SRC/STC-RS485-Modbus 2.0

SRC/STC-RS485-Modbus is a compact implementation of the Modbus RTU protocol for RS-485 networks, aimed at resource-constrained microcontrollers such as the STC 8051 family. It handles frame parsing/assembly, CRC-16 checks, timing, and addressing, and exposes a simple interface for mapping coils, discrete inputs, and holding/input registers to your application variables. Designed for half-duplex transceivers, it emphasizes low memory use and straightforward integration into existing embedded projects.

Key capabilities:

• Modbus RTU over RS-485 (half-duplex)
• Configurable device address, baud rate, parity, and timeouts
• CRC-16 integrity checking and inter-frame timing management
• Lightweight UART/timer abstraction with hooks for your hardware layer
• Register/coil map with read/write callbacks
• Optional interrupt-driven RX/TX and DE/RE driver-enable control
• Small footprint, portable embedded C

Typical applications:

• Adding Modbus RTU to sensor/actuator nodes
• Connecting STC-based devices to PLC/SCADA systems
• Retrofitting legacy equipment with an RS-485 interface

Prerequisites:

• An STC-series MCU and an RS-485 transceiver (e.g., MAX485 or equivalent)
• UART plus a timer for Modbus RTU timing gaps
• Basic familiarity with Modbus function codes and register mapping

Getting started:

• Wire the MCU UART to an RS-485 transceiver; add proper termination and biasing.
• Configure UART parameters and the device address.
• Define your Modbus register/coil map and implement read/write callbacks.
• Initialize the driver and call its processing routine from your main loop or ISRs.
• Validate with a standard Modbus RTU master.

Notes:

• Ensure DE/RE control matches your transceiver wiring.
• Follow RS-485 best practices: 120 Ω termination at the bus ends, fail-safe biasing, and a shared ground reference.

For exact APIs, examples, and any licensing terms, refer to the repository’s README and source comments.

SRC/STC-RS485-Modbus is developed by Thermokon Sensortechnik GmbH. The most popular version of this product among our users is 2.0. The name of the program executable file is SRC-STC-RS485-Modbus.exe.