FAQ

 

Do I really need this?

It sounds like a bit of overkill?

 

Framing messages?

Do I still need to know about formatting HART messages?

 

Sample code?

Do you have sample code to help start communicating quickly?

 

HART-IP

My vendor does not yet support HART-IP. What can I do?

 

HART-IP Server

Do you supply the HART-IP server as a separate product?

 

Smart HART Modem

The Exalon Delft Smart HART Modem is a HART modem with a built-in HART Master that provides HART compliant timing and bus behavior.

Smart HART Modem

Accessing wired HART networks

Traditionally HART networks were connected to PC's using modem dongles that connect to the RS232 port. The modem was powered from the DTR, the data direction (sending / receiving) was controlled by the RTS line and the CD line to indicate a HART carrier signal was present on the line. Over the years a number of developments have occurred that make this approach hard or impossible to sustain.

HART networks are half-duplex

At the end of a transmission the master must switch the RTS line to commence receiving. This must occur after transmission is complete but within a few milliseconds after transmitting the last bit. However, the transmitted message resides in the UARTS FIFO and there is no way to know exactly when the FIFO is done transmitting (depending on UART type and OS version) unless implemented at a very low level. Bursting slaves and secondary masters narrow the time for switching RTS even further.

Unpredictable USB dongles

As most modern laptops don't have RS232 ports, either USB serial dongles are used or HART modems with USB interface. But remember, these devices create a virtual RS232 port, and control of the RTS line and reading the state of the FIFO is commonly buggy or missing all together.

Bandwidth problems

As the size of HART networks grow the 1200 baud transmission rate is becoming a bottleneck. This creates a need for multiplexers that route communication to multiple slaves simultaneously. Available multiplexers use HART over RS485 communication which is not readily available on PC's and laptops and has the same timing issues as mentioned above.

WirelessHART networks need access as well

The growth in traffic caused by the introduction of WirelessHART networks has led to a need for higher bandwidth interconnection gateways. This has triggered the definition of HART-IP or HART over IP Based Networks as defined in the HCF standard HCF_SPEC-085, Rev. 2.0. This standard defines HART communication over UDP or TCP transport layers and can be used to connect to both wired as well as wireless networks. It is now the preferred inter-operable and uniform way to connect to HART networks. This will create significant cost savings for manufacturers of host applications and greatly simplify deployment by end-users.


HART-IP network

Smart HART Modem provides the solution

Exalon Delft's Smart HART Modem solves all of the above problems:

Provides 2 independent virtual COM ports for legacy applications

In this mode the Smart HART Modem automatically generates RTS signaling by detecting the end of transmitted messages. This will enables existing applications that already implement burst mode support but suffer from unreliable USB modems to operate correctly.

Operates as a HART-IP Modem (HART over UDP)

This mode enables applications that already support HART-IP for WirelessHART applications to communicate with a local or remote HART network without worrying about HART bus timing.

Operates as a HART-IP IO-System

The most advanced mode implements bus multiplexing using the built-in 2 independent HART masters. This enables you to partition your network to solve bandwidth problems. Multiple Smart HART Modems can be combined, each adding 2 more IO cards (HART bus interfaces). It can be used with the HART Communication Foundation's HART Server (OPC server) to connect to SCADA systems that not yet support HART-IP.


Exalon Delft Smart HART Modem advantages
Feature Other vendors Smart HART Modem
Simple HART dongle Virtual COM port HART-IP Modem HART-IP IO-System
Reliable USB connection no Yes Yes Yes
Automatic RTS generation by built-in master no Yes Yes Yes
Reliable communication with burst Mode devices no Yes Yes Yes
Dual independent HART channels over a single USB connection no Yes Yes Yes
Unified HART-IP interface no no Yes Yes
Automatic message timing on the HART bus by built-in master no no Yes Yes
Remote clients can connect over the Internet no no Yes Yes
Multiplexes 2 HART channels into a single network (IO system with 2 IO cards) no no no Yes
Expandable number of channels by simply adding more Smart HART Modems no no no Yes
Compatible with HCF HART Server (OPC server) Not with USB dongles in combination with burst mode devices Yes HART 7 slaves only Yes
Works with Linux Depending on the  USB kernel module Linux > 2.6.38 Yes Yes

Best value for money

Smart HART Modem gives you 2 independent HART modems with a single USB connection. And the Exalon Delft HART-IP server is included for free! It is the most trouble free, most universal HART modem on the market today. And cost less than you think.
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Smart HART Modem

What's in the box

  • 1 Smart HART Modem 126 mm x 57 mm x 26 mm
  • 1 pair of test leads
  • 1 USB cable
  • 1 CDROM containing USB drivers for Windows (XP/Vista/Windows7), HART-IP server (Windows/Ubuntu 10.04 LTS), C#/C++ code examples, ActiveX HART Modem Server control (drop-in replacement for the HCF control used by the SDC-625), manual.


FAQ

Do I really need this?

Do you think it sounds like a bit of overkill? Not if you consider the amount of time you can save on support calls. HART is not an extremely difficult protocol to implement. However, it does require relatively accurate timing in modern applications. A personal computer's UART and Operating System are just not well suited to the task. Real Time systems like PLC's are much more suited. The Smart HART Modem contains 2 micro-controllers that are programmed to give tight Real Time control over the UART but at much lower cost then a dedicated PLC.

Do I still need to know about formatting HART messages?

If you are a developer of a HART master application, the answer is yes. The Smart HART Modem will simplify your task, especially if you operate it in HART-IP mode.

Do you have sample code to help start communicating quickly?

We provide sample code in C# to connect to the HART-IP server that will get you up and running in no time. This code will work in MONO too if you prefer to build for a Linux platform.

My vendor does not yet support HART-IP. What can I do?

Your vendor is likely working to implement HART-IP to access WirelessHART networks. When that is done the Smart HART Modem will work for your Wired networks as well. The best way is to contact your vendor to express your need for HART-IP support. You can also drop us a note, so we can support your vendor with the implementation. In the meantime you might want to use the Smart HART Modem in Virtual COM port mode or use the HCF's HART Server (OPC server) if your application can operate as an OPC client.

Do you provide the HART-IP server as a seperate product?

Our HART-IP server operates together with the built-in masters in the Smart HART Modem. This is necessary to guarantee correct timing on the HART bus.