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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).
In the current version the library allows the ESP8266/ESP32 operate as a master and/or slave, supporting Modbus IP via wireless network and Modbus RTU over serial. 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
- Operates as
- slave
- master
- Supports
- Modbus IP (TCP)
- Modbus RTU (RS-485)
- 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
- Master connect (ModbusIP)
- Master/Slave disconnect (ModbusIP)
- 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
- Modbus RTU 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.
// 3.0.0
+ 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
+ Allow to specify local TCP port for Slave (default is 502)
+ Allow to specify TCP port for remote Slave 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
// 2.1.0
+ Slave. Fix error response on write multiple Hregs\Coils
+ Slave. Fix writeCoil() for multiple coils
+ Master. dropTransactions()
+ Master. disconnect()
+ ~ModbusIP()
+ task() cleanup
+ Modify examples
+ Slave. Allow only single incoming master connection per IP
// 2.0.1
+ Master. Fix readCoil\Hreg\Ists\Ireg not read value from slave
+ Fix crash on disconnect with Arduino Core 2.5.x
// 2.0.0
+ Remove memory allocation checking for small blocks as anyway firmware will fail if so low memory available.
+ Change object's list implementation to *std::vector*
+ Modbus class refactoring
+ ModbusIP networking code refactoring and error reporting
+ Global registers storage to share between multiple Modbus* instances
+ Move rest of implementations from Modbus.h
+ Modbus master implementation
+ Move enum constants. E.g. MB_FC_READ_COIL => Modbus::FC_READ_COIL
+ Back to marking private for onSet, onGet, addReg and Reg methods
+ Added callback-related eventSource method, onDisconnect and transaction result callbacks
+ Extend register addressing to 0..65535
+ removeCoil, removeIsts, removeIreg, removeHreg, (removeReg)
+ readCoil, readHreg, readIsts, readIreg
+ push\pullCoil, push\pullHreg, pullIsts, pullIreg
+ pullCoilToIsts, pullHregToIreg, pushIstsToCoil, pushIregToHreg
+ optimize code around std::vector processing
+ extend removeCoil/Hreg/... to remove multiple registers
+ multiple callbacks => memory usage optimization
+ added removeOnSetCoil\... methods
+ added read/write/push/pullCoil/Hreg/Ireg/Ists() parameter to specify Modbus unit id
+ added ability to auto connect to slave. Setting is global. Disabled by default.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.