Hi,

I want to communicate with my micro (Atmega32) and i want to use modbus protocol. I don't have any experience in using modbus!

i had to send some data to some micro controllers and they had to send response for me. now,i really don't know what is the usage of functions and their capabilities. is there any one to explain me?

 

Try: www.modbus.org Also, there are a number of modbus simulators in the Internet that you can use for free or for a reasonable price, e.g.

http://www.focus-sw.com/fieldtalk/modpoll.html
http://www.chipkin.com/useful-tools-and-applications-for-modbus/
http://www.modbustools.com/
http://www.plcsimulator.org/

William (Bill) L. Mostia, Jr. PE
Fellow

SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

 

Hi,

At www.modbus.pl you can find some modbus projects for Atmel uC.

Regards,
Andrzej

 

The official protocol specification is at www.modbus.org. Do NOT be alarmed at the number of functions, as you do not need to support most of them. Modbus is an old protocol, which is nothing but a 'memory transfer protocol', where a master/client and slave/server exchange bits in a table of 1-bit data, and words in a table of 16-bit data.

For most products, you form your data into an array of 16-bit integers, then support at least functions 3 and 6 to read the words in blocks and write a single register. Supporting function 16 (even if limited to 1 register at a time) will be helpful as some master tools use function 16, but not 6.