hello, i m using c8051f020 microcontroller. i want to interface HMI touch screen with modbus protocol. i m planning to used ASCII format and 485 communication. i hav read the theory of modbus communication. can u guide me what all points should i consider about HMI and modbus?
Modbus has 3 different protocols:
Modbus ASCII Modbus RTU Modbus TCP/IP
You need to be sure that the device(s) you are talking to are working on Modbus ASCII if you are wanting to use Modbus ASCII. I would recommend searching around on the internet to download a Modbus protocol specification. Its a pretty easy specification to implement.
As far as "HMI", thats completely up to you and your situation. HMI is "Human-Machine Interface" and is basically a GUI (or just UI) that goes between your device and your machine. There is no "guide" to follow, if you are looking for guidelines on creating a GUI, check out books at Amazon.com on GUI. HMI's are VERY application dependant, I develop HMI's for a living.