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I/O Controller PL: Control I/O & Serial port over Telnet

Warning: Produkt is replaced by a new version: I/O Controller2

I/O Controller is a unit containing 8x digital input over ethernet, 8x digital output over ethernet and RS-232/485 serial (Terminal server) interface. All the interfaces are accessible over a network using the M2M (Machine to Machine) protocol on TCP/IP.

Two devices can be connected to each other (the Box-2-Box mode), digital signals and RS232 can then go back and forth across the network.

The I/O Controller contains:

  • 1x RS-232/485 (Terminal server, virtual serial port)
  • 8x digital input
  • 8x digital output

The product can not only be a "TCP Server", but also can act like a "TCP Client/Server". This means, when your digital input value changes, IO Controller connects to the server via TCP/IP and sends a 7-byte information packet about the input change over the M2M (Machine to Machine) protocol.

The RS-232/485 serial port can be connected to your PC's virtual serial port using the HW Virtual Serial Port software, the remote digital I/O can be dirrectly controlled from this software.

We provide you with the sourcecode of routines written in MS Visual Basic, Delphi, Borland C++, JAVA, PHP and others to facilitate your implementation of the IO Controller into your system.


I/O Controller

Big product photos: 1 2 3 4 5

Basic features

  • RS-232 or RS-485 serial port accessible over Ethernet or as a COM5 in windows (HW Virtual Serial Port) .
  • 8 digital inputs to connect contacts, buttons, or 7 to 24VDC
  • 8 digital outputs (open collector)
  • Virtual serial port driver for Windows = easily get e.g. COM 5 on your PC

  • The inputs and outputs are controlled over a M2M (Machine to Machine) protocol. They can be controlled directly from a windows software (see examples), WWW page (PHP / Java) or from the HW VSP software (Virtual Serial Port)
  • 2 I/O Controller's can be connected to each other, so they can "tunnel" a serial port + 8x Ethernet input + 8x Ethernet output.
  • Ethernet interface for connecting to an IP network
    • Telnet-like M2M protocol
    • Support for TCP Server and TCP Client/Server modes
    • Box-2-Box mode

Typical applications

A typical application is remote access to a RS232 or RS485 controlled technology. I/O controller is an ideal device if you need remote digital I/O signalizations (ethernet input, ethernet output), remote relay control, server accessible remote inputs together wirh a RS-232 or RS-485 bus for a bar code reader, display, etc...

You can access the device using the HW VSP software, or you can write your own software using our wide examples and source codes library.

Input over ethernet, remote relay control, digital i/o, ethernet i/o, remote i/o, remote control, industrial i/oApplications examples

  • Remote control of technology over RS-232 and RS-485 bus
  • Remote control of displays and signalling
  • Remote reading of PIR sensors, door contacts and security systems
  • Remote relay control
  • Industrial I/O
  • Card readers, RFID readers
  • Sales machines
  • Security alarms
  • Attendance systems
  • UPS controll and logging
  • Bar code readers


Example applications

Here are some more detailed application exapmles:


Input over ethernet, ethernet input, ethernet output, TCP client/server, digital i/o, terminal server, remote controlTypical wiring




  • Software for Users
    • Hercules - configuration (IP address, Telnet setup) and testing utility for Windows
    • HWg IPRC cmd – command-line control of outputs
    • HW VSP - HW Virtual Serial Port for Windows.
      I/O Controller is also supported by the VSP Multi version that allows you to connect up to 64 serial ports to a single PC.
  • For programmers
    • Examples in the HWg SDK
      SDK (Software Development Kit) with examples of controlling the I/O Controller is available for download free of charge.

      • EX01: UDP Setup (Borland C++ Builder, MS Visual C, VB, Delphi, C#)
      • EX02: I/O Controller (Borland C++ Builder, MS Visual C, VB, Delphi, C#)
      • EX03: Control Remote Serial Port (Borland C++ Builder, MS Visual C, VB, Delphi, C#)
      • EX13: TCP Setup (Borland C++ Builder, MS Visual C, VB, Delphi, C#)
  • NVT (Network Virtual Terminal) M2M communication protocol


System topology

Here you can see a typical I/O Controller system wiring and protocols.
digital input, digital output, Input over ethernet, remote relay control, digital i/o ethernet, rs-485, TCP client/server, remote i/o, rs-232, terminal server
  • TCP/IP Server   [Client -> Server]
    The I/O Controller waits as a TCP server until any side (PC or server) opens a TCP connection. When the connection is established, the internal buffered data is sent and then the device allows communication as a standard "terminal server".
    The digital I/O (digital inputs and outputs) can be controlled over a M2M (Machine to Machine) protocol using the extended RFC2217, but only if NVT support is enabled.

  • TCP/IP Client/Server    [Server <- Client]
    The I/O Controller received serial port data into its internal buffer and tries to send them to the server. It will try to open a connection to the preset IP address and port. If the attempt was unsuccessful, it waits for a second in the TCP Server mode and then tries to open the connection again.
    The digital I/O (digital inputs and outputs) can be controlled over a M2M (Machine to Machine) protocol using the extended RFC2217, but only if NVT support is enabled.

  • UDP/IP
    The data is transferred in UDP packets, with no delivery notification. The portbox uses a sophisticated "Packetizer", which allows various conditions of what can and what cannot be send from the serial line to Ethernet.
    The remote ethernet I/O (digital inputs and outputs) cannot be controlled in the UDP mode..

  • VirtualSerial PortVSP (Virtual Serial Port)
    You have a HW VSP software which creates a virtual COM port under Windows OS, so that the device acts like it's connected directly to your PC, though it's a virtual remote port. If the buffer is enabled and the TCP connection is not available, the data is stored into the internal buffer memory.
    The remote ethernet I/O (digital inputs and outputs)
    can be controlled from the HW VSP software in the "Binary I/O", tab, if the NVT support is enabled.


Technical specifications

Digital Output  
+ Output type 8x darlington transistors with common ground
+ Max. output Voltage up to DC 50V
+ Max. output Current up to 500 mA / 1 pin
max. total Power Dissipation = 1W / 1 pin or 2.25W all pins
+ Inductive loads suppression 8x integral suppression diodes for inductive loads - COMMON pin
+ Power up init value Power up init value is on the output up to 1ms after power-up
+ SW control Binary outputs are controlled over NVT protocol through TCP/IP
Digital Input  
+ Input type Binary optocoupled
+ Log. 0 voltage 0 .. 3V
+ Log. 1 voltage treshold / “on” current from 5V / 5mA to 20V / 25mA
+ Max. input Voltage and Current up to 40V / 50 mA / 1 second
+ Isolation Voltage max. 50V to power supply
+ Sampling period 10 ms
+ SW control Binary inputs are controlled over NVT protocol through TCP/IP
Serial port  
+ Data bits 7 or 8 or 9
+ Stop bits 1 or 2
+ Parity None / Odd / Even / Mark / Space
+ Baud rates 50 .. 115.2 kBd - whole range, step = 50 Bd
+ Data flow control XON/XOFF, CTS/RTS, None
+ Interface RS-232: 1x DB9M (RxD,TxD,RTS,CTS,GND) - DTE device
RS-485: 1x DB9M (A, B)
+ Used RS-232 signals RxD,TxD,RTS,CTS
- DSR pin is used for setup mode activaton only
+ Used RS-232 internal buffer memory 740 B for incoming data, 740 B for outgoing data
Ethernet port  
+ Interface RJ45 (10BASE-T)
+ Compatibility Ethernet: Version 2.0/IEEE 802.3
+ Supported protocols IP: ARP, TCP + NVT (Network Virtual Terminal)
+ TCP connection closing Data - timeout 50s  (with support of NVT - ACK/NOP)
Environmental conditions  
+ Operating temperature 5 – 50 °C
+ Storage temperature -10 to 85 °C
+ Humidity (non-condensing) 5 to 95 %
Physical parameters  
+ Power supply requirements 8-24V/ Typically 250 mA DC
- barrel (coaxial) power connector, GND on the shield
Binary I/O lines connector - Cannon 37 Female (37-pin sub-d socket) or
- 20 pins on screw terminal strip
Functional parameters  
+ Device SETUP configuration options RS-232 Setup - over any RS-232 terminal
TCP Setup - over TCP/IP - any telnet terminal on the TCP/IP 99 port
UDP Config - network parameters via UDP using the Hercules.
+ LED diagnostic LINK and POWER
-LEDs are inside the RJ45 Ethernet connector or LINK LED is next to Ethernet RJ45 connector.


digital input, digital output, Input over ethernet, rs-485 ethernet input, ethernet output, remote i/oI/O Controller's inputs
All 8 digital inputs are optocoupled with common ground on IGND pin. You need to connect this pin to the GND pin on your connector. You can also control the pins using contacts which are connecterd to the POWER pin. The maximum power drain is 200 mA!


I/O Controller's outputs
The digital outputs are realized with eight open colector transistors, which have protecting diodes connected to the "common" pin. This pin should be connected to the positive pole of the following components (for example relays), this will protect the pins against voltage peaks.

Built in RS-485 support
The I/O Controller handles the RS-485 line similary to the PortBox - Revision 1 device, details can be found in the datasheet, or in the PortBox description.


Possible device extensions, coming soon...

digital input, digital output, remote relay control, digital i/o ethernet, terminal server, remote controlThe following options will either be implemented in the following firmware version, or in the next device version.

  • M2M (Machine to Machine) protocol extension: WWW pages and other interfaces (SNMP, WWW, XML, Modbus/TCP) are implemnted in the Damocles device, which we are working on.
  • Built-in 4x Ethernet port 10/100 Mbit switch Ideal for applications where you don't have enough free Ethernet ports or cables, or you cannot use a stand-alone switch or hub - customer solution.

Questions and comments

If you are interested in any of these modifications, need help implementing them in your projects, or if you want a specific customer solution, feel free to contact us


Built-in I/O Controller version - Charon I module

Charon1 - digital input, digital output, Input over ethernet, digital i/o ethernet, remote control, industrial i/oThe I/O Controller box can be replaced with a module version, which looks like a big integrated circuit and can be placed on a printed circuit board of a customer solution.

The Charon I module contains a similar firmware. Digital inputs/outputs are combined in one 8-bit port. You can use setup to control which pins are outputs and which pins are inputs, or you can set all the pins as output or input.

The Charon I has 24 pins and measures approx. 34x42 mm (2x12 pins with 100 mil diameter). You only need to place a supplied transformer and a RJ45 connector outside the module.  

The Charon I module is an ideal solution for you application if it works with PortBox or I/O Controller.



Useful SW

  • Hercules - Input over ethernet, remote relay control, TCP client/server, terminal server, remote controlHercules SETUP Utility
    When testing the I/O Controller device, the "Test mode" tab in our Hercules SETUP software can be quite useful. In the "test mode", the software highlights the NVT commands, you can send and write the commands in the HEX form.

  • HW Virtual Serial Port - ethernet input, ethernet output, ethernet i/oHW Virtual Serial Port
    A virtual serial port driver is a software tool which creates an imaginary serial port in the windows system, for example COM5. This data is then redirected to another hardware device.

Examples with sourcecode showing how the I/O Controller can be used

  • digital input, digital output, ethernet i/o, remote controlBorland C++ communication example
    A simple communication example with a TCP/IP device in Borland C++ Builder 6.00. The example demonstrates a simple Client terminal and basic NVT commands (Network Virtual Terminal) = Are You There and I/O functions.
  • Input over ethernet, remote relay control, ethernet i/o, remote i/oDelphi Charon 1 - NVT communications example
    A simple communication example with a TCP/IP device in Borland Delphi 5 demonstrates a simple Client terminal and basic NVT commands (Network Virtual Terminal) and ethernet I/O functions.
  • Input over ethernet, digital i/o ethernet, remote i/o, inrustrial I/OMS Visual Basic example
    Simple routines for NVT commands with a TCP/IP device over Winsock in MS Visual Basic 5.0. Simple commands for remote pins control are implemented, TEA is not.
  • ethernet input, ethernet output, digital i/oJava NVT simple Code Example
    A very simple remote I/O pins control in a JAVA application. This application is not password protected, so you can modify it to suit your needs.
  • Input over ethernet, remote relay control, digital i/o ethernetPHP I/O Controller example
    A very simple digital I/O pins control. The user requests a WWW page from a PHP server, which opens a connection to a predefined IP address and port and reads the values.

  • ethernet input, ethernet outputLabVIEW driver for the I/O Controller
    The german company MJH Software sells a driver which you can use to control the device from DASYLab and LabVIEW. You can find the details on their website, here is a screenshot from the tested application.

  • Tom Boyd from the (server for the SW developers and schools) tested IO Controller and updated our original Delphi application.. (sw screenshot: I/O Controller Excerciser / SW download ).


NVT (Network Virtual Terminal) protocol description

terminal server, remote controlThe NVT (Network Virtual Terminal) is a complicated protocol when used with a standard server. In our applications we use only simple fragments of NVT, which are asy to understand. We use commands in a TCP/IP stream, where every command starts with a „FF“ character. If you need to transmit the „FF“ character (255 decimal), the transmitter must double it, otherwise the following data will be considered as a command. Because of this, the NVT can be turned off, or both sides of the communication must respect this.



FAQ & Support

Ask for the price or details:
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Q: How long does it take to deliver a packet containing the input-change information?
A:  This time cannot be exactly defined over a standard network, because it depends on the network traffic, etc. But the I/O Controller tries to setup the connection and send the data as fast as possible according to the network specifications. Practically it might take 15-25ms to deliver the packet even on high traffic networks. If the system also tries to set the output state, the reaction time will be 20-40ms.


Q: Does the I/O Controller send information to the TCP server about digital input's change or whether there is any data received over the serial port?
A:  Yes, there are two such situations:
a) A TCP connection is established - A digital input's change is signalled with a NVT sequence containing a new value of inputs.
b) A TCP connection is closed - If the device works in the "TCP Client/Server" it will try to establish a TCP connection and send the data in a NVT sequence. If if fails establishing a connection, the inputs change is not buffered or stored.


Q: If I connect 2 I/O Controllers to each other, as described on page 27 in the datasheet, can I read the inputs from a PC?
A:  No, the I/O Controller only supports one TCP/IP connection at a time.

Q: Can we use one I/O Controller device from different PC in one network?
A:  Yes, but not in one time - You can connect from PC1, send the command Read/Write values, device confirm it and you close TCP connection.
It takes around 20ms or deal time, than you can do the same from another computer. This mesna, that there is limit of One TCP Connection in one time only.

Q: How to secure I/O Controller against hackers?
A:  You need to spend some time building up you network's security, the standard is a firewall separated Ethernet network. The device can be setup to respond only to requests from a certain IP range, outside this range it wil not answer even if only pinged. You can also use TEA (Tiny Encription Algorithm) for client authorisation. If you use TEA, the password is not transfered via the network.


Q: What is a packetiser ?
A:  Packetiser is a group of conditions, controlling the RS-232 to Ethernet packets algorithm. In the TCP/IP mode, the packetizer is controlled only with a "Serial line timeout" parameter, which defines a length of space after the last received character before creating and sending a packet.


Q: We want to use our own software to control the device, are there any SW examples or libraries?
A:  Yes, please look at our Support & Download page, where you can download many examples for Borland C++ and Delphi.
We even have very simple examples in Visual Basic, JAVA and PHP.


Q: We need this device to control a 230V device. Do you have a version with such outputs?
A:  Yes, but regarding to different power parameters in different countries and price of the certificationhneeded, we mostly recommend to place the I/O Controller to a DIN molding together with a relay. You can e-mail us, if you have further questions.


Q: How does the RS-232/485 work? Is there a RS-422 version available?
A:  Yes, the I/O Controller is basically an expanded PortBox (RS-232/485 - Ethernet Converter), You can choose between RS-232 / RS-485 using the DIP switches. For the RS-422 and external unit is needed.


Q: The PortBox (RS-232/485 - Ethernet Converter) can be controlled via the virtual COM port for Win 2000 and XP. Can this be used for I/O Controller?
A:  Yes, you can not only control the the RS-232 line from the Virtual COM port, but since version 2.19b also the digital inputs/outputs.



The products are on stock and we can send them worldwide with FedEx and other couriers. The price can be found in the pricelist. In the Czech republic, you can also order using our eshop -

I/O Controller set

Input over ethernet, remote relay control, digital i/o ethernet, ethernet input, ethernet output, digital i/o
  • I/O Controller PL [600291] (photo)
  • DB9 LapLink cable 2m [600063]
  • 1x Power adaptor "wall plug" - [600 080]
    You can change the type of the adaptor to UK or USA version, note this in your order
  • I/O Controller Test board [600032]
    8x LED (outputs) and 8x DIP (inputs) on a small PCB - detailed image
  • Printed datasheet - "I/O Controller "
  • CD with documentation, FirmWare versions, testing utilities and other SW

-> Order 

Ordering versions

The I/O Controller can be supplied in several versions, according to the bellow described ordering number. If you do not specify a device version in your order, we will send you a prefered type. The delivery terms of the non-prefered types should be verified by phone or requested in your order confirmation.

OID Device types
600 292
I/O Controller PL set (photo)
Recommended starting set, it contains:
- I/O Controller PL [600291]
- 20 pin connector [600 034]
- EU Power adaptor [600080] (can be replaced by UK or USA type)
- I/O Controller Test board [600032]
- DB9 LapLink cable 2m [600063]
- Manual, CD
600 291
I/O Controller PL (photo1, photo2)
I/O Controller PL device unit, one set of connectors [600 034] "20 pin connector" attached in package
600 295
Wall mounting profile "C" size (photo)
600 301
Dual Lock fastener (photo)
600 025
DIN Rail box fastener (product photo, aplikace: photo1, photo2)
600 307
I/O Controller 1204 (photo)
Special version of I/O Controller 1204 with 12 Inputs for Dry contacts and only 4 outputs. Terminal connectors included.
600 026 I/O Controller - Terminal Block version (photo)
Industrial version in metal robust box
600 030 I/O Controller set (picture of the set)
Recommended starting set of industrial version in metal robust box
600 028 I/O Controller - Cannon 37 (pictures)
- (Warning: old type, use another..)
600 027 I/O Controller - PCB only (Terminal Block)  
- (Warning: old type, use another..)

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