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

The fabulous Charon of the Roman mythology was the boatman on the river Styx, which separated the world of the living and the world of the dead. His boat was the only "interface" crossing that boundary.
Our Charon I module is named after him because it is also an interface. Usually, it converts Ethernet to RS232 or RS485 and vice versa. However, it can also be used as a WWW server, control inputs and outputs, and so on, utilizing either our finished firmwares or your custom one. It's a low-cost embedded Ethernet module designed to enable you to easily add Ethernet connectivity to your existing products.

Main Features

  • Ready-to-go Serial-to-Ethernet module to network enable any serial (RS-232/RS422/485 TTL) device.
  • 10 Mb/s Ethernet, 115.2 kBd serial interface
  • Support TCP Server, Client, Client/Server, UDP
  • Virtual Serial Port for Windows 2000 and higher free (RFC2217 compatible = remote baudrate variable, I/O pins status..).
  • 8 I/O pins accessible over the TCP/IP (NVT protocol).
  • Single +5V input, 0.3 W low power consuption
  • Everything under opened RFC standard and well documented.
  • A lot of support PC programming examples ( MS Visual Basic, Delphi, Borland C++, JAVA, PHP and others) and technical backgroud..
  • Good technical support and fast FW updates.
  • Module is programmable using x51 ASM (Web51) or ANSI C (Keil od SDCC - Web51-C)
  • Charon I is pin compatible with the Charon 2 module (fully custommer programable module with RTOS in the ANSI C, it's open source project).



Download & Datasheets


Technical specifications

Basic features of the module

  • Easily embedded module, dimensions: 3x4 cm = 1.2 x 1.6" (W x L)
  • TTL RS-232 serial port with HW handshake
  • RJ 45 interface - 10BASE-T 
    (requires external ethernet transformer on the application board)
  • 8 I/O pins controllable though Ethernet or expandable with using external SHIFT registers..
  • Easy to update firmware or to program the module, FW update over the serial port only.

Power supply 5V DC / typ. 50 mA - max 65 mA
Dimension 44 x 35 x 12 mm (L x W x H )
Temperature Operating: -10 .. +70 °C 
Ethernet 10BaseT – 802.3 (external signal transformer required)
Serial port RS-232 TTL levels RxD,TxD, RTS, CTS (HW USART)
Programming ISP over RS-232 (Atmel Flip SW)
MCU Xtal 18.432 MHz (X2 mode)
SRAM / EEPROM 32 kB / 2 kB (MCU internal)
RTL8019 EEPROM 256B (93C46)
I/O pins 14 = 4 (RS232) + 8 (P1) + 2 
Power-on reset YES – 10% tolerance
WATCHDOG MCU internal WD only


Pin description

TPO+, TPO- 10Base -T Differential Outputs OUT -
TPI+, TPI- 10Base -T Differential Inputs IN -
LINK Link and Activity Indicator OUT -
GND GND for Ethernet shield GND -
RxD P3-0 pin - Receive Data IN Module programming
TxD P3-1 pin - Transmit Data OUT Module programming
CTS P3-3 pin (INT1) - Clear to Send IN -
RTS P3-5 pin (T1) - Request to Send OUT -
PSEN Connect to GND and RESET for programming. IN Module programming
+5V Power +5V DC 15-80 mA PWR -
P1 (P1.0 .. P1.7) Direct 8. bit port P1. I/O -
INT0 P3-2 pin (INT0) - universal pin I/O -
T0 P3-4 pin (T1) - universal pin I/O SETUP mode
( RS232-9600 8N1)
RST RESET module I/O -
GND Main ground GND -

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 simple and you can order this transformer from us with the module. We recommend connecting the Ethernet outputs according to the following 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

Charon Applications

  • Using the Charon I module you can make a Virtual Serial Com port, which might be placed where ever you want and connected to your PC as for example COM 7.
  • Using Virtual Com you can connect a Bar Code reader, Serial printer, LCD display or any other peripherals communicating via RS-232 serial port. These peripherals are connected to PC by RS-232 line which is extended using Ethernet, so the periphery might be far away from the PC.
  • You can use the UDP or TCP Client, TCP Server or TCP Client/Server mode.
  • You should combine remote serial port RS-232 control with 8x I/O ports through Ethernet. So you can connect for example a heating system in your house and switch on/off the heater, air condition, security system and so on.
  • Remote supervising of industrial devices using for example Open View software, or you can create your own application and use lots of examples (Borland C++, Delphi, MS Visual Basic, Java, PHP).
  • Charon I might be also used for replacing the standard serial phone modem.
  • There is special support for extending the RS-485 line, include 9. bit comunication support..


Charon I - various firmware 

There are some finished firmwares free for use with the Charon I module. You can find detailed description on linked detailed pages, it's just a simple FW description. You can download the HEX files to the module on this Charon I main page - Download chapter.

The module FirmWare can be uploaded with using our older RD2 Flasher, but we recommend to use the Atmel FLIP. Be careful for used MCU, there can be mounted RD2 or RE2 version. Choose right type in the Flip.

IMPORTANT: You have to set configuration to default state after any FW upload. (The "D0" command in the RS232 Setup mode with using the Converter FW for example).

1) Converter FW

Default loaded FW for easy-to-use serial port and 8x I/O pins to the TCP/IP and UDP/IP protocols, support for NVT control according to RFC2217. 

Application configuration:

  • RS-232 Setup (standard serial terminal)
  • UDP Config on a local segment with using the Hercules SETUP utility.
  • TCP/IP Setup - Remote terminal configuration via TCP/IP. 

Asynchronous interface – Support for serial line protocol autodetection. Full/half duplex mode, direction switching for RS485. Any speed from 50 to 115200 Bd, all settings of parity, stop bits, etc. Support for 9-bit data transfers. 


  • The settings (IP, Mask, Gateway…) might be done using serial link, TCP/IP or UDP protocol.
  • There is also a Virtual serial port driver available.
  • NVT (Network virtual terminal) support, which is usable for setting the baud rates, I/O pins and so on
  • TEA (Tiny Encryption Algorithm) for the connection authenticity control (if you are setting some parameters via TCP/IP or UDP)
  • The module with this firmware can work as a client, server or server/client
  • It has UDP communication implemented (packet filtering, which must be used for example in fig.2-b )
  • Serial RS232 port accessible over an Ethernet network.
  • Configurable communication speed 300..115200 Bd, handshake (CTS/RTS, Xon/Xoff, none)
  • RJ 45 interface   - 10BASE-T  and RS-232.
  • Parameters configured locally over RS232 or over the Ethernet using a Windows application
  • Support for TCP/IP data transfer - TELNET-like client + optional NVT support (Network Virtual Terminal)
  • Option to activate UDP transfer with RS485 support.
  • Triggers for packet start and packet end.
  • Support for passive or active mode (the converter can establish a connection with the remote side upon serial line activity)
  • Two devices can extend a serial port over the Ethernet.
  • Security measures consist of a fixed specification of the remote IP address range and optional connection authorization using the 128-bit TEA encryption algorithm.
  • Support for interfacing with special software, or a Windows configuration application


Parallel outputs – The module contains 8 binary I/O pins that can be controlled directly via NVT according to RFC2217 extensions. It is possible to configure data transfer between two modules; these pins are then simply "connected" through the Ethernet. The application is fully compatible with the "boxed" version of the converter and is compatible with all existing communication libraries, ready-made subroutines, configuration software, solution examples, application notes, etc.

This FW doesn’t support HTTP Web control = you can't access data though the WEB prowser.

2) Metex multimeter connection FW

This firmware can connect the Metex multimeter, which is not near enough to connect it via serial RS-232 line. This firmware can access this kind of device, connected through Charon I to Ethernet.

It's just demo how you can use the Charon module to application where TCP server creating the WWW pages based on data measured from the technology, connected by the converter module.

This is a special FW, because METEX multimeter requires RS-232 reply every 3 minutes - without this, multimeter will use save mode and power off.

More Metex multimeter FW details..


3) Home Web Control FW

The Charon I module with this firmware controls the RS-232 line, 8x inputs and 8x outputs, LCD display and up to 4 one-wire thermometers via Ethernet network, using Telnet or Web browser application. We should recommend you to use the Charon I Development Kit for testing and using the firmware. You can use the Charon I&II DB, which contains shifted peripherals and it's normally distributed with the Charon 2 module.

The module is a small WWW server, so it has its own IP address and it provides standard WWW service on port 80. Than you can see the I/O ports status, the temperatures and so on. You can also set the password (in the RS-232 line setup) for making the changes on the outputs ports.

  • You can define a set of events. If the events are done, an e-mail will be sent to defined address
  • The Web interface, which provides you reading of 4 temperature sensors, 8xI/O pins control and the state displaying.
  • The LCD display 2x16 control
  • All the output pins are protected by password

Full source code (ASM) of this application is contained in the Web51 Development Kit.

More Home Web Control FW details..

4) SNMP Thermometer FW

Demo of SNMP control options. Custom definition of MIB is not available, it is only a demo of remote controlling application and configuration over SNMP. 1 thermometer, 8 Inputs, 8 Outputs, LCD display etc connection demo.

There is a chance to program a lot of SNMP applications in C language and our development kit „Web51 ANSI C – SNMP“ contains many examples, which helps you to get in quickly. The most advanced application is „SNMP I/O Thermometer“, which you can use together with JAVA application „Thermometer“, instead of a common SNMP client, it controls a serial RS-232 link, up to 32 binary inputs/outputs and 4 1-Wire thermometers..

  • This is used for remote application control.
  • Supports also UDP protocol and SNMP with MIB available.
  • The whole firmware is written in the ANSI C language
  • You can use some of the professional remote control manager (Open view or demonstration software written in JAVA)
  • The RS-232 access via SNMP (you can control devices as for instance microwave communicator, HUB, Switch or any other having a serial line)
  • 8x Input and 8x Output pins control
  • A chance to connect one temperature 1-Wire sensor


Full source code (ANSI C) of this application is contained in the Web51-C Development Kit. Only some SNMP parts are distributed in the compiled version.

More SNMP Thermometer FW details..


These are the the main firmwares, which are available now. Each firmware contains also a PC application, which demonstrates the functionality and might be a good example for you, if you would like to write your own PC application.

Useful Utilities

Hercules SETUP Utility

For the SETUP and testing of the device we have developed a free utility "Hercules SETUP". It's a simple :
 - Serial port terminal,
 - TCP telnet terminal,
 - UDP terminal,
 - HW devices UDP Config
 - TCP/IP NVT commands and TEA authorization supporting terminal

It's our recommended utility for SETUP and testing of all devices. You can download the latest version from the Internet, or you'll find it on our CD.

HW Virtual Serial Port

The Virtual serial port driver for Windows is a software tool, which adds a virtual Comm port to the system as for example COM5 and all the data from this port are re-directed to the other HW device. The Virtual serial port is mostly used if connecting some RS-232 serial link by USB or Ethernet. The HW Virtual Serial Driver is primary designed for our devices, but you can use it for other devices for free.

The PC with the Virtual driver should work also as a server, so the connection might be initialized from the external device by sending any data to the remote port. The convertor opens the connection with PC and sends the data to the virtual com. The whole situation is quite the same as in case with a normal serial port, but our device can be as far away as you want.

The virtual driver can work as a client or server !


Sample Codes, Code library & Examples

The TEA encryption & Authorisation algorithm

TEA (The Tiny Encryption Algorithm) is a simple password authorization system for the secure device access. For more information, read our support manual, how to use & implement TEA

NVT (Network Virtual Terminal) description

Command communication with the TCP/IP device over the Ethernet network using the NVT (Network Virtual Terminal). It can be used according to the RFC2217 specification to change baudrate on remote Virtual Serial Port or to SET or READ remote I/O pins for example.



Related & Development tools

You can write your own application for the Charon I module in ASM (x51 Assembler) or in ANSI C (uC KEIL or SDCC) with using one of these projects.


  • Project Web51 -  
    Write your own TCP/IP od UDP/IP application to the Charon I module (8051 MCU) in ASM.
  • Project Web51-C
    Development kit for creating embedded Ethernet UDP and SNMP applications based on the 8051 microcontroller family.
    Web51-C is a migration of the Web51 project that was completely written in assembler, to the C language. The free SDCC or the commercial KEIL C51 compiler can compile the application code.



Available now! You can order Charon I module only or complete Charon I DK above-mentioned.

We have a minimum of 20 pcs in stock all the time. It can be shipped via FedEx next day all over the world. Download the Orderform, fill it and fax to our fax number. If you'll pay by CC, you can have samples on your table in up to 5 days!

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 .  

Device type - Ordering ID

You can order the Charon I module in some variations under following table. For non-preferred types, you should expect long delivery time.

You can see these products in our pricelist and have it up to 3 days on your table..
OID Device type
600 066
End of life
Charon I DK set - (product photo)
Recommended starting set:
 - Charon I [600065]
 - Charon I DK board [600070]
 - DB9 ProLong cable 2m [600064]
 - Manuál, CD
600 065
End of life
Charon I (product photo)
Stand-alone module only
600 067
End of life
Charon I E (product photo)
Special module version with RJ45 connector and Eth. transformer - for high volumes only!
600 070
End of life
Charon I DK board
Just CH1 Development Kit board, 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)
600 069
End of life
Ch1 Hyperion Unit (product photo)
Module Charon 1 in base board and metal box..



Charon I Development Kit

  • The Charon I module with MAC address and serial number on the label. 
  • The Charon I Development Kit
    Simple one side routed PCB only, recommended for your first applications..  
  • The Serial cable for connection the Development Board to the PC.
  • CD with all necessary software (include Virtual Serial Port) in the /Charon1/ directory and all printed manuals.
  • There is no power adaptor included in the standard version, you can use any power DC adaptor 8 .. 15V / 250 mA.


Ch1 Hyperion unit

This is HW group's baseboard & metal enclosure for the Charon I or Charon 2 modules. If you are interested we can send you board scheme and the enclosures mechanical dimension for use in your designs.


The following peripherals are used on the board:

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

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: Do I need to program CHaron I if I need only a simple RS-232 (TTL) to TCP/IP or UDP/IP gateway?
Answer: NO, just use the Conterter FW and set up the necessary parameters, there is no need to program anything!

Question: Will this FW work with the Virtual Serial Port under Windows?
Answer: YES, the Converter FW for Charon I fully supports all the HW VSP functions over TCP/IP. If you enable NVT (using RS-232 Setup, UDP Config, or TCP setup), it supports full RFC2217.

Question: Can the binary inputs and outputs be used along with the serial port?
Answer: YES, but both are controlled using one TCP/IP connection. The I/O pins control in Converter FirmWare for Charon I is realized sending special commands to the serial port data flow.

Question: Can the Charon I firmware be modified?
Answer:  YES, you can use any 8051 family tools. Our applications are programmed in our own development system.
- Web51 (TCP/IP a UDP/IP, the code is written in assembler using GNU binutils linker, many examples available)
- Web51-C (UDP/IP only, the code is written in ANSI C, using SDCC or Keil uC compiler, SNMP examples, doesn't use operating system)
According to x51 platform limitations, we recommend the Charon 2 module for advanced programming.

Question:  What are the Charon I module limitations?
Answer:  The HW solution can be used freely, but the .HEX file with firmware is only for Charon I modules and is protected, so that in will not run on another hardware. If you need to create your own application, use the free or paid Web51.

Question:  Will there be a 100 Mbit Ethernet for Charon I?
Answer:  NO, but we are working on Charon 3, which is based in the Charon 2 module and supports 100 Mbit Ethernet..

Question: What is the difference between "Charon I E" and "Charon I"?
Answer: Charon I E is the same module, but the PCB in version E in longer nad contains Ethernet transformer in the RJ45 connector, which is connected on the main board in the basic version.

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.

Similar or related products

  • Project Web51 -  
    Write your own TCP/IP od UDP/IP application to the Charon I module (8051 MCU) in ASM.
  • Project Web51-C
    Development kit for creating embedded Ethernet UDP and SNMP applications based on the 8051 microcontroller family.
    Web51-C is a migration of the Web51 project that was completely written in assembler, to the C language. The free SDCC or the commercial KEIL C51 compiler can compile the application code.
  • Charon 2
    It's pin compatible embedded module running RTOS and TCP/IP stack. It's programmed in the ANSI C with using the Ethernut project (
  • PortBox - Ethernet / RS-232/485/422 converter
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  • Eth. I/O Controller - Remote binary I/O pins control + RS-232 converter
    Conversion of a serial line to Ethernet and vice versa (Server or Client/Server mode) with RS-485 support and protocol enhancements. Data is transmitted over the Ethernet using the TCP/IP or UDP/IP protocols.