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emModbus—Modbus Software

  • Easy to integrate
  • Low memory footprint
  • ANSI-C code is completely portable and runs on any target
  • Follows the SEGGER coding standards: Efficient and compact, yet easy to read, understand, and debug
  • Supports ASCII, RTU and Modbus/TCP (and UDP) protocol
  • Sample applications for all protocols included
  • Kernel abstraction layer: can be used with or without any RTOS
  • Works out-of-the-box with embOS
  • Modbus/TCP can be used with standard socket interface and any TCP/IP stack
  • Works out-of-the-box with emNet
  • Project for executable on PC for Microsoft Visual Studio available

emModbus, SEGGER's implementation of the Modbus protocol, supports communication via UART (ASCII, RTU), Ethernet (Modbus/TCP and Modbus/UDP), and is capable to communicate with any Modbus compliant device. emModbus supports building master and slave devices which can even be combined in the same product. Also, multiple interfaces in the same product are supported. Each interface can be configured at runtime, making it possible to build a pretested library to be deployed in multiple projects for embedded solutions.

The communication protocol Modbus for embedded systems

Modbus is an open, mature, and straight forward communications protocol. It was originally published in 1979 by Modicon (Schneider Electric) and has since evolved into a standard communications protocol for industrial electronic devices. 

Modbus was specifically designed to be used in supervisory control and data acquisition systems, connecting a supervisory computer with several remote terminal units (RTU). It therefore uses a master-slave-technique in which one device, the master, initiates transactions (called queries).

Other devices, slaves respond by performing the action requested in the query and/or by supplying the requested data to the master.   

See Wikipedia for further information.

emModbus—Available Shipments

SEGGER offers emModbus in two distinct shipments, emModbus Master and emModbus Slave.


Master API (including samples for ASCII, RTU and Modbus/TCP)



Slave API (including samples for ASCII, RTU and Modbus/TCP)



ASCII frame encapsulation



RTU frame encapsulation



Modbus/TCP frame encapsulation (also supports Modbus/UDP)



Kernel abstraction layer for embOS and Windows



Modbus master application for Windows (binary)



Modbus master application for Windows (source)



Modbus slave application for Windows (binary)



Modbus slave application for Windows (source)




TCP/IP Stack

For usage of Modbus/TCP, emModbus requires a TCP/IP capable stack. emModbus can be used with any TCP/IP stack that supports BSD Standard Sockets.

Multi Tasking

Although emModbus can be used completely without a RTOS, it is recommended to use emModbus in a multi tasking system, at least when implementing a Modbus master.