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This library allows your ESP8266/ESP32 to communicate via Modbus protocol. The Modbus is a master-slave protocol used in industrial automation and can be used in other areas, such as home automation.
The Modbus generally uses serial RS-232 or RS-485 as physical layer (then called Modbus Serial) and TCP/IP via Ethernet or WiFi (Modbus IP).
For more information about Modbus see:
- Modbus (From Wikipedia, the free encyclopedia)
- MODBUS APPLICATION PROTOCOL SPECIFICATION V1.1b
- MODBUS MESSAGING ON TCP/IP IMPLEMENTATION GUIDE V1.0b
- MODBUS over Serial Line Specification and Implementation Guide V1.02
- Supported platforms are
- ESP8266
- ESP32
- STM32F103 and probably others (Modbus RTU only)
- Operates in any combination of multiple instances of
- ModbusRTU slave
- ModbusRTU master
- ModbusTCP server
- ModbusTCP client
- Reply exception messages for all supported functions
- 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
- Callbacks for
- Client connect (ModbusTCP)
- Server/Client disconnect (ModbusTCP)
- Read specific Register
- Write specific Register
- Slave transaction finish
- 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.
- For API refer API.md
- ModbusRTU maximum incoming frame size is determinated by HardwareSerial buffer size. For SoftwareSerial buffer must be set to 256 bytes.
- Probably it's possible to use ModbusRTU with other AVR boards using from ArduinoSTL.
- 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.
// 3.0.1
+ ModbusRTU: ESP32 possible send\receive failure fix
+ ModbusRTU: Non-ESP devices support
+ Restriction to registers count removed
+ Added bridge example
// 3.0.0
+ ModbusRTU Slave
+ ModbusRTU Master
+ Registers are now shared between Modbus* instances by default
+ Fix functions register count limits to follow Modbus specification (or RX buffer limitations)
+ ModbusRTU: Examples added
+ Test multiple Modbus* instances
+ Change to 'uint32_t eventSource()'. Implemented for ModbusRTU and ModbusIP both
+ Client: Allow to specify local TCP port (default is 502)
+ Server: Allow to specify TCP remote port for connection (default is 502)
+ Master\Client: Fix crash on Write Multiple Hregs
+ Master\Client: Fix crash on no callback function on read\write remote
+ Tests added
// ToDo later
- 0x14 - Read File Records function
- 0x15 - Write File Records function
- 0x16 - Write Mask Register function
- 0x17 - Read/Write Registers function
- ModbusIP: Support for non-ESP boards (using W5x00)
https://github.com/emelianov/modbus-esp8266
Original version:
https://github.com/andresarmento/modbus-esp8266
https://github.com/andresarmento/modbus-arduino
prof (at) andresarmento (dot) com
The code in this repo is licensed under the BSD New License. See LICENSE.txt for more info.