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

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):
- 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).
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

Modbus Component

Installation

Features

Thread safety

Examples

API reference