[Elecraft] KPA500 serial interfaces

[Andy Durbin]

"The talk of sharing connections with boxes that multiplex over an RS232 connection led me to find the products that speak SDLC to a device that then communicates with a set of RS232 devices. I hardly think that is the same thing, since although a single RS232 is required on the computer, it is not speaking directly to the devices on the other end."

Don't know if this is related to the description of my interface but, in case it was, here is a bit more detail:

I use a relay to switch between 2 different RS232 transmitters.  One is the routine interrogator of the RS232 receiver, the other is switched in circuit when I want to send a non-routine command to the receiver.   The receiver doesn't know where the command came from and it doesn't care.  The routine interrogator doesn't know it was taken out of circuit because the TX line is only stolen in a gap between its routine interrogations.

As an example - I can configure my system so the KAT500 Utility is the routine interrogator of my KAT500.  When I change my TX frequency my controller switches the RS232 transmit source from the PC to my Arduino which sends the KAT500 a new frequency.  That frequency command is in a gap between the routing KAT500 Utility interrogations.    

My interface actually has 3 multiplexing relays  - one for the KAT500 interrogator (KAT500 Util or my interface), one for the KPA500 interrogator (KPA500 Util or my interface), and one for my TS-590 interrogator (OmniRIg or my interface).  

Works perfectly and, to the best of my knowledge, no RS232 standards were damaged.

(I wrote all of that without a single mention of "polling").

Andy, k3wyc