I want to design a software in "C programming language" for Atmel microcontrollers. Can somebody help me for this.

 

I would expect Atmel can. I have also seen a
series on porting Linux to various Atmels. If you Google for it, I would expect you could find information on a GCC tool chain for Atmel.

Regards
cww

 

The following is from the Atmel web site.

http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4118

AVR32 GNU Toolchain is a set of standalone command line programs used to create applications for AVR32 microcontrollers. The applications run either as embedded applications or on top of an embedded operating system, e.g. Linux®.

The tools may be used in a chain, so that the output of each tool becomes the input for the next. Several of the tools are based on tools from GNU (www.gnu.org), and some are developed by Atmel.

* Runs on Microsoft® Windows® and Linux platforms
* Cross compiler for AVR32 devices
* Assembler and linker for AVR32 devices
* Debugger for AVR32 devices
* Flash programming tools for AVR32 devices
* C-libraries for development of C/C++ programs

**********************************************

The above is for the 32 bit Atmel hardware. They have packages you can download from that page for various Linux versions, but you can get the same tools straight from a lot of distro repositories, which should be more up to date and a lot easier to install.

A lot of Linux distros have more tools for the 8 bit Atmel hardware as well, including simulators, emulators, programmers, etc.

 

You don't need to use 32bit Atmel products. An Atmega8 should be sufficient. This has an uart interface wich can be used for rs232 after a level conversion ttl 5Volt to +-10V rs232 standard. This can easily be done with a simple circuit using a max232 chip. Atmel has a free C programming enviroment downloadable from atmel.com

Pretty easy job, you should know the Modbus protocol very well, look for a detailed description of the Modbus protocol, Modbus reference guide.

Basically, on the microcontroller you just read and write to the serial port, the Modbus reference guide tells you what to write or read from the port.