FreeMODBUS - A Modbus ASCII/RTU and TCP implementation


latest release v1.5 - 6 June 2010
 
The initial port was done with the Mega168 Mini Module from Embedit Mikrocontrollertechnik. It features a 8Bit AVR ATMega168 controller with 16KByte Flash, 1KByte SRAM and 512Byte EEPROM. The development toolchain used is WinAVR. Since version 1.0 Freemodbus also supports the ATMega8, ATMega32, ATMega168 and ATMega169 microcontrollers. In addition it includes support for the RS485 driver DS75176. The files for this port can be found in /demo/AVR

Depending upon the selected functions and transmission modes (ASCII/RTU) the following resources are used:

Module Code RAM (static)
Modbus RTU (Required [1])1456Byte266Byte
Modbus ASCII (Optional)1222Byte16Byte
Modbus Functions [2]1602Byte34Byte
Modbus Core (Required)608Byte75Byte
Porting Layer (Required)704Byte7Byte

Mega168 Mini Module

[1]: Includes a special implementation of the CRC16 calculation algorithm to use values from the flash memory.
[2]: All supported Modbus functions compiled in.


FreeMODBUS library and web page maintained by Christian Walter [wolti at sil dot at]
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