Ethernet ENC28J60

Microchip ENC28J60 is an Ethernet controller with SPI interface that is used in some Arduino Ethernet Shields (these are called "etherShield"s). Unfortunatelly, the standard Arduino Ethernet Shield (called "Ethernet Shield") have the WIZnet W5100 controller - and only the version with W5100 is oficially supported by the Arduino standard library.

There is a library called etherShield but it is very hard to use (you need to manage ARP and TCP packets in the "application layer"). So, I decided to write a new socket.c (based on etherShield's code) that exposes the same API the standard Ethernet Shield library exposes.

The goal of the project will be achieved as an Arduino user can use the same code for both Ethernet controllers (W5100 and ENC28J60). With this project I can also identify architectural problems in the standard Ethernet library implementation and make it better.

Arduino with etherShield (based on Microchip ENC28J60 Ethernet controller)

Usage

Download the tarball at GitHub and put the library inside sketchbook/libraries/ folder. If you just want to test without debugging, use the examples WebServerSimple and WebServerSimpleLED.

WARNING: This is a work-in-progress project and need more tests to be used in production environments!

Using with Arduino Mega

This library is compatible with Arduino Mega, but you need a hardware-hack so ENC28J60 can communicate (using SPI) with Arduino. Please refer to http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/ for more information.

Limitations

For now that are some limitations that will be removed in a near future:

Just one socket per time;
Only support for TCP server -- connect(), sendto() and recvfrom() don't work yet;
Can only "answer" to the last packet received.

Architecture

WIZnet W5100 Library

In the standard Ethernet library, the Ethernet, Server and Client classes use the socket API to send and received data over the network. The socket library uses the "driver", (w5100 library) to communicate with the controller. Something like this:

{Ethernet.cpp, Server.cpp, Client.cpp} ↔ socket.c ↔ w5100.c

Microchip ENC28J60 Library

In my implementation I have another layer: ip_arp_udp_tcp. This is a kind-of socket layer (it is really not a socket layer since it doesn't provide a kind of socket API -- merely we have here a lot of helper functions to read, identify, create and send packets using the "driver" enc28j60). For now, we have this:

{Ethernet.cpp, Server.cpp, Client.cpp} ↔ socket.c ↔ ip_arp_udp_tcp.c ↔ enc28j60.c

In a near future I want to replace all ip_arp_udp_tcp layer in the socket layer, so the architecture will be more like the standard Ethernet library:

{Ethernet.cpp, Server.cpp, Client.cpp} ↔ socket.c ↔ enc28j60.c

When this goal is reached we can create a single socket.c that communicate with one or another controller (W5100 or ENC28J60).

Next Goals

Finish implementation of connect()
Modify send() to acomplish TCP client sockets
Implement sendto() and recvfrom()
Support for multiple sockets
Put all the features of ip_arp_udp_tcp.c in socket.c (and then removes ip_arp_udp_tcp.*)

How To Debug

If do you want to test and modify this library, probably you will want also to enable debugging. You can see what is happening using the Serial Monitor on Arduino IDE if you uncomment the line below in the file utility/socket.h:

//#define ETHERSHIELD_DEBUG

Please use the examples WebServerDEBUG and WebClientDEBUG for debugging (and to learn how to do it).

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