Beside the w5100 chip powered Ethernet shield, are there shields available with other chips?
The w5100 seems to make a lot up problems. There are many Ethernet related problems documented on several forums. Therefore I wondered if there are alternatives?
Yes, although none of them are quite as elegant as the official Ethernet Shield solution and may not work with all Arduino boards.
One option is the WIZ820io ethernet module at about $20. There's a great discussion on the adafruit forums regarding its use.
A more involved DIY choice is a shield based on the cheap (just $3) ENC28J60. A blog post at Open Electronics details the building and use of the shield while you can buy what appears to be a fully assembled version for ~$26.
There's a well-reviewed shield implementation of the ENC28J60 from DealExtreme that goes for about $18.
DealExtreme has another option (again based on the ENC28J60) that's smaller and not a shield. The board comes fully assembled for $10. It connects directly to the Arduino's SPI pins.
One of the advantages of the W5100 chip is that it handles the complex TCP/IP protocol stack on-chip. Since the most common Arduino, like the Uno, are based on an ATmega328 with only 2K of RAM, this is a significant help.
The ENC28J60 just a MAC and PHY chip. In other words, it is nothing more than a physical interface to the Ethernet part of the protocol stack. This means the TCP/IP part must be implemented within the 2K of RAM of the Arduino. This does not leave much RAM for your project to do much useful.
While the ENC28J60 tends to be much cheaper than than W5100, it tends to significantly limit the type of code you can run. For example Twitter-based projects, which tends to use a lot of strings, it is difficult to implement without exhausting the Arduino's RAM.
