_id This value is used to uniquely identify a request response pair. It can be implemented as a simple counter .. attribute:: protocol_id This is a constant set at 0 to indicate Modbus. It is put here for ease of expansion. .. attribute:: slave_id This is used to route the request to the correct child. In the TCP modbus, it is used for routing (or not used at all. However, for the serial versions, it is used to specify which child to perform the requests against. The value 0x00 represents the broadcast address (also 0xff). .. attribute:: check This is used for LRC/CRC in the serial modbus protocols .. attribute:: skip_encode This is used when the message payload has already been encoded. Generally this will occur when the PayloadBuilder is being used to create a complicated message. By setting this to True, the request will pass the currently encoded message through instead of encoding it again. """ def __init__(self, slave, transaction, protocol, skip_encode): """Initialize the base data for a modbus request. :param slave: Modbus slave slave ID """ self.transaction_id = transaction self.protocol_id = protocol self.slave_id = slave self.skip_encode = skip_encode self.check = 0x0000 def encode(self): """Encode the message. :raises: A not implemented exception """ raise NotImplementedException() def decode(self, data): """Decode data part of the message. :param data: is a string object :raises NotImplementedException: """ raise NotImplementedException() @classmethod def calculateRtuFrameSize(cls, buffer): """Calculate the size of a PDU. :param buffer: A buffer containing the data that have been received. :returns: The number of bytes in the PDU. :raises NotImplementedException: """ if hasattr(cls, "_rtu_frame_size"): return cls._rtu_frame_size if hasattr(cls, "_rtu_byte_count_pos"): return rtuFrameSize(buffer, cls._rtu_byte_count_pos) raise NotImplementedException( f"Cannot determine RTU frame size for {cls.__name__}" ) class ModbusRequest(ModbusPDU): """Base class for a modbus request PDU.""" function_code = -1 def __init__(self, slave, transaction, protocol, skip_encode): """Proxy to the lower level initializer. :param slave: Modbus slave slave ID """ super().__init__(slave, transaction, protocol, skip_encode) self.fut = None def doException(self, exception): """Build an error response based on the function. :param exception: The exception to return :raises: An exception response """ exc = ExceptionResponse(self.function_code, exception) Log.error("Exception response {}", exc) return exc class ModbusResponse(ModbusPDU): """Base class for a modbus response PDU. .. attribute:: should_respond A flag that indicates if this response returns a result back to the client issuing the request .. attribute:: _rtu_frame_size Indicates the size of the modbus rtu response used for calculating how much to read. """ should_respond = True function_code = 0x00 def __init__(self, slave, transaction, protocol, skip_encode): """Proxy the lower level initializer. :param slave: Modbus slave slave ID """ super().__init__(slave, transaction, protocol, skip_encode) self.bits = [] self.registers = [] self.request = None def isError(self) -> bool: """Check if the error is a success or failure.""" return self.function_code > 0x80 # --------------------------------------------------------------------------- # # Exception PDUs # --------------------------------------------------------------------------- # class ModbusExceptions: # pylint: disable=too-few-public-methods """An enumeration of the valid modbus exceptions.""" IllegalFunction = 0x01 IllegalAddress = 0x02 IllegalValue = 0x03 SlaveFailure = 0x04 Acknowledge = 0x05 SlaveBusy = 0x06 NegativeAcknowledge = 0x07 MemoryParityError = 0x08 GatewayPathUnavailable = 0x0A GatewayNoResponse = 0x0B @classmethod def decode(cls, code): """Give an error code, translate it to a string error name. :param code: The code number to translate """ values = { v: k for k, v in iter(cls.__dict__.items()) if not k.startswith("__") and not callable(v) } return values.get(code, None) class ExceptionResponse(ModbusResponse): """Base class for a modbus exception PDU.""" ExceptionOffset = 0x80 _rtu_frame_size = 5 def __init__(self, function_code, exception_code=None, slave=1, transaction=0, protocol=0, skip_encode=False): """Initialize the modbus exception response. :param function_code: The function to build an exception response for :param exception_code: The specific modbus exception to return """ super().__init__(slave, transaction, protocol, skip_encode) self.original_code = function_code self.function_code = function_code | self.ExceptionOffset self.exception_code = exception_code def encode(self): """Encode a modbus exception response. :returns: The encoded exception packet """ return struct.pack(">B", self.exception_code) def decode(self, data): """Decode a modbus exception response. :param data: The packet data to decode """ self.exception_code = int(data[0]) def __str__(self): """Build a representation of an exception response. :returns: The string representation of an exception response """ message = ModbusExceptions.decode(self.exception_code) parameters = (self.function_code, self.original_code, message) return ( "Exception Response(%d, %d, %s)" # pylint: disable=consider-using-f-string % parameters ) class IllegalFunctionRequest(ModbusRequest): """Define 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 def __init__(self, function_code, xslave, xtransaction, xprotocol, xskip_encode): """Initialize a IllegalFunctionRequest. :param function_code: The function we are erroring on """ super().__init__(xslave, xtransaction, xprotocol, xskip_encode) self.function_code = function_code def decode(self, _data): """Decode so this failure will run correctly.""" def encode(self): """Decode so this failure will run correctly.""" async def execute(self, _context): """Build an illegal function request error response. :returns: The error response packet """ return ExceptionResponse(self.function_code, self.ErrorCode)