Internet of Things - Serial to Ethernet Adapter

I have been working on a number of projects recently which would all require an internet connection either for fetching data or uploading data, in other words the Internet of Things!

One of the easiest way to get connected is via an ENC28J60 ethernet module, these devices deal with the low level stuff and connect to your system via an SPI connection, they are also very cheap. The problem with these boards is that they still require a lot of code to make them work, I am currently developing with an arduino and the ATmega328P microcontroller and the ethernet code takes up about 25k of the 30k thats available, this leaves very little space left for the rest of the program.

One solution would be to use something more powerful like the Arduino Mega 2560 but these are very expensive. As an alternative I have opted to use two microcontrollers in the projects I am working on. One dedicated to internet communications and the other for the rest of the program, this takes up a little more space but is significantly cheaper, it's also very modular allowing me to reuse code and hardware.

With this in mind I have been working on a Serial to Ethernet adapter, I have had a prototype running for a couple of weeks and I have just had back my first dedicated PCB for this project. This boards works as expected so I am about to send of the next revision of the board, I have removed some unneeded components and outputs and reduced the size a lot.

I still have a few improvements to make to the software but hopefully at the end I will have a very useful little board that I can use to add an internet connection to projects and thats also very cheap, I am currently hoping for a total cost of less than £3.

The ATmega328P chip costs less than £1 while the ATmega2560 is around £10 so for situations where tasks can be easily separated into distinct parts with basic comms between them I think this is a good solution.