FreeMODBUS - A Modbus ASCII/RTU and TCP implementation

latest release v1.5 - 6 June 2010
Since version 0.9 FreeModbus supports an lwIP [1] port. The port is pretty generic and the FreeModbus port should be portable to another lwIP platform by simply recompiling it.

In addition this port includes a complete FreeRTOS port for the Motorola Coldfire targets and an ethernet driver for the MCF523x FEC controllers. The M5235x platform is a very powerful targets and features a Freescale MCF5235 processor with 2Mb Flash and 16Mb SDRAM. The development toolchain used is the GNU C compiler 3.4.6 with the Insight debuggers [2]. The files for this port can be found in demo/MCF5235TCP. The figure below shows a frame captured with the Ethereal network analyzer.

lwIP Modbus TCP frame

[1]: lwIP - A Lightweight TCP/IP stack is available from
[2]: Needs the Insight debugger from and the m68k-bdm patches for development available at

FreeMODBUS library and web page maintained by Christian Walter [wolti at sil dot at]
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FreeMODBUS is sponsored and provided by embedded solutions embedded solutions
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