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[bkenobi]

Can the CM17A send extended codes?  I have a project running on an Arduino that uses a CM17A to control a couple fans (yes, same project).  The standard commands work fine and everything seems to work well in my semi completed state (the project correctly controls an appliance module and RR501 with light and desk fan).  What I'm considering now though is the possibility that a thermohygrometer (DHT11) could fail at some point.  These are cheap sensors and I've not seen an MTBF, so I'm thinking that planning for failure is a good thing.

What I'm considering doing is using extended commands to send the temperature, humidity, and/or error state of each sensor.  I already have an AHK script running on my HA PC, so adding a module to convert these extended codes to something meaningful would be easy.  I'm not sure if I'd want to post these readings to cosm or just a text file.  I'd also send myself an email or sms if a sensor was chronically sending bad readings.  But, all of this hinges on using extended codes with the CM17A on the Arduino.  I'll look into writing the extended codes library myself if I can figure out if it's possible as right now no libraries include them.

[bkenobi]

I had done a lot of searching on this topic in the past, but ran across a very useful thread on this forum.

http://forums.x10.com/index.php?topic=27283.0

Once again, dhouston had answers to my questions.  He posted several documents including the CM17A transmission protocol.  

ftp://ftp.x10.com/pub/manuals/cm17a_protocol.txt

Reading this document, it's clear that the firecracker does not have any extended command capability.  It can only send On/Off/Bright/Dim commands.  Since, there is no mention of extended codes so I suspect that it would be a major undertaking to get them working (since they don't exist)!

[dhouston]

AFAIK, there is no standard RF protocol for extended codes. The IR7243W (X10 Europe) and IRRF7243 (Marmitek) receive extended codes using a protocol that Laser Systems developed for the IR543AH/IR7243AH but they expected those extended codes to be sent from European remotes (e.g. Philips Pronto) and they only incorporated extended dim codes, IIRC.

Since you are also playing with the Arduino, you might find code for the DHT11 there that you could adapt using readily available 315MHz or 433.92MHz transmitters/receivers, creating your own protocol if needed.

[bkenobi]

I had considered that as a possibility.  I did order several of the RM1SG receivers, so by purchasing a transmitter as well, I could transmit to one of those.  I was planning on modifying at least one of those receivers to work with X10 310MHz  Not sure if modifying a transmitter to 310 is a good idea since the mod requires a hardware change.  On the up side, all of these components are really cheap except for the wait time in shipping.