CN0328 describes how to use a multiplexer to transmit HART data on any of the 4 output channels of the AD5755, but how would one reliably _read_ the HART data from all 4 of those channels? Is it possible to switch the multiplexer across all 4 channels faster than the HART preamble arrives? Even if you could do that, would getting a partial preamble still allow you to read the rest of the data reliably? I am wondering if there is the possibility to "scan" the 4 channels like a radio scanner, then lock in on the one that is transmitting?
I'd like to direct your attention to a new design that is similar to the CN0328. The CN0418 is an update to that design complete with open reusable embedded source that you can look through to see how the HART receiving is done. There is a larger system example, the CN0435 ,which also might contain some clues to what you are looking for here.
I'm not sure our examples show any 'scanning' like applications, but it seems this is possible, it's likely some software work.