Xtend: The X10 to UNIX controller

by David Shaw

Frequently Asked Questions

  1. What systems does Xtend work with?

    It should build under anything even vaguely POSIX-ish. (eg, Linux, BSD/OS, NetBSD, OpenBSD, Solaris...)

  2. How come when I start the program for the first time there are a bunch of hits immediately?

    If nobody is listening to the CM11a, it saves up a few bytes worth of messages. As soon as any program starts listening to it, it dumps them to the computer all at once. This is actually a feature when you think about it.

    The CM11a only has 8 bytes of memory for this, so the best you can hope for is 8 commands waiting for you. However, since most commands are two bytes long (eg, "Address A2", then "Turn A on"), this can be as low as 4 commands.

  3. Some X10 controllers allow you to turn things on in groups (eg, "turn a1, a2, a6, and a14 on". Does that work with Xtend?

    Yes. The X10 protocol doesn't actually have commands to turn a particular unit on. Instead it sends two commands, one to "address" the unit, and a second one which is a general "on" for that house code. Thus to turn on light a2, the controller sends "address A2", and then "house A on". Xtend emulates the X10 protocol in software, so it works the same way.

  4. Is there any way to make Xtend respond to commands faster?

    Performance-wise, letting Xtend talk directly to the serial port is better. (eg, "port /dev/ttyS0" or whatever). If you use it with the "File" option and heyu, incoming X10 commands will have to go through the heyu monitor, into the file, out of the file, and into Xtend.

  5. Why is it when I push the dim or bright button on my transmitter twice I only get one dim or bright response on the computer end?

    The CM11a is trying to help you here. If it sees two dim or bright commands happening within a short duration of each other, it will translate that into one larger dim command. For example, if you send "dim 5%" twice, the CM11a will see that as "dim 10%". There is no way to tell it not to do this, so dims and brights are inherently less accurate than plain ons and offs.

  6. When I turn on two items that print to the screen at the same time, the display gets all messed up.

    It's a feature, not a bug. The program runs your command lines in the background as fast as possible. There is no guarantee which command line will get the processor first.

  7. How come Xtend only responds to X10 commands received from the outside, and not ones generated from the CM11a (eg, using heyu)?

    There are some implications that are not necessarily good if this is allowed. For example, what would happen with a command that read "a2 on heyu turn a2 on" ?


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