Difference between revisions of "CM11A"

Revision as of 19:52, 15 June 2008

For setup information see CM11

Description

CM11A is a device that uses theX10 protocol to control lights (and maybe other stuff) around the house by transmitting data over powerlines.

Each X10 device has an address formed as housecode[A..P]+unitcode[1..16]. Becuse powerlines are often shared by neighboring houses and apartments, it's a good idea to choose a housecode different from your neighbor's. Otherwise, purchase and properly install a filter.

To control those devices you will need a small interface box which is connected to computer (the CM11A)). With it you can send commands from the computer to the devices.

The command usually consist of a few bytes (the command itself and the address of the unit to control). An exchange of checksums is needed because the lines are often noisy and commands may not be received correctly. In noisy conditions, retransmission is required by protocol.

There are several commands that LinuxMCE's CM11A wrapper implements:

• CMD_Generic_On will send x10 ON
• CMD_Generic_Off will send x10 OFF
• CMD_Set_Level depending on the existing level. The requested levels will send DIM or BRIGHT.

Some devices may send commands to CM11A device (mostly motion detectors or some other bidirectional devices). We don't have any in our office, so even if the code exists, we were not able to test it properly. It should be able to send a SensorTripped event.

Implementation notes

• CM11A is responsible for sending commands from LinuxMCE and transforming them into X10 commands
• DevicePoll will perform the communication with peripheral devices (sending commands, checking checksum, etc). It will also process any InterfacePool requests coming from bidirectional devices.
• Message will transform the unit code. For example 'A9' will be converted into the internal X10 code '67'. Don't ask why -- the translation is required by the protocol.