Pymodbus 4.0 upgrade procedure

Pymodbus 4.0 contains a number of incompatibilities with Pymodbus 3.x, however most of these are simple edits.

Convert to SimData/SimDevice

The old datastores:

• ModbusSequentialDataBlock,

• ModbusSparseDataBlock,

• ModbusSimulatorContext

are due to be removed in v4.0.0, starting with v3.13.0 the internal functionality are replaced by SimData/SimDevice.

However there is a simple path to upgrade:

ModbusSequentialDataBlock

This datastore makes sequential registers, corresponding to old style devices.

Example: .. code-block:

dev = ModbusDeviceContext(
            co=ModbusSequentialDataBlock(0x01, 15),
            di=ModbusSequentialDataBlock(0x01, [16]),
            hr=ModbusSequentialDataBlock(0x01, [17]),
            ir=ModbusSequentialDataBlock(0x01, [18])
)
server_context = ModbusServerContext(
                    devices={1: dev,
                             0: dev
                            })
await StartAsync**Server(context=server_context)

Device_id = 0 is at “catch-all”, that handles all devices not defined.

This is very easily converted to SimData/SimDevice

from pymodbus.simulator import SimData, SimDevice, DataType

devices = [SimDevice(1, simdata=(
                    SimData(0x01, values=15, datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS)
                )
            ),
            SimDevice(1, simdata=(
                    SimData(0x01, values=15, datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS)
                )
            )
]
await StartAsync**Server(context=devices)

ModbusSparseDataBlock

This datastore makes registers, with missing registers.

Example: .. code-block:

dev = ModbusDeviceContext(
            co=ModbusSparseDataBlock([1, 2, 3]),
            di=ModbusSequentialDataBlock({
                1: 6720,
                30: 130
            }),
            hr=ModbusSparseDataBlock([4, 5, 6]),
            ir=ModbusSparseDataBlock([7, 8, 9])
)
server_context = ModbusServerContext(
                    devices={1: dev,
                             0: dev
                            })
await StartAsync**Server(context=server_context)

Device_id = 0 is at “catch-all”, that handles all devices not defined.

This is very easily converted to SimData/SimDevice

from pymodbus.simulator import SimData, SimDevice, DataType

devices = [SimDevice(1, simdata=(
                    SimData(1, values=[1,2,3], datatype=DataType.REGISTERS),
                    [SimData(1, values=6720, datatype=DataType.REGISTERS),
                     SimData(30, values=130, datatype=DataType.REGISTERS)
                    ],
                    SimData(0x01, values=[4,5,6], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[7,8,9], datatype=DataType.REGISTERS)
                )
            ),
            SimDevice(1, simdata=(
                    SimData(0x01, values=15, datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS),
                    SimData(0x01, values=[17], datatype=DataType.REGISTERS)
                )
            )
]
await StartAsync**Server(context=devices)

ModbusSimulatorContext

This datastore is a complicated setup with actions and typechecking.

There are no very simple conversion, the configuration is grouped by datatypes then address.

Basically convert each address set to a SimData with datatype= the type of the group.

This will be amended, whenever there API changes are merged