The XTB-232 conversion has turned out to be both simpler and more complex than anticipated.
Simpler because there is no handshaking with the computer. It receives an X10 command and just fires it off to the computer at 19.2Kbaud, so that takes place in the half cycle after the command is recognized. The SmartHome protocol just assumes the computer is ready to accept it whenever it is sent, and that it receives it correctly.
More complex because the XTB-232 was built for the CM11A protocol, which handshakes with the computer to establish communication and verify data was transferred correctly. This process can take seconds when the computer is in standby, and the code is set up accordingly. So all of that must be eliminated.
Also more complex because there is no handshaking on incoming commands, so it must be ready to receive a burst of serial bytes anytime, regardless of what else it is doing.
The XTB-232 is set up to both receive and transmit extended commands. Nothing in the SmartHome protocol supports that, so extended commands will be ignored. I may include an option to turn a preset dim command from the computer into an extended dim command with reduced resolution to allow it to work with Leviton dimmers.
I still need to know what the Harmony does at powerup to verify it is connected to the IM.
Also, is there a problem if the Harmony receives an upload for each half of the doublet? Does the second serial transmission have to be suppressed when both halves of the doublet is received? ( A1, A1, A_ON, A_ON.) If so, I assume it would still need every bright and dim command in a sequence.
Jeff