I want to learn Modbus programming. I am trying to understand MODBUS Protocol. I did google and come with page https://en.wikipedia.org/wiki/Modbus Page show the different version of Modbus protocol. I work for embedded domain. Which version is useful and How to get start ?

 

Go to the official Modbus site https://modbus.org/
There used to be links for Tutorials etc.
Basically RTU or ASCII, I suspect that RTU is the version you should follow. although it is simple to jump from one to the other.
Keep in mind that RS485 is just one form of transmission only.
Max.

 

Indeed, modbus via rs485 is just one way of doing it. It is kind of an old method, albeit still reliable and by no means completely obsolete. RS485 hardware can be expensive as well so if your not dead set on RS485 for some reason modbus via rs232 would probably be the easiest and cheapest entry point. A lot of modbus these days has moved to modbus tcp which uses ethernet as the medium. At work we have shifted our process to modbus tcp for ease of maintenance and design. In small electronics projects ethernet may be a bit much, though cheap microcontrollers that already implement a tcp/ip stack are pretty common these days and could also be a fairly simple way to break into the field. Also modbus tcp can be implemented easily on any PC, so if it's just a learning exercise thats another way to get started with minimal cost and difficulty, assuming you have a PC available.