modbus hardware interface for AVR micros

[makjee]

Hello all,

I have a digital IO (12 channels) board based on 8051 with RS485 interfacing. I have been able to successfully use the board but I want to improve it further.

I want to extend the channels to 16 or 24, so I am talking about 8 to 24 more pins (1 for output, 1 for input each). Hence I am looking at a 100pin package device.

Secondly, I want to implement the TCP version of Modbus. The selection of hardware is rather confusing. I can go for MMnet based cards, or include an ENC ethernet to SPI chip from Microchip, or select a 32 bit AVR C series supporting ethernet and develop from there. And if I just have to go learn a 32 bit processor is it better to get the ARM variants from Atmel and invest time in that? Implementing the actual protocol is not a big problem, I still want to spend much little effort on running the ethernet connection to work.

I intend to use AVR processors and had MEGA1280 i mind because of high pin count. But then again how does it fit inside the modbus TCP criteria? For that I require your input.

TIA

Mak

 

[sky_123]

Your actual question seems to be how to implement Ethernet and TCP/IP. Once you have Ethernet, you can implement modbus or
any other protocol on top of TCP/IP.

What is modbus TCP/IP criteria?

There is no 'criteria' to make TCP/IP suitable for modbus. TCP/IP is a standard that doesn't change for the higher-layer protocols.