ModbusRTU and ModbusIP Master-Slave Library for ESP8266/ESP32 v3.0
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Release state: DEVELOPMENT Everything including API is subject to be changed during this stage.
Visit Releases page for stable one.
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
- Operates as
- 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 Standard C++ for Arduino (port of uClibc++).
- RS-485 transivers based on MAX-485 is working on at least up to 57600. XY-017/XY-485 working only up to 9600 for some reason.
// 3.0.0-DEVEL + 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 + CRC tables stored in PROGMEM + TX control pin support to work with MAX-485 - Test multiple Modbus* instances + Change to 'uint32_t eventSource()'. Implemented for ModbusRTU and ModbusIP both. + Documentation changes + Allow to specify local TCP port for Slave (default is 502) + Allow to specify TCP port for remote Slave connection (default is 502) // ToDo later - 0x14 - Read File Records function - 0x15 - Write File Records function - 0x16 - Write Mask Register function - 0x17 - Read/Write Registers function - 0x08 - Serial Diagnostics functions // 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.
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The code in this repo is licensed under the BSD New License. See LICENSE.txt for more info.