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Charon 2: Ethernut embedded ethernet module
NOTE: Product end of life

Charon 2 is low-cost embbedded module based on the AVR ATmega MCU. It's full HW compatible with the free Ethernut project ( - Ethernut is an Open Source Hardware and Software Project for building Embedded Ethernet Devices).    You can design Charon 2 into you application, use RTOS and TCP/IP stack from the Ethernut project and start work on our examples. Original Ethernut Project as well as Charon 2 module are well documented..

Main Features

  • Full duplex IEEE 802.3 10 Mb/s Ethernet  
  • ATmega 128 RISC AVR microcontroller - up to 16 MIPS throughput
  • 128 kByte In-System Programmable FLASH ROM
  • 32 kByte SRAM + 4 kByte internal MCU SRAM
  • 4 kByte In-System programmable EEPROM
  • Module Programming (MCU internal FLASH 128 kByte)
    • In Systeme Programming over 6 wires with using PE0 & PE1 (USART 0), PB1 (SPI SCK) and MCU RSTpin.
    • JTAG programming (PF4, PF5, PF6, PF7)
    • Ethernet bootloader

  • Nut/OS - RTOS and TCP/IP stack
    (AVR GCC, ImageCraft ICCAVR, CodeVision AVR)
  • Module is full compatible with the Ethernut 1.3 board.

  • Development Kit and SW examples available.
  • Easy to use, easy to start, well documented..

Other related product pages:
- Charon 2 Development Kit
- Charon 2 demo application




  • Charon 2 module documentation
    Module dimension & pinout, pin description, Ethernet connection, application & module scheme.
    Memory map, fuses default values, programming details...
  • Charon 2 Development Kit documentation
    - Ch2 Developmet Board detailed description, connectors pinouts & description,
    - Getting started with the default demo application, testing all peripherals..
    - Detailed description of the example application & programming routines.
    - How to compile & programm to the Charon 2 module your application...
  • Charon 2 Application scheme
    How to connect Charon 2 module to the Ethernet and to your application. This scheme included in the Ch2 module datasheet.


Hardware Description

Power supply 5V DC / typ. 60mA max 80 mA
Dimension 47 x 39 x 12 mm (L x W x H)
Temperature Operating: -5 .. +50 °C
Ethernet 10BaseT – 802.3 (external signal transformer required)
2xSerial port TTL levels RxD,TxD (2x HW USART)
Programming SPI In-System Programming
JTAG interface (std. IEEE 1149.1)
MCU Xtal 14.745 MHz
SRAM / EEPROM 4+28 kB /(4kB MCU internal
RTL8019 EEPROM 256B (93C46)
27 I/O pins GPIO (7), ADC(4), JTAG (4), 2x RS-232 (4), SPI(4), I2C (2)
Power-on reset YES – 10% tolerance
WATCHDOG MCU internal WD only
Real Time Clock Separated timer 32.768 kHz


Module peripherals

Module interfaces Features:

  • 2x RS-232 serial port,
  • JTAG interface,
  • SPI interface,
  • 4x (+4x) AD Converter input,
  • 2x (+4x) PWM output,
  • TWI (I2C) interface,
  • 1x Analog Comparator,
  • separated on chip RTC oscillator

You can find detailed pin description in the Charon 2 - module datasheet, include combined functions etc..
Detailed electrical paramethers (pin driver description etc..) you can find in the Atmel's ATmega128 MCU datasheet.

Detailed module pinout description


Connecting to the Ethernet network

There is no placed Ethernet transformer, on the module. You have to place it to your application board. It’s a simple scheme and you can order this transformer from us with the module. We recommend connecting the Ethernet outputs according to the following recommended diagram.

You can choose separated transformer as “DIL14” size component (YCL 20F001N or Bothhand FS2022). If you need save PCB space, you can use transformer together with the RJ45 connector in one component (LF1S022).

YCL 20F001N – Transformer + RJ 45 connector

Separated transformer is a little better suited for industrial applications due to increased insulation strength, thanks to the standard packaging of the magnetic.

You can find some transformer datasheets on the CD to the Charon 2 Development Kit. You can see separated GND and GNDA on this scheme.

The termination resistor 100W on the TPI pair, known from the Charon I module is already placed on the Charon 2 module.

LF1S022 – Transformer integrated with the RJ45 connector

Code & Applications programming


About the Hardware, you are not lomited by the Charon 2 module only. You can run your SW on your own HW, or if you need to use external RAM space ammped peripherals, you can use original Ethernut boards :
  • Ethernut 1.x - Atmel ATmega128 CPU and a Realtek RTL8019AS Ethernet Controller - ..details
  • Ethernut 2.x - Atmel ATmega128 CPU and a LAN91C111 Ethernet Controller - ..details


The well documented software is an Open Source implementation of a Real Time Operating System called Nut/OS and a TCP/IP protocol suite named Nut/Net. Several application examples are provided, including an embedded Webserver, a simple RS232 to TCP/IP gateway and an Internet Radio playing MP3 streams.

There is originaly loaded demo application in the Charon 2 modules. It's a simple demo how to work with all peripherals on the Charon 2 Development Kit board, but it's well documented in the manual = it can help you a lot in beginning.

Application Development

Ethernut ProjectA well documented Ethernut API and more than 100 kByte program space and 20 kByte data memory are available to easily implement custom applications. The source code is written almost only in C and available for download. The licence allows its use in Open and Closed Source Projects without paying royalities, even not in commercial applications. The developer can choose between two different development environments, the freely available GNU AVR Compiler Collection for Linux and Windows and the commercially supported ImageCraft AVR Compiler for Windows.


Address space – Ethernut ver. 1.3F compared to Charon 2

Internal and external RAM address spaces are wired identically on the Ethernut 1.3F board and Charon 2 module. But the ethernet controller driver Realtek 8019AS is mapped in the I/O devices address space (0x8000 – 0xFFFE) many times (8000h, 8100h, 8200h, 8300h, …. FE00h, FF00h), according to original Ethernut 1.3F board where the RTL8019AS is mapped on the on 8300h-831F address only and space 8320h-FFFF is free to other I/O devices.


ATmega128 MCU SRAM space

  • 0x0000 – 0x10FF …internal Atmega128 CPU RAM space
  • 0x1100 – 0x7FFF …external 32 kB SRAM address space
  • 0x8000 – 0xFFFE…I/O devices address space

On the Charon 2 module it isn't possible to map devices to the address space (address and data bus isn't available on the connectors), finally it's 100% SW compatible with the original Ethernut board software.

Charon 2M

  • 128 kB SRAM
  • 512 kB SPI EEPROM

Check Charon 2M datasheet: Charon2M_en.pdf

Related & Development tools


Charon 2 Development Kit

The Charon 2 module is available in the Development Kit with the programmer, application board, SW examples and others:
  • Charon 2 module with MAC address included [600 071]
  • An HW STK-500 SPI programming adapter (RS-232)
  • LCD display 2x16 & DS1822 1-Wire thermometer
  • Charon I&II Development Board [600 072] with following peripherals :
    • Ethernet 10 Mbit interface
    • 2x RS-232 (2x DB9M - RxD, TxD, RTS, CTS, GND)
    • Programming : JTAG connector / SPI STK500 connector
    • LCD output interface (shift register)
    • 8x binary input, 8x binary output (shift registers)
  • SW examples and well documented Getting Started guide available
  • Easy to use, easy to start, well documented..


Development Kit contains full documented example on using all peripherals contained on Development Board (Digital Inputs/Outputs, 1-Wire thermometer, Serial port, LCD display, ..) using a simple WWW demo page.

Check the Charon 2 Development Kit manual

Hyperion Unit

Hyperion Unit is a baseboard & metal enclosure for the Charon 2 module. Tou can use it free for your SW application based on Charon 2 modules.

Datasheet: Hyperion_Unit.pdf (baseboard scheme, enclosure dimnsions)

The following peripherals are used on the base board:

  • 9..15V linear power supply
    or 6..35V switched power supply (for demand only)
  • Backup Battery 3.6 V (for demand only)
  • 1x full RS-232 serial port (75176 driver]
  • 1x RS-232 / 485 serial port
  • SPI serial FLASH (for demand only)
  • 10 Mbit Ethernet with using RJ45
  • 4x DIP switch
  • 4x screw terminal strip (RS-485 + power) (for demand only)

Contact us for more details..

FAQ & Support

Ask for the price or details:
 - Web:  http://
Country: *

Spam protection. How many is SIX times six?

Question:  What's your relation to the Ethernut project?
Answer:  HW group is official distributor of the Ethernut products in Czech Republic and we love this project. We designed our own Web51 systeme for the x51 MCU, but using Ethernut is saveing time for some of our applications. Because of it, we designed Charon 2 modules as higher version to the Charon I module based on 8051 family.

Question:  Are there any restrictions copyright to the Charon 2 modules?
Answer:  No, original Ethernut is free, Charon 2 and it's SW is free too.. Only our commercial end user products are useing Charon 2 technology and they are copyrighted.

Question: Where I can buy Charon 2 DK?
Answer:  You can buy it from us - check the pricelist. You can contact Egnite company (authors of the original Ethernut) in Germany or another our disributors...

Question: We want to control network device within our software. Do you have any SW examples, programming libraries or similar?
Answer:  Yes, there are some good examples demonstrating how to use our ethernet devices with Borland C++ and Delphi.
You can check some very easy communication examples using Visual Basic, JAVA and PHP. Check our Support & Download page.

Do you have more questions? - Try FAQs on the



Available now! You can order: Charon 2 module only or complete Charon 2 Development Kit.

We have a minimum of 20 pcs in stock at all times. It can be shipped via FedEx next day all over the world. We accept payement by Credit Cards or Wire Transfer, check our prices in the PriceList .

Or try to contact your nearest distributor of our products - International Distributors .  

OID Device type
600 074
End of life
Charon 2 DK set - (product photo)
Recommended starting set:
 - Charon 2 [600071]
 - Charon 2I DB board [600072]
  - HW STK500 programmer dongle
  - 1-Wire temperature sensor, LCD display 2x16 chars
 - DB9 LapLink cable 2m [600063]
 - Manual, CD
600 083
End of life
SP Duo prgrammer (product photo)
Recommended additional programmer to Charon 2 DK set
The original HW STK 500 is limited to AVR Studio 4.07 only, SP Duo isn't. With SP Duo you can program ATmega CPUs through RS-232 over SPI as like as JTAG interfaces.
600 071 Charon 2 (product photo) Stand-alone module only
600 258 Charon 2M (product photo)
128 kb SRAM, 512 kB SPI Flash on module - Module datasheet
600 055
End of life
Charon 2 E
Special module version woth RJ45 connector and Eth. transformer - for high volumes only!
600 072
End of life
Charon 2 DB board (product photo)
Development Board for Ch1 as like as Ch2, not module included
600 068
End of life
Ethernet set (product photo)
Components set for Charon module connecting to the Ethernet network. (Eth. transformer, RJ45 connector and 2 Capacitors for high Peak-2-Peak voltage)


Charon 2 DK set included

  • The Charon 2 module with MAC address and serial number on the label [600 071] . 
  • The Charon I&II Development Board (Shortly Development Board only) [600 072]. 
  • A LapLink serial communication cable with a DB-9 female socket on both ends [600 063]  
  • An HW STK-500 compatible programming adapter for serial RS-232 port [600 140]
  • Ch2 DK Accessories [600 141]
    • The DS1822 or DS18B20 1-Wire thermometer sensor 
    • A LCD display 2x16  
  • CD with all necessary software in the /Charon2/ directory



Recommended links & literature


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