Many of you are familiar with the XTB and XTB-IIR X10 Transmit Boosters that have been available since 2006.  The XTB-IIR includes a digital powerline interface for high-end automation controllers.  The XTB-232 is intended to provide a similar high-reliability powerline interface for PC-based automation systems.

The XTB-232 emulates the CM11A "real-time" protocol, and can be directly used as a CM11A substitute for PC-based automation systems such as HomeSeer and Home Control Assistant.  It does not have a schedule clock, and will not support any controller functions itself, but it will act as a powerline interface for ActiveHome or ActiveHome Pro running on the PC.  It handles all CM11A direct-action commands, but will not accept any downloaded functions such as timed events or macros.

Like the other XTB units, the XTB-232 outputs a much stronger signal than other X10 transmitters.  While not quite as powerful as the XTB-IIR, it can still output over 20Vpp onto the powerline.  When combined with a good tuned-circuit passive coupler like the XPCP, the XTB-232 should provide adequate signals throughout an average home.

Collisions can lock up the real CM11A.  The XTB-232 contains a "polite" transmitter, and will delay its transmission as long as necessary waiting for a clear line if there is already X10 activity on the powerline.  It will also immediately abort a transmission if it senses a collision, and will automatically retransmit that command after the powerline has cleared.  The handshaking defined in the CM11A protocol document ensures the controlling software knows what is actually happening on the powerline.  Since an acknowledgement is issued over the serial port when a transmission is successfully completed, the automation software can reissue that command when an acknowledgement is not received in a timely manner.

The XTB-232 handles all normal and extended commands, including the pre-set dim commands used to set brightness levels in Insteon dimmers running in the X10 compatibility mode.  Just plug it into any standard AC outlet, connect it to the PC with the same cable that attached to the CM11A, and select it as a CM11A in the automation software.  (4800 baud, 8 bits, no parity, one stop bit)  The automation software should recognize it as a CM11A, and function the same.

The LED indicator provides feedback on the state of the unit.  It should glow dim green whenever it is active and monitoring the powerline.  A bright green flash indicates it is receiving a potential X10 command. An orange flash indicates it is transmitting.  Red flashes indicate various errors:  3 for a receiving error, 4 for a collision, or 5 for a problem with the serial data link.

For those of you interested in the programming details, the XTB-232 supports the functions detailed in sections 1-4 and 6 of the CM11A Rev3 Protocol document.  It also responds to the clock initialization and status request commands, but will just return null bytes for data.  Note that the XTB-232 only outputs the zero-crossing signal burst, and is intended for use in homes with a standard 120V/240V split-phase electrical system.  It must be paired with a 3-phase repeater when used in a 3-phase electrical system.

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Please contact me if you have any questions at: jeff@jvde.us
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