This is a plug-in daughterboard that replaces the Cypress CY7C83723 microcontroller used in the CM15A with a ZX-328n, converting the input/output to RS232. In addition to X-10 PLC send/receive, it provides access to all of the CM15A hardware including the RF receiver and RF transmitter modules and the 2KB EEPROM. The CM15A schematic can be found here. It will report all X-10 RF (standard and security) and, if the superheterodyne RF receiver in the CM15A is replaced with a wideband superregenerative RF receiver (RM1SG), can report RF from other RF devices in the 305-325MHz range. NOTE: Unlike the superheterodyne receiver, the referenced superregenerative receiver does not work well with a wideband preamp. Both can be improved with a more efficient antenna.

The advantage of using the ZX-328n is that it costs $10, has a serial bootloader and the compiler is free. ZBasic is patterned after VB. The source is compiled to native AVR ATMega code so it runs quite fast with the 14.7MHz processor speed. ZBasic has low-level interrupt-driven X-10 send and receive that operates in the background.

NOTE: This approach retains the CM15A's isolation from the mains voltage and does not affect the FCC approval.

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