emModbus

SEGGER emModbus is a compact, production-grade Modbus protocol stack designed for resource-constrained embedded systems in industrial automation, building management, and process control applications. It implements the full Modbus specification across all transport variants, RTU and ASCII framing over UART, plus Modbus/TCP and Modbus/UDP over Ethernet, giving developers a single library that covers both serial and networked Modbus communication. With a master footprint of approximately 2.5 KB ROM and a slave footprint of around 3 KB ROM, emModbus fits comfortably on the smallest microcontrollers while maintaining full protocol compliance.

Master and Slave Editions

emModbus is available in separate Master and Slave configurations, each with a complete API and ready-to-run sample applications for all supported protocols. Both editions include companion Windows applications (provided as binary and source) for testing and development without dedicated hardware. The stack uses no dynamic memory allocation, ensuring deterministic behaviour and eliminating heap fragmentation concerns that are critical in long-running industrial systems.

Core Capabilities

• Full Modbus function code coverage: read/write coils, discrete inputs, holding registers, and input registers across all transport variants
• No dynamic memory allocation: deterministic behaviour and no heap fragmentation risk for long-running industrial installations
• Ready-to-run sample applications: provided for RTU, ASCII, TCP, and UDP on both Master and Slave editions
• Companion Windows test tools: binary and source code included, so Modbus communication can be validated without dedicated target hardware
• Hardware-independent transport layer: the UART and Ethernet abstraction is separated from the protocol logic, simplifying ports to new silicon

Integration and Portability

Written in ANSI C with a clean hardware abstraction layer, emModbus is fully portable across compilers and target platforms. For Ethernet operation it works with any TCP/IP stack that provides a BSD socket interface, and it is optimised for use with SEGGER emNet, which itself supports IPv4/IPv6, MQTT, and HTTP alongside the socket layer that Modbus/TCP relies on. A kernel abstraction layer provides native integration with embOS on embedded targets and Windows for desktop development, so a project already standardized on embOS for task scheduling gains Modbus support without introducing a second RTOS integration path. The royalty-free licensing model, one-time payment with no per-unit fees, keeps production costs predictable across volume ramps in industrial deployments, a factor that matters when Indian panel builders and machine OEMs are quoting fixed-price automation retrofits against tight BOM budgets.

SEGGER Ecosystem Integration

emModbus is one of several protocol and connectivity libraries in the SEGGER middleware family, alongside emNet for general TCP/IP networking, emMQTT for cloud telemetry, and emSSL for securing any of those channels with TLS. Teams building an industrial gateway that must speak Modbus to field devices while also publishing telemetry upstream over MQTT can combine emModbus and emMQTT on the same embOS-scheduled target without licensing conflicts, since all three libraries share the same royalty-free, source-code delivery model.