Die Baugruppe Ethernut 1.3 wurde von egnite Software GmbH entwickelt und ersetzt das ursprüngliche ATmega103 Design, nachdem dieser Chip abgekündigt worden war. For Ethernet it uses Realtek's the RTL8019AS controller, which provides 10 Mbps. The ATmega128 provides 4 kByte internal RAM only, which is not sufficient for an Embedded Ethernet System. Thus, the board is equipped with 32 kByte external RAM.

One advantage of the Ethernut is, that all general purpose I/O ports as well as the external address and data bus are available at the expansion connector, which makes the board ideally suited for applications, which require some extra custom hardware to be attached. In addtion a RS232 port is available on a standard DB-9 connector.

Ethernut 2.0 has been designed by egnite as a compatible replacement for Ethernut 1.3 for two main purposes: First, it offers fast 100 Mbps Ethernet based on SMSC's LAN91C111 Ethernet controller. Second, 480 kByte banked RAM have been added to support new applications like streaming MP3 encoded audio data from Internet Shoutcast servers. The board also offers an additional RS485 interface.

Since August 2004 it has been replaced by Ethernut 2.1, which offers an additional 512 kBytes of serial flash memory.

The penality for all these enhancements is an increased power consumption and heat dissipation, mainly caused by the fast Ethernet interface.

Since egnite published its Ethernut design as Open Source Hardware, freely available even for commercial applications, many companies started using it for their own products. However, for low volume production, they prefer to use the original board. But there are cases, where the dimensions or connector placement does not allow this.

That's where www.hwgroup.cz, a Czech company, jumped in. They developed a tiny module, which is compatible with Ethernut 1.3 and can be easily integrated into a custom hardware design. Because egnite has registered the name Ethernut as a trademark, hwgroup named the module Charon II, after its forerunner Charon I, an 8051 based Ethernet module.

Some people argue, that even buying the bare Ethernut PCB, Ethernet controller and transformer etc. from egnite is many times the price of an ISA network card with all this already on board. Too true. So, how about using any cheap ATmega board and add an ISA connector to it.

Jochen Beck contributed all details to build such a real cheap solution.

The Medianut board can be attached to the Ethernut expansion connector and contains a VS1001K MP3 decoder, a Sony compatible infrared remote control receiver, a simple keyboard and a LCD interface.

The Charon Development Board board serves as a motherboard for the Charon I and Charon II Module. It comes with the required Ethernet transformer and RJ45 connector for the Charon Modules and additionally provides two RS232 ports, LCD interface, 8 bit dip switch input, 8 bit LED output, JTAG and ISP connector.