# Erlang X10 Firecracker (CM17A) Interface

An Erlang interface to the X10 Firecracker (CM17A) home automation
RF transmitters.

# BUILD

```
$ rebar3 compile
```

# OVERVIEW

* Switch on a device attached to A1 using /dev/ttyUSB0

```erlang
cm17a:command("/dev/ttyUSB0", $A, 1, on).
```

* Generate and save the list of instructions for toggling the serial port

```erlang
On = cm17a:insn(cm17a:encode($A, 1, on)),
Off = cm17a:insn(cm17a:encode($A, 1, off)),

{ok, FD} = serctl:open("/dev/ttyUSB0"),
ok = cm17a:send(FD, On),
ok = cm17a:send(FD, Off).
```

# DATA TYPES

```
fd()

    An NIF resource returned from serctl:open/2.

cm17a_code = 65..80

    The CM17A house code. Valid values are in the range $A to $P.

cm17a_device = 1..16

    The CM17A device code.

cm17a_cmd = on
    | off
    | bright
    | dim
    | all_off
    | all_on
    | lamps_off
    | lamps_on
    | pause

cm17a_insn = {Ioctl :: non_neg_integer(), Arg :: non_neg_integer(),
    Delay :: Timer:timeout()}

    An instruction for the serial port.
```

# EXPORTS

```
command(SerialPort, Housecode, Device, Command) -> ok | {error,posix()}

    Types   SerialPort = iodata()
            Housecode = cm17a_code()
            Device = cm17a_device()
            Command = cm17a_cmd()

    Send a command to the X10 firecracker controller.

encode(Housecode, Device, Command) -> binary()

    Types   Housecode = cm17a_code()
            Device = cm17a_device()
            Command = cm17a_cmd()

    Encodes the CM17A command.

insn(Bytes) -> Insn

    Types   Insn = [cm17a_insn()]

    Generates a representation of the state of the serial port for
    each bit in the encoded command.

    insn/1 calls into an NIF to retrieve constants for serctl:ioctl/3
    so the result is not portable.

send(FD, Insn) -> ok | {error,posix()}

    Types   FD = fd()
            Insn = [cmd17a_insn()]

    Performs the actions in the list of instructions on the serial
    port.

        {ok,FD} = serctl:open("/dev/ttyUSB0"),
        cm17a:send(FD, cm17a:insn(cm17a:encode($A,1,on))).

    Is equivalent to:

        cm17a:command("/dev/ttyUSB0", $A, 1, on).
```

# REFERENCES

* CM17A protocol

  http://www.linuxha.com/common/cm17a.html

* bottlerocket

  http://www.linuxha.com/bottlerocket/

* flipit

  https://code.google.com/p/flipit/