I apologize but you are missing the big picture..
I have a CP290 and it interfaces via RS232 to my PC with a vintage windows' program. It is not involved in my project at all.
1- When it fails as my CP290 did back in the 90s did there is no replacement available. (So if you can't buy it -make it!!!) this is why I'm doing this project.
2- If I want a command to turn off a light at midnight I send a rs232 message with that command to do that off command and the CP290 stores that command. So each and every night at midnight off goes the light. When I typically turn off my PC at 11PM I know the light will still go off at midnight because the CP290 is a standalone controller.
I sincerely hope you understand that concept.
The CM17a is NOT a controller with command memory
which holds commands within its memory it is a PC communication device
only. Your link to the CM17a description never says it stores commands because the seller lets you believe you can controller your x10 system with a PC and doesn't tell you that your PC must be "ON" to do it with their software after midnight. The CP290 is a true command controller!!! Oh by the way, try to get help form the x10 website either by phone or email after you buy a CM17a, LOL. CM17a or any x10 Communicator you have suggested is NOT a STANDALONE command memory controller.
I guess I have assumed that most people will understand the problem. I thought I explain it clearly on the Home page, um.
Should I do a webpage just to explain this dilemma .
Today I have a fully functioning x10 system with ONs, OFFs and Alarms with a CP290 and no PC is powered on. I'm making a 'CP290 "2.0" with an Arduino' controller as a REPLACEMENT UNIT. That's it.
Maybe I'll make you a web star with posting our conversations on the www.ecoXsaver.com
website. It might help others understand better
What do you think? Can I use your ZoomKat handle in the footnotes? Nice name.