[Elecraft] Passing Band Data from [KX3/KXPA100] to [KAT500/KPA500]

[Kevin McQuiggin]

Hi All:

I have the setup as described in the subject line.  My KXPA100 is interfaced to my KX3 using the short Elecraft CAT5 cable.  I have recently added a KPA500/KAT500 combo.

I noted from the manuals that the [KX3/KXPA100] must really be treated as a generic external transceiver, and the two “blocks" [KX3/KXPA100] and [KAT500/KPA500] do not communicate digitally, but are interfaced using a simple PTT line.

This is fine, and what I expected when buying the combo.  

It would be nice, however, if it is possible, to allow the band and other data sent by the KX3 to the KXPA100 to be extended to the other block, the [KAT500/KPA500].

It is this aspect that I am currently investigating.  I have the connector pinout for both “blocks” and note that the [KX3/KXPA100] block utilizes serial transfer of data between them, where the second block [KAT500/KPA500] utilize essentially BCD for band data and an “AUXBUS” signal that I have not yet found out much about.

As an experienced hardware/firmware/software person I am thinking that it might be possible to extend communications between the two blocks (and all four devices) using an interface such as a microcontroller of some sort.  

My questions:
Are my assumptions regarding the lack of connectivity between the two blocks correct?  [I think so, based on interconnection details in the manuals]
Has somebody built such an interface already?
Is there information available on message passing and protocols between the K3 and [KAT500/KPA500]?  The K3 is used as the reference, as the KAT500/KPA500 are designed to tightly integrate with it.
Same protocol question for the KX3/KXPA100.

Essentially, what I would be looking to do is to use a microcontroller to emulate a K3 in order to talk coherently to the [KAT500/KPA500] block.  Then the other side of this interface would talk [KX3/KXPA100].

My apologies if this a RTFM question or documented somewhere, but if so, I could not find it!

73,

Kevin VE7ZD