The CM15A is X-10's latest PLC interface, introduced in late 2004. It incorporates a 310MHz RF receiver, a 310MHz RF transmitter and a two-way PLC interface. It connects to a PC using USB instead of RS-232. Physically, the CM15A is about one inch wider and one inch longer than the CM11A and lacks the feedthrough outlet that was on the CM11A.

The RF components are third party daughterboards that appear to be from Keymark in Taiwan. The receiver is a single chip superheterodyne ASK receiver (HiMark RX3310A). The receiving antenna is external to the case. While it is insulated, that appears to be for cosmetic reasons as the RF receiver and antenna lead are isolated from line voltage by the step-down transformer used in the CM15A power supply. If needed, it might be possible to improve RF reception with a more efficient, remotely located (and even preamplified) antenna. Use 50-ohm coax between the remote antenna and CM15A. Adding a wideband preamp to the remote antenna will further improve reception.

The RF receiver is tunable but it might be simpler to replace it with one of the desired frequency.

The transmitter uses a SAW resonator. The transmitting antenna is merely a short length of insulated wire looped around the interior of the enclosure. X-10 software only uses the transmitter for the Ninja and Vanguard camera mounts. Replacing the transmitter or adding another of a different frequency (e.g. to control a ceiling fan) should be possible although control requires replacing the Cypress controller.

Aside from the microcontroller, the PLC circuitry appears to be the more or less the same as in the CM11A. An ESM1 indicates about 5-6Vpp PLC output which is a bit better than the CM11A. The ACT Scope-Test2 shows that the CM15A outputs on all three phases with a level (at least on two phases) which is both slightly higher (6Vpp) and more stable than the CM11A.

The microcontroller is the Cypress CY7C63723-PC USB-PS/2 Peripheral Controller. It has 10 DIO pins. X-10 is using its internal 6MHz oscillator. (NOTE: X-10 uses this same chip in the ATI Remote Wonder, Lola and CM19A.)

Tests with other RF transceivers active indicate that the CM15A ceases transmission upon sensing a collision and then retransmits after the powerline is clear. Tests used a TM751 on the same phase and on opposite phases. Tests were repeated (on one phase only) with an RR501 and Leviton HPCRF as the second transceiver. All combinations lead to duplicate PLC commands in response to RF codes but with no corrupted commands (aside from any initial collision). The details differ depending on the second transceiver. With only the CM15A active, there are no duplicate commands.

CM15A Schematic

Below are several oscilloscope screenshots showing the CM15A lines for X-10 INPUT and AGC RESET.

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