Modbus Component

Installation

The component requires ESP-IDF 5.3 and higher and is installed using IDF Component Manager.

Add this to the idf_component.yml in the project main directory or in the component directory:

dependencies:
  plasmapper/pl_modbus: "^1.2.1"

Add this to the source code:

#include "pl_modbus.h"

Add extern "C" to the app_main function:

extern "C" void app_main(void) {...}

Add this to the sdkconfig.defaults in the project directory or configure the values using Project Configuration:

CONFIG_COMPILER_CXX_RTTI=y
CONFIG_LWIP_SO_RCVBUF=y

Features

1. PL::ModbusClient - a Modbus client class.

   • RTU, ASCII and TCP protocols via a single stream (UART, USB etc) or a network connection.

   • Implemented read/write functions (Modbus function codes):

     • PL::ModbusClient::ReadCoils() / PL::ModbusClient::ReadDiscreteInputs() / PL::ModbusClient::ReadHoldingRegisters() / PL::ModbusClient::ReadInputRegisters() (1/2/3/4)

     • PL::ModbusClient::WriteSingleCoil() / PL::ModbusClient::WriteSingleHoldingRegister() (5/6)

     • PL::ModbusClient::WriteMultipleCoils() / PL::ModbusClient::WriteMultipleHoldingRegisters() (15/16)

   • Splitting single read/write requests into multiple requests with valid number of memory elements.

   • Automatic reconnection to the device.

   • Support of multiple devices on the same stream or TCP client.

   • To implement other Modbus function codes:

     • Inherit PL::ModbusClient and override PL::ModbusClient::ReadRtuData() method to read custom function response data.

     • Use public or protected PL::ModbusClient::Command() method (see the implemented read/write methods).

2. PL::ModbusServer - a Modbus server class.

   • RTU, ASCII and TCP protocols via a single stream (UART, USB etc) or a network connection.

   • Several PL::ModbusServer::AddMemoryArea() methods, PL::ModbusMemoryArea and PL::ModbusTypedMemoryArea classes to create simple and complex combinations of Modbus server memory areas.

   • Same implemented read/write functions as for the client.

   • To implement other Modbus function codes:

     • Inherit PL::ModbusServer class and override PL::ModbusServer::ReadRtuData() method to read custom function request data.

     • Override PL::ModbusServer::HandleRequest() method to handle the client request with a custom function code.

Thread safety

Class method thread safety is implemented by having the PL::Lockable as a base class and creating the class object lock guard at the beginning of the methods.

The stream PL::ModbusClient locks both the PL::ModbusClient and the PL::Stream objects for the duration of the transaction. The network PL::ModbusClient locks both the PL::ModbusClient and the PL::TcpClient objects for the duration of the transaction.

The stream PL::ModbusServer task method locks both the underlying PL::StreamServer and the PL::Stream objects for the duration of the transaction. The network PL::ModbusServer task method locks both the underlying PL::TcpServer and the client PL::NetworkStream objects for the duration of the transaction. The default PL::ModbusServer::HandleRequest() locks the accessed PL::ModbusMemoryArea for the duration of the transaction.

Examples

UART client

Network client

UART server

USB server

Network server

Server memory areas

Server user-defined function

API reference

• Types
  • ModbusInterface
    • stream
    • network
  • ModbusProtocol
    • rtu
    • ascii
    • tcp
  • ModbusMemoryType
    • coils
    • discreteInputs
    • holdingRegisters
    • inputRegisters
  • ModbusFunctionCode
    • unknown
    • readCoils
    • readDiscreteInputs
    • readHoldingRegisters
    • readInputRegisters
    • writeSingleCoil
    • writeSingleHoldingRegister
    • writeMultipleCoils
    • writeMultipleHoldingRegisters
  • ModbusException
    • noException
    • illegalFunction
    • illegalDataAddress
    • illegalDataValue
    • serverDeviceFailure
    • acknowledge
    • serverDeviceBusy
    • negativeAcknowledge
    • memoryParityError
    • gatewayPathUnavailable
    • gatewayTargetDeviceFailedToRespond
• PL::ModbusClient class
  • PL::ModbusClient
    • ModbusClient()
    • ModbusClient()
    • ModbusClient()
    • ModbusClient()
    • Lock()
    • Unlock()
    • Command()
    • ReadCoils()
    • ReadDiscreteInputs()
    • ReadHoldingRegisters()
    • ReadInputRegisters()
    • WriteSingleCoil()
    • WriteSingleHoldingRegister()
    • WriteMultipleCoils()
    • WriteMultipleHoldingRegisters()
    • GetStationAddress()
    • SetStationAddress()
    • GetProtocol()
    • SetProtocol()
    • GetReadTimeout()
    • SetReadTimeout()
    • GetDelayAfterRead()
    • SetDelayAfterRead()
    • defaultReadTimeout
    • defaultBufferSize
    • defaultNetworkProtocol
    • defaultNetworkStationAddress
    • maxNumberOfModbusBitsToRead
    • maxNumberOfModbusBitsToWrite
    • maxNumberOfModbusRegistersToRead
    • maxNumberOfModbusRegistersToWrite
    • ReadRtuData()
    • ReadFrame()
    • WriteFrame()
    • GetDataBuffer()
• PL::ModbusServer class
  • PL::ModbusServer
    • ModbusServer()
    • ModbusServer()
    • ModbusServer()
    • ModbusServer()
    • Lock()
    • Unlock()
    • Enable()
    • Disable()
    • AddMemoryArea()
    • AddMemoryArea()
    • IsEnabled()
    • GetStationAddress()
    • SetStationAddress()
    • SetTaskParameters()
    • GetBaseServer()
    • GetProtocol()
    • SetProtocol()
    • GetReadTimeout()
    • SetReadTimeout()
    • GetDelayAfterRead()
    • SetDelayAfterRead()
    • GetName()
    • SetName()
    • enabledEvent
    • disabledEvent
    • defaultName
    • defaultReadTimeout
    • defaultBufferSize
    • defaultNetworkProtocol
    • defaultNetworkStationAddress
    • maxNumberOfModbusBitsToRead
    • maxNumberOfModbusBitsToWrite
    • maxNumberOfModbusRegistersToRead
    • maxNumberOfModbusRegistersToWrite
    • ReadRtuData()
    • HandleRequest()
    • WriteExceptionFrame()
    • ReadFrame()
    • WriteFrame()
    • GetDataBuffer()
• PL::ModbusMemoryArea class
  • PL::ModbusMemoryArea
    • ModbusMemoryArea()
    • ModbusMemoryArea()
    • ModbusMemoryArea()
    • OnRead()
    • OnWrite()
    • Lock()
    • Unlock()
    • Clear()
    • type
    • address
    • numberOfItems
    • data
    • size
• PL::ModbusTypedMemoryArea class
  • PL::ModbusTypedMemoryArea
    • ModbusTypedMemoryArea()
    • ModbusTypedMemoryArea()
    • ModbusTypedMemoryArea()
    • OnRead()
    • OnWrite()
    • Lock()
    • Unlock()
    • Clear()
    • data
    • type
    • address
    • numberOfItems
    • size