Creating a network adapter - how hard is it?

Question

I'm interested in building a little (commercial) device on top of Arduino. I want it to be able to interface with network. Network as in standard Ethernet, Cat5, RJ-45, etc.

I know that there is an Ethernet Shield, but it costs even more than the Arduino itself, and it's pretty big. Naturally, I want my device to be as small and as cheap as possible.

So I'm thinking about recreating an Ethernet module myself. The problem is - I haven't got any experience with Ethernet, nor do I have a good idea where to start looking. Thus I can't even say if my ideas are feasible.

Ultimately I would like the device to have three ports - one for incoming signal, two for outgoing, so the device is essentially a little switch where it is plugged in itself as well. The switching capabilities need not be very fast - the volume of data will be low. 10Mbit is more than enough, can be even slower.

If that is not possible, a single port for controlling the device itself will also do.

Another possibility I'm considering is power line communications - sending information through power lines. That's another area I've no experience with. What hardware should I be looking at, and where can I find information about the necessary software?

So - can anyone tell me if these ideas are feasible, and if yes - where should I start looking?

Answer 1

It's feasible, but you're going to need to delve deep into layer 2 of the network stack, especially if you want to build a tiny switch. If you steer clear of layer 3 you can avoid having to implement your own IP stack which would be a major pain.

I'd recommend starting with fully understanding how layer 2 works, from top to bottom. Once you've got a solid grasp of what's going on, especially with regards to the Ethernet spec, then you can worry about how you'd go about doing that on an Arduino. I don't have that much experience with the Arduino, but a buddy of mine implemented a layer 2 hardware stop-and-wait protocol on an FPGA a few weeks ago, so you should be able to get at least something rolling. you probably won't be able to go any faster than 10 Mbit unless you've got a pretty fast clock, though.

Answer 2

First of all I wouldn't think about the powserline technology is too complex, may be wi-fi can be possible, even though you have to deal with microwave frequency.

The best solution is as you said to find an Ethernet Shield, try to find an open hardware solution (drawing of the circuit). If you want to deal your own, you have to fnid a chip and threre are available, have a look on RS components. Probably most of the chips available are SMD, which means that is a pain to solder them, unless you are pretty clever and you have a microscope.

You can find a chip or a ready made solution here; http://www.beyondlogic.org/etherip/ip.htm

You could switch to Rabbit semiconductors, they have microcontroller ready with ethernet, but the dev kit is more expensive and the programming too.

This is a chip that you can use; http://www.wiznet.co.kr/en/pro02.php?&ss[2]=1&page=1&num=102