firmware-base/docs-c/modbus/ModbusRTU.md

title	description	keywords
ModbusRTU - Industrial Modbus-485 RTU Interface	A robust Modbus RTU interface for ESP32 industrial applications	modbus modbus-rtu rs485 industrial esp32 communication

ModbusRTU

Path: src/modbus/ModbusRTU.h

Revision History: Initial documentation

ModbusRTU is a comprehensive class that provides a robust interface for Modbus RTU communication over RS-485. It is designed for industrial applications on ESP32, offering efficient queue management, adaptive timeouts, and extensive error handling capabilities.

REQUIREMENTS

• Hardware:

  • ESP32 microcontroller
  • RS-485 transceiver (with DE/RE pin for direction control)
  • Serial interface for communication

• Software:

  • Arduino framework
  • ModbusClientRTU library
  • HardwareSerial for serial communication
  • ArduinoLog for logging

PROVIDES

• Enumerations:

  • E_InitState: Tracks initialization states (INIT_NOT_STARTED, INIT_SERIAL_STARTED, INIT_CLIENT_STARTED, INIT_READY, INIT_FAILED)

• Classes:

  • ModbusRTU: Main class for Modbus RTU communication
  • Manager: Device management class for handling multiple Modbus slave devices

FEATURES

• Non-blocking initialization and operation
• Flexible queue management with priority levels
• Read/write operations for coils and registers (single and multiple)
• Automatic value caching with synchronization status tracking
• Comprehensive error handling and retry mechanisms
• Adaptive minimum operation interval to adjust for network conditions
• Filter chain for operation validation and duplicate prevention
• Callback system for register changes, write completions, and error handling
• Status reporting and debugging utilities

DEPENDENCIES

• Arduino.h
• ModbusClientRTU.h
• HardwareSerial.h
• ArduinoLog.h
• ModbusTypes.h

graph TD
    ModbusRTU --> Arduino
    ModbusRTU --> ModbusClientRTU
    ModbusRTU --> HardwareSerial
    ModbusRTU --> ArduinoLog
    ModbusRTU --> ModbusTypes
    Manager --> ArduinoLog
    Manager --> ModbusTypes
    Manager --> ModbusRTU

BEHAVIOUR

stateDiagram-v2
    [*] --> INIT_NOT_STARTED
    INIT_NOT_STARTED --> INIT_SERIAL_STARTED: begin()
    INIT_SERIAL_STARTED --> INIT_CLIENT_STARTED: Serial init delay elapsed
    INIT_CLIENT_STARTED --> INIT_READY: Client init delay elapsed
    INIT_READY --> [*]: end()
    
    INIT_NOT_STARTED --> INIT_FAILED: Error
    INIT_SERIAL_STARTED --> INIT_FAILED: Error
    INIT_CLIENT_STARTED --> INIT_FAILED: Error
    
    state Operations {
        [*] --> Idle
        Idle --> QueueOperation: Read/Write request
        QueueOperation --> FilterOperation: Apply filters
        FilterOperation --> ExecuteOperation: If passed filters
        FilterOperation --> Idle: If rejected
        ExecuteOperation --> WaitForResponse: Operation sent
        WaitForResponse --> ProcessResponse: Response received
        WaitForResponse --> HandleError: Timeout/Error
        ProcessResponse --> Idle: Update cache
        HandleError --> Retry: If retries < max
        HandleError --> Idle: If max retries exceeded
        Retry --> ExecuteOperation: After backoff
    }
    
    INIT_READY --> Operations: Ready for operations

TODOS

PERFORMANCE

• Consider buffer pooling for multiple register operations to reduce memory fragmentation
• Implement batch processing for adjacent registers to reduce number of transactions
• Explore more granular timeouts for different device types or operation types

SECURITY

• Implement authentication mechanisms for secure Modbus communication
• Add validation for incoming data values to prevent exploitation
• Consider adding packet encryption for sensitive industrial applications

COMPLIANCE

• Ensure full compliance with Modbus RTU protocol specification
• Add support for additional function codes to cover all Modbus operations
• Implement proper exception code handling according to the standard

RECOMMENDATIONS

• Monitor operation success rates and adjust retry limits based on network reliability
• Configure adaptive timeouts based on device response characteristics
• Implement device-specific wrappers for common industrial equipment
• Use high priority flag for critical operations (safety or timing-sensitive commands)