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X10 home automation with Raspberry Pi: heyu

I never quite get the hang of setting timers for lights. Either I forget daylight savings completely, or I set something so general that I find the lights coming on mid-afternoon when it’s still light. Minor annoyances require the over-application of technology, and fast!

I scored an X10 ActiveHome Starter Kit for cheap(ish) on eBay. X10 is a pretty old technology (1970s! Scottish!) and has some severe limitations (slow! prone to interference! unencrypted!) but has a large user base, and did I mention it’s pretty cheap?

The key component of a computer controlled X10 system is the CM11 computer interface. It takes serial commands from a computer, and pushes them out (slowly) as signals modulated over your house wiring. Various plug-in modules pick up these signals, and if the device address in the command matches that of the module, the module turns on (or off, or dims).

Since the version of the CM11 interface that I have is serial, I’ll need a USB→Serial converter. All I had lying around was a very old Prolific PL2303 interface, which works fine with Raspbian, but I’d prefer an FTDI one for more reliability. Long-term stability of USB Serial on the Raspberry Pi is currently questionable; there’s some good discussion on kernel parameters that might help.

To send X10 commands from a Raspberry Pi (or indeed, any Linux computer) you need heyu. You have to build it from source, but the instructions are clear, and it takes about 10 minutes to build on a 256 MB Raspberry Pi. The install script asks you where your serial port is, and for my device it is /dev/ttyUSB0.

(Update: I re-imaged the Raspberry Pi that runs these tasks today and rebuilt heyu without success. Don’t assume you can do a ./configure; make; sudo make install here. You have to run heyu’s own ./Configure.sh first before make. It does some non-obvious magic. Read the README and you’ll be fine, unlike me …)

Most of the lights in our house are fluorescent, which is a problem for the standard X10 lamp modules. CFLs are not dimmable, and the standard lamp module doesn’t work with them. The lamp modules don’t work very well with low-voltage halogen lamps, either; extreme buzzing ensues, with a faint brownish light oozing out from the bulb and a vague burning smell. Best avoided, and better to use an appliance module, which is a simple mechanical relay.

The only controller that came with the kit that would work with my lights was the X10 transceiver, which also includes an appliance switch. I gave this device an address of H9 (house code H, unit code 9), and plugged in a lamp. To turn it on, I issued this command:

heyu on H9

After about 8-10 a couple of seconds and a loud CLUNK from the controller’s relay, the light came on (if it’s taking longer, read this comment). To turn it off, I told it:

heyu off H9

Whoa! Raw power! I can now turn AC devices on and off from my Raspberry Pi (Martin Creed, watch out!). I guess I could set up cron jobs to control the lights, but cron doesn’t know about solar time (Sunwait and SunCron do, if you want to futz with them). I’ve got MisterHouse running on the Raspberry Pi for more clever control, but more on setting that up later.

Incidentally, if you’re in Europe, Marmitek sell a variety of 220 V 50 Hz X10 modules. Their website is much clearer than the angry-fruit-salad that is x10.com. It looks like X10 have updated their starter kit to include the newer CM15 USB interface which will likely not work with heyu.