HART: Evolution in action

27 May 2020

Wally Pratt, director of HART technology at FieldComm Group, brings us up to date with developments of the HART Communication Protocol.

According to ARC research, as of 2018, the HART installed base represents over 60% of all field devices and over 90% of installed smart field devices – nearly 50 million units.  One of the key reasons that HART continues to dominate today is a constant focus on enhancing the technology in response to evolving market requirements.  

FieldComm Group’s HART technology working group will release Revision 7.7 of the standard this summer and this will include both clarifications and corrections along with enhancements to further optimise the protocol and add targeted useful features.

Major improvements to HART-IP are included in this release. Since its inception HART-IP has supported both field devices and I/O Systems (Remote I/O and WirelessHART Gateways). HART-IP enabled products have been shipping since 2009.   
With the emergence of initiatives like IIoT, Industry 4.0, and the NAMUR open architecture, interest in high-speed Ethernet to the plant floor is increasing.  Ethernet-APL, a 2-wire, 10Mbs, intrinsically safe physical layer is in development with products expected to be available in the next 18 months. Naturally, Ethernet-APL has driven growing interest in HART-IP enabled field devices. But like any ethernet protocol, security must be present and reliable. Notable among the enhancements included in Revision 7.7 are improvements to HART-IP security.

Security improvements
HART-IP has always mandated manufacturers support/supply security in their products. However, the minimum acceptable security suite was not specified. With revision 7.7, requirements for specific, minimum security suites are now specified. There are three legs to security specified – communication security, audit logs and syslogging.

Communication security requires new devices support the industry standard Internet Protocol (IP) Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) suites. Since TLS and DTLS both have many options and choices, their application to HART-IP are tailored and clarified in HART-IP requirements. In addition, HART Commands have been added to simplify security deployment. 

Additional diagnostics and forensic requirements are also included. Devices are required to capture ‘Audit Logs’ that summarise communications activities. There are general security status and records for each client session (up to 128). Client session records include: client identification, connection start/stop times, whether the device configuration was changed in that session, etc. Audit Logs are useful in determining (for example) who and when an inadvertent change to the device was made.

HART-IP devices also must support ‘syslogging’. Syslogs are an industry standard means of publishing device events (to a network's Security Information and Event Management (SIEM) system. All HART-IP devices must support network time (using either NTP or PTP). Consequently, all syslog messages from all network devices are time synchronised, enabling forensics on network-wide behaviour and activities.

Combining communication security, audit logs and syslogging results in robust security for HART-IP enabled products.

Developer kit
As low-cost, 2-wire, Ethernet enabled solutions for field instrumentation near market availability, FieldComm Group is releasing a developer kit to enable field instrument manufacturers to learn about migrating from 4-20mA + HART to HART-IP. Based on the popular Raspberry PI (3B+) system, and using GitHub repositories, the HART-IP developer kit provides a path for process instrumentation manufacturers to prototype and demonstrate high speed HART-IP instruments with minimal engineering effort.  

Initially configured to work with power-over-ethernet POE solutions, the developer kit features a replaceable Ethernet module that will be upgraded to support 2-wire Ethernet-APL as components become available later this year.

Quality assurance
Finally, for developers, new releases of the HART and WirelessHART Tests systems are available. Two important new features are included in these releases: easier to use burst message testing and elimination of the need for commercial gateways when testing WirelessHART devices.  For users, this means improved operation of registered HART and WIrelessHART instruments.

In summary, FieldComm Group’s HART technology working group, along with FieldComm Group engineering staff continue to develop and enhance HART specifications, developer tools, and product registration tests that assure a positive return on end user investment in HART technology for the foreseeable future.


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