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Making My Own Hart Communicator
i would like to build my own HART communicator form sctrach. i can easily get a 4-20mA signal on which a FSK signal rides. but the issue is what are the commands to access the HART enabled trasnsmitters?

as i stated , i have no idea what are the commands needed to communicate with the HART transmitters , like requesting for equipment id , changing the URV etc.

i searched a lot on the net and the closed i could get was that the commands are transmitted based on DDL language. but how do i program it? and moreover where do i program it ?

i have seen the analog device's AD5700. this is my final year project . so any help would be welcomed.

You are aware that there are commercial chips that do the heavy lifting of analog and FSK signal processing.

It's the specfication documents that tell all about the protocol details. The current HART 7 specifications are for sale on the HART foundation web site.

The HART protocol has evolved and been enhanced over the years and someone might have posted an earlier protocol spec, like HART 5, on the web somewhere. At one time in the distant past, I thought I ran across a hefty (250 page) document 10-12 years ago on the details of HART, but if I saved it, I can't find it. But you might luck out and find one of the older specs on the web.

There is a turn-of-the-century (boy do I feel old writing that) paper by Analog Services, About HART, but it covers more on the HART signal than on the protocol. (remove any space characters the forum inserts into URL)

I just stumbled across a scanned copy of HART Field Communications Protocol, A Technical Overview, 2nd Edition, 1999 on Rosemount's site, of all places. It's about 90 pages long and has lots of specs.

or here (since the forum inserts spaces into long URLs)