I would like to implement the HART protocol and am searching for specifications of the protocol.
I found that the Hart Communication Foundation manages the protocol and on this page it says that

The HART Protocol was developed in the mid-1980s by Rosemount Inc. for use with a range of smart measuring instruments. Originally proprietary, the protocol was soon published for free use by anyone, and in 1990 the HART User Group was formed. In 1993, the registered trademark and all rights in the protocol were transferred to the HART Communication Foundation (HCF). The protocol remains open and free for all to use without royalties.

However when I try to download the documents from the same site it only gives me the TOC so I'm a bit confused.

  • Any idea where would the protocol documents be available?
  • If users have had previous experience in implementing this protocol, I would love to hear about their experience.

On the web site it also says

HART Protocol Specifications

The HART Protocol Specifications (HCF_KIT-13) are sold as a collection of over 15 documents that specify the different aspects of the protocol and test procedures for slave devices. The specifications are sold as a kit that include all the documents in the specification set. The cost of these documents is $975.

The royalty free bit just means that you can sell the devices without having to pay a royalty or licence fee for the privilege. You just have to buy the specifications.

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    \$\begingroup\$ Holy freaking smokes. No way around this, is there? Is this price range common for comm. protocols? \$\endgroup\$ – tyblu Nov 23 '11 at 16:51
  • \$\begingroup\$ @tyblu With the CAN protocol, you have to pay for the specification, and pay a fee for every device you make. \$\endgroup\$ – W5VO Nov 23 '11 at 17:27
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    \$\begingroup\$ That's less than two days of wasted professional effort. But if you are doing this just for your own curiosity, you might be able to learn enough from implementations, for example maxim-ic.com/app-notes/index.mvp/id/4676 \$\endgroup\$ – Chris Stratton Nov 23 '11 at 18:10
  • \$\begingroup\$ I also found this seems to be the Hart protocol description. Is this the complete protocol? @ChrisStratton does the Profibus and Foundation-Fieldbus protocol follow similar pricing/licensing strategies, or are they available for free?? \$\endgroup\$ – Kevin Boyd Nov 24 '11 at 11:25
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    \$\begingroup\$ @W5V0 that is incorrect, CAN licensing does not work like that. \$\endgroup\$ – BullBoyShoes Nov 24 '11 at 12:47

Its correct that the official HART specifications are available from only the HCF, and to be a member its going to cost you (or your company) at least four figures.

Instead, to get a thorough understanding of HART I recommend the HART Technical overview book by Romilly Bowden, available for about $60 from the HCF here:


We constantly use this as a reference when dealing with HART devices.

As a side note, we recently developed a fully embedded UART-HART modem, PM me if you would like to know more ;-)

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  • \$\begingroup\$ To implement the Hart protocol for commercial apps, do I need to be a member of the HCF or do I need to purchase the official protocol from HCF. Can I implement HART by reading and understanding web resources like the one indicated by Chris Stratton? \$\endgroup\$ – Kevin Boyd Nov 24 '11 at 14:11
  • \$\begingroup\$ You dont NEED to be a HCF member to commercially sell HART-enabled products, but you do if you want to use their logos for marketing and get yourself listed on their site. As for the 2nd question... I dont know, can you? Certainly its possible, give them a read and see what you make of it \$\endgroup\$ – BullBoyShoes Nov 24 '11 at 21:47

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