Modbus Library for Arduino

ModbusRTU, ModbusTCP and ModbusTCP Security

For detailes on the library usage visit documentation section.

Features

• Supports all Arduino platforms
• Operates in any combination of multiple instances of
  • Modbus RTU server
  • Modbus RTU client
  • Modbus TCP server for ESP8266/ESP32 and Ethernet library
  • Modbus TCP client for ESP8266/ESP32 and Ethernet library
  • MODBUS/TCP Security server (ESP8266)
  • MODBUS/TCP Security client (ESP8266/ESP32)
• Modbus functions supported:
  • 0x01 - Read Coils
  • 0x02 - Read Input Status (Read Discrete Inputs)
  • 0x03 - Read Holding Registers
  • 0x04 - Read Input Registers
  • 0x05 - Write Single Coil
  • 0x06 - Write Single Register
  • 0x0F - Write Multiple Coils
  • 0x10 - Write Multiple Registers
  • 0x14 - Read File Record
  • 0x15 - Write File Record
  • 0x16 - Mask Write Register
  • 0x17 - Read/Write multiple registers
• Callbacks driven design
• Real life complex examples:
  • ESP8266/ESP32 firmware update over Modbus
  • ModbusRTU to ModbusTCP bridge

Notes

1. The offsets for registers are 0-based. So be careful when setting your supervisory system or your testing software. For example, in ScadaBR offsets are 0-based, then, a register configured as 100 in the library is set to 100 in ScadaBR. On the other hand, in the CAS Modbus Scanner offsets are 1-based, so a register configured as 100 in library should be 101 in this software.
2. RS-485 transivers based on MAX-485 is working on at least up to 115200. XY-017/XY-485 working only up to 9600 for some reason.

For more information about Modbus see:

• Modbus (From Wikipedia, the free encyclopedia)
• MODBUS APPLICATION PROTOCOL SPECIFICATION V1.1b3
• MODBUS MESSAGING ON TCP/IP IMPLEMENTATION GUIDE V1.0b
• MODBUS over Serial Line Specification and Implementation Guide V1.02
• MODBUS/TCP Security Protocol Specification

Last Changes

// 4.1.1
+ Protocol: Fix wrong error code responce on non-existent register
+ ModbusTCP: Fix potential memory leak
+ API: cbEnable/cbDisable functionality extended
+ ESP-IDF: CMakeList.txt added
+ Examples: TCP-to-RTU fixed
// 4.1.0
+ API: Raw Modbus frame processing functionality
+ ModbusRTU: Precise inter-frame interval control
+ Examples: True ModbusRTU to ModbusTCP Server bridge
+ Examples: ModbusRTU respond to multiple ID from single device
+ ModbusRTU: Add direction control pin for Stream
+ STL: Add Reg count limitation to vector limit of 4000 (for ESP8266 and ESP32)
+ Settings: Added MODBUSIP_CONNECTION_TIMEOUT (ESP32 only)
+ Settings: Set MODBUSIP_MAX_CLIENTS = 8 for ESP32
+ ModbusTCP: Make using DNS names optional feature
+ ModbusRTU: Add separate RE/DE pins control optional feature
+ API: Drop support of Ethernet library v1
+ Examples: Teknic ClearCore ArduinoWrapper examples added
+ Examples: ModbusTCP to ModbusRTU example added
+ ModbusRTU: Flush extra delay optional feature
// 4.0.0
+ Support of all Arduino boards
+ ModbusTLS: ESP8266 Client/Server and ESP32 Client
+ ModbusTCP: ModbusEthernet - WizNet W5x00, ENC28J60 Ethernet library support
+ 0x14 - Read File Records function
+ 0x15 - Write File Records function
+ Examples: FW update over Modbus fullfunctional example
+ 0x16 - Write Mask Register function+ Test: 0x16
+ 0x17 - Read/Write Registers function
+ ModbusRTU: ESP32 SoftwareSerial support
+ Build with no STL dependency (switchable)
+ API: ModbusIP => ModbusTCP
+ API: Access control callback for individual Modbus function
+ API: Master/Slave => Client/Server according to [PRESS RELEASE](https://modbus.org/docs/Client-ServerPR-07-2020-final.docx.pdf)
+ Lot of code refacting and small fixes

Roadmap

// 4.2.0
- API: Alternative CRC calulation (reduced memory footprint)
- ModbusRTU: Static buffer allocation
- Test: Frame accuracy to specefication
- Buffer/packet size limitation support
- Slave/Server: slavePDU use early exit by return where possible
- Master/Client: Check frame size against header data where possible
- Master/Client: Additional responce data validation
- Free global registers and callbacks on remove last Modbus instance
- Test: push/pull functions
- ModbusTCP: Refactor connect by dns name (using native implementation for ESP32 etc)
// 4.3.0
- ModbusTLS: ESP32 Server
- Test: TLS ESP32 Server
- Test: TLS ESP32 Client
- Examples: TLS Certificate test Role extension and Alt-Name
- Examples: TLS Add example explanation
- ModbusTCP: ModbusAsyncTCP
- API: Extend API to allow custom Modbus commands
- Examples: Basic file operations
- Examples: Revising

Contributions

https://github.com/emelianov/modbus-esp8266

a.m.emelianov@gmail.com

Original version:

https://github.com/andresarmento/modbus-esp8266

https://github.com/andresarmento/modbus-arduino

prof (at) andresarmento (dot) com

License

The code in this repo is licensed under the BSD New License. See LICENSE.txt for more info.