TwinCAT ADS via serial or HTTP connection enables new applications
Enhancements such as serial and HTTP capability have made TwinCAT ADS a software product which enables horizontal and vertical communication on a wide variety of platforms. TwinCAT ADS is a modular software component which is part of the Beckhoff proven TwinCAT real-time PC based control software line. TwinCAT ADS is the modular software component that handles message exchange between all the TwinCAT software modules including the TwinCAT IEC 61131-3 PLC and the motion control blocks which are part of the NC module. Messages are exchanged between the individual modules by the TwinCAT message router through the uniform open ADS (Automation Device Specification) interface. The router manages and distributes all the messages within the local system and to remote TwinCAT devices via TCP/IP. The advantage of this solution is its flexibility: ADS enables horizontal and vertical communication on different platforms. Beckhoff offers ADS components for the Windows NT/2000/XP operating systems and for various CE systems (ARM, X86, MIPS, SH3, SH4) free of charge. They can be used in different programming environments such as C++, Visual Basic, .Net, Delphi or ASP. The ADS protocol is open and documented. Another option is the implementation of ADS on platforms and languages that are currently not supported (e.g. Linux, Java).
ADS via serial interface
For diagnostic purposes, a PDA is frequently connected to a TwinCAT system via the wireless
LAN network using the open ADS protocol. However the PDA might need a connection
via a serial interface using the open ADS protocol. For serial applications, the TwinCAT
ADS router was extended so the serial COM port can be used for communication in the
lower level ADS transport layer – alongside the existing TCP/IP.
ADS via HTTP
HTTP-based access using the open ADS protocol was also implemented. ADS communication
was already based on TCP/IP making it perfectly designed for local or intranet applications.
For communication via the Internet, firewalls would have to be configured appropriately.
With the extension of the ADS transport layer, “ADS via HTTP” is now available as
a regular interface. The TwinCAT ADS component acts as a HTTP consumer and communicates
with the actual TwinCAT target device via a TwinCAT ADS WebService that is configured
for intranet or Internet. The ADS WebService is used as a converter between ADS HTTP
and the ADS standard.
ADS HTTP communication offers significant potential, particularly for remote maintenance:
Web-based visualization and diagnostic tools facilitate remote service, although the
term “web-based visualization” is often used incorrectly as a synonym for “visualization
running in the web browser”. There is no reason why a HMI application that already exists
locally at the machine should not be run remotely by the service staff. Only ADS data exchange
occurs through the Internet firewalls via HTTP port 80.
There are numerous ADS routing options: The ADS interface for applications such as Scada
systems or the TwinCAT OPC Server is maintained. The ADS router manages the communication
transparently via different transport routes.
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| The function “ADS via serial interface” will be available for TwinCAT version 2.9 from January 2004. Estimated market release of the “ADS via HTTP” option is expected for the 1st quarter of 2004. |
